Editorial
Shorter Cranks for Downhill Performance
Why have crank lengths for mountain biking been between 170 and 175 mm since the 80s? How this range was decided upon is lost to history as far as I can tell. We can however be sure they were initially chosen based on road standards, like everything in mountain biking. That means this decision-making process was guided by what was thought to be the most efficient length for pedalling, which makes some sense, but it wasn't what interested me when I began talking to Matt Appleman about crank length.
Crank-Length-P1090709-scaled-edited
Matt decided to design his own cranks and have them machined in Minnesota, after struggling to find shorter cranks for his own bike and for his frame-buying customers. Shorter arms cleared up Matt’s knee troubles, which is what sent him down this path, and he discovered that other riders benefited from lengths shorter than those that could be found from major manufacturers as well. I initially tested a set of his 165mm Appleman Cranks but after having a conversation with him, I thought it would be interesting to see how a set of 145s would work for the mountain biking I do.
I was looking to improve clearance when pedalling up janky singletrack, or when jumping on the pedals on bony descents, but I discovered other significant benefits related to bike handling that would apply to anyone riding intense technical terrain, especially going down. This relates to the fore and aft distance between our feet, a span is determined by the length of our cranks, which I will circle back to. When you think about it, if there was some handling advantage to offsetting our pedals, motorcyclists would have figured this out years ago.
On my first ride on the 145s, I immediately noticed the absence of leverage while pedalling. In fact, I felt like I was riding a child’s bike and spinning far too quickly. I got used to it soon enough, without enjoying it, and you’d better be strong if you are turning short cranks and climbing singletrack, particularly power moves or short steep sections. I found myself running out of gears on the trail, even with a 52t cog matched with a 30t chainring. I also didn’t want to raise my saddle to compensate for the 20mm in leg extension I lost with the short cranks, which would have left my dropped saddle too high for comfortable descending. I could have dealt with this with a 240mm OneUp Dropper (assuming I could have pushed it deep enough into the frame) but I only had a 210 on the We Are One Arrival I was using to test the cranks.
I was riding the 165s here. I didn't know it yet, but I would have preferred the 145s with this exposure.
While the climbs were challenging and a little comical, the descents felt really good. It seemed I was able to be more dynamic and mobile on the bike. I was also more stable, and my confidence soared. When I got home, I played around with some movements with different foot placements and discovered something I’d never considered before. When our feet are parallel, as they would be on motorcycle pegs, our ability to flex our knees and ankles is at its maximum. From that point, every millimetre we move our feet further apart impedes that flexion, along with our ability to generate power through the pedals while descending by using our largest muscle groups.
We do this all the time while we are going down a trail, pre-compressing before an obstacle so we can unweight, but the clearest example is a bunny hop. The more we are able to flex the joints in our legs, the more power we can generate to get the bike off the ground. If you are flexibility challenged at the ankles, hips and knees, longer cranks will have an even greater impact on your ability to compress deeply enough to generate sufficient force. Trailing ankle mobility is particularly important here.
As the fore-aft distance between your feet increases, your rear ankle flexes forward more at rest, leaving less flexion available to preload the bike for an obstacle. You can easily try this on any flat surface. Start with your feet side-by-side and compress your lower. legs. Repeat this while incrementally moving them further apart, pushing your preferred front foot forward. To get a better idea of what this is like on the bike, do it with a pair of flat pedals on the floor and estimate the Q factor of your bike (distance between your pedals left and right) as well. Exaggerating the distance between your feet fore and aft will make the impact even more clear.
When our feet are closer together, it also makes our legs effectively longer, increasing the space we have to angle the bike left and right to make quick direction changes, to corner or to avoid obstacles. A counter to this is that, while your rear leg will have more flexion available, it may interfere with your saddle when cornering to that side, depending on your riding style, physical measurements, bike size and geometry and saddle position. I didn't find this personally though.
With 165mm cranks, measured centre to centre, your pedal spindles will be 330mm apart. With 145s that distance shrinks to 290, a predictable 40mm closer together. It seems like a small amount, but try and do a squat using the procedure above (with or without Q-factor included) and see if you can feel the difference.
Parallel feet moto-style. These images don't make it easy to see a difference in flexion between the three positions, but it's easily felt. Photos - Cristina Piccone
With the Appleman 2XR 145mm cranks.
With the Appleman 165s.
Balancing is easier when your feet are close together and so is weighting your feet evenly fore and/or aft and left and right - or accurately weighting one more than the other. Ask any moto rider what they’d think about having their feet offset right to left and I think you get the idea. And in terms of jumping a hip, doing whips or tables and cornering, everyone has a good side that is related to which foot is forward (your rear foot is the critical one in some cases as well). Reducing this offset would diminish the gap between your good side and your bad side.
I had theories after my experience riding both crank sizes but I hadn’t tried them back-to-back, which is the best way for me to determine if a hunch has any merit. I threaded identical pedals into the two sets of cranks and, with the 165s mounted, I did a couple of laps on lower mount Fromme. The lap consisted of Bobsled, a bermy flow trail, followed by a short climb to Upper Griffin, which is more technical and a little janky in places.
My lap on the 165s felt fine and I rode Bobsled, as I usually do, as though I was chainless, working the backsides of rollers and trying to stay on the fastest lines. At the bottom, with my son taking a few photos, I swapped the cranks, with the pre-installed Crankbrothers Stamp 7 pedals, in about four minutes, including torquing each arm and spindle bolt to spec. We pedalled back up and I immediately remembered what I don’t like about the 145s. Spinning tiny circles feels really weird at first. Losing leverage is a bit like losing time because the period in which your pedals are in an optimal position to deliver torque is noticeably reduced. I did the climb one gear lower however and spun a little faster cadence. The other side of that reduced torque window is a briefer dead spot before, during and immediately after the 90º position. Higher RPMs and shorter cranks together make spinning circles easier and more efficient.
All you need to remove or install Appleman 2XR cranks is a 5mm hex, but this is one of those cases where I prefer to use a torque wrench if possible. The cranks are held on with a pinch bolt, after being pressed into position by spindle bolts. If you over-torque the spindle bolts it will put too much pre-load on your bottom bracket bearings, slowing you down and increasing wear. It still took less than five minutes to do the swap. Photo - Luca McRae
Once I began my second lap of Bobsled I remembered why I liked the 145s so much for descending. I felt planted, stable, and a little more in control. I also found myself more likely to pop off little hits and get a little loose. There was no question that I felt better descending on the shorter arms, and I was having more fun as well. It felt a little like the way I feel if my body is in better shape because of any kind of complementary activity or training.
The difference was significant and while I didn't feel terrible at all on the 165s, I felt much better on arms that were each 20mm shorter. So much so that, if I was going to put together a dedicated park bike, there is no question I’d be reaching for a pair of short cranks. If I was racing DH the calculation gets a little more complicated, but maybe not drastically so, considering the speeds of DH racing. Perhaps you’d simply need to choose your gearing a little differently to ensure you could generate power when needed.
This has me curious about what might be the sweet spot for me; 155mm cranks like those that shipped on the Hope HB916 that Graham Driedger enjoyed so much. While leverage changes related to the length of a lever decreases in a linear fashion, unlike wind resistance or rabbit populations, as cranks get shorter, each 10mm change represents a larger percentage of the remaining length. I’ve never noticed 165mm cranks being too short to generate the appropriate torque compared to 170, but dropping down to 145 made a massive difference in pedalling situations where a lot of power needed to be generated quickly. The other factor the 155s would mitigate some is the need to raise your saddle to get appropriate extension at the bottom of your pedal stroke.
Graham was quite keen on the 155s. Here’s his articulate description of the benefits he experienced: “The Hope Evo 155mm cranks position my feet in more of a neutral stance compared to regular 170mm cranks, with less noticeable tension in my hips. Riding switch-footed felt far less alien than usual, as I lazily bumbled through janky terrain. I can't recall a single crank-arm strike - the crank ends confirm that - and they're machined closely to the pedal threads with just enough meat on the ends for structural integrity. I think shorter cranks should be considered by many riders, gravity focused or not.”
I generally only switch to right foot forward when my legs get tired on a long descent, but when I do, it feels like my feet are very far apart indeed and that my front foot is much too far forward. With shorter cranks, riding switch-footed indeed feels, in Graham's words, less alien, and I could do it comfortably on the 145s.
I liked these cranks independent of their length. They are easily installed and adjusted and are machined in Minnesota. They look pretty cool too, although the painted finish wasn't quite up to a North Shore winter.
I am quite convinced the benefits of shorter cranks for downhill performance are real, but that's not science. While I like to go as fast as possible in a given situation, I don't time my rides and my racing days are probably over so I don't have evidence of these benefits on the clock. While I have spent a little time on the bike thinking about what works and what doesn't, feel free to take my impressions with a grain of salt.
Further, this obviously isn't for everyone. While the findings related to crank length and performance rarely show an advantage for longer cranks, in some situations they are obviously superior. If you ride a single speed or, god forbid, a fixie off road, those long arms are essential. Some riders prefer to climb in taller gears and if you are riding up steep singletrack, long cranks allow you to push a larger gear on the cassette, giving you a reserve and keeping you out of that fast-wearing largest cog.
If you put more focus on downhill performance than pedalling, particularly on steep or technical terrain, or if you like to jump, or ride bike park, I think this is worth a look. Hopefully some of the larger manufacturers will get on this train, but for now, one place to get short(er) cranks is Appleman (155, 145 and 135mm) and another is Hope (155). North Shore Billet's recently-announced Talon cranks are available in both 155 and 160mm.
Height - 6'/183cm (mostly legs)
Weight - 170lbs/77kg
Inseam - 33"/84cm
Ape Index - 0.986
Age - 58
Trail I've been stoked on lately - Sam's Dad's Trail
Bar Width - 760mm
Preferred Reach - 485-500mm (longer with 27.5 wheels than 29)
Comments
Cooper Quinn
9 months, 3 weeks ago
Eventually as cranks on ebikes continue to shrink they'll just be little nubs to stand on. Like some kind of a vestigial peg on each side?
This will necessitate some form of power control device on the handlebars.
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Kos
9 months, 3 weeks ago
Came here to say this! Footpegs! Braap?!
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Andrew Major
9 months, 3 weeks ago
“If you ride a single speed”
NSMB, on the surface a descending-first North Shore Freeride e-magazine, secretly and subversively the last mainstream mountain biking publication that can’t go a week without mentioning single-speeding!
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DanL
9 months, 3 weeks ago
I ride a single speed DH bike, so it now seems like my niche antics have just been targeted
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Vincent Edwards
9 months, 3 weeks ago
I wonder what would happen if you could drop the BB instead of raising the saddle to account for shorter cranks (Or maybe split the difference) ?
Lower BB = more planted and ‘in the bike’ feeling while descending. Yes you would give up on gains in terms of fewer crank strikes… but it would be interesting to do the testing. This would also shift the relationship of your seat to your bars… when standing the bars would feel ‘effectively’ higher.
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Moritz Haager
9 months, 3 weeks ago
But that would negate the benefit of fewer pedal strikes, no?
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Vincent Edwards
9 months, 3 weeks ago
Yes- I'm specifically interested in a compromise approach where the BB drops about half the difference in crank length. (so if going from 175 to 160mm, you would lower it by 7.5mm)
IF pedal strikes were the limiting factor for BB drop with 175 cranks, then moving to 160 or 165mm cranks would allow the option of a lower BB **if the benefits of lower CG are preferable to the benefit of fewer pedal strikes.
Just about every geometry choice is a compromise between different attributes. A 70deg head angle is great on tight level trails. A 60deg head angle is awesome for steep fall line downhills. Most of us ride something around 65deg these days.
Sidney makes a good point about the chainring being closer to the ground. I suppose designing a bike around shorter cranks would also mean designing around a smaller chainring (like a 28) to combat the leverage change. This would help a little bit with the clearance issue.
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Sidney Durant
9 months, 3 weeks ago
This is what I did when I built up my most recent bike. Having previously experimented with 150 cranks, I decided to build up my Pivot Firebird with 27.5 wheels front and back (dropping the BB ~18mm) and put on 145mm cranks.
I'm 6'4, and would not have been happy with such a setup back when a 170 dropper was considered long, but with a 240 one-up dropper replacing my previous 210, and a 30t chainring instead of my regular 32t. I've found that for 95% of my riding, everything is better about the new setup (except the small wheels, I have some mixed feelings there).
I've found two disadvantages.
First, big 'oomph' moves on the climbs. Sitting and spinning at 100rpm feels and looks a bit silly, but I haven't noticed a difference in times or fatigue when climbing, and moderately technical stuff is generally easier to get through with the additional clearance. However big pedal kick moves to get up a 2 foot ledge from a track stand (or similar) are harder. If there's only room for one pedal stroke, I can't get as much power in that one pedal stroke.
The second is descending through *large* chunk. I'm not talking about descending through baby heads, but through volleyball sized rocks. In these scenarios, where you have to worry about clipping pedals even when your pedals are level, the lower BB is a disadvantage (note that when pedals are level, the shorter cranks don't give you any additional clearance). And the chainring starts to get in the way too.
One thing that would help with this is keeping the same geo, but running a 29er rear wheel. This would help in two ways - first, I'd be able to drop down another chainring size, to a 28 tooth. Second, a larger rear wheel means the leading edge of the tire is closer to my chainring (assuming the same chainstay length), and so chainring strikes would in theory be less common.
However, pedals will still be closer to the ground when riding with level pedals, so that's a definite trade off.
Overall, for me, short cranks combined with the low BB are worth it, even at 6'4", and without an ideal setup. If I could get a 160mm 29er with a 330 BB height, and a 28t chainring+bashguard, and run 145s, I think that would be ideal for the winch and plummet riding I often do.
Although I also think this setup may make even more sense on a short travel trail bike, where you may be riding high speed flow trails and want the low bb, but don't often ride trails with volleyball sized rocks so the disadvantages won't matter.
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Tommaso Gomez
9 months, 3 weeks ago
Hey Sidney, it's been a minute! So I actually run 165mm cranks on a 160f/160r RocketMax with the choice of a 331mm BB height as a mullet (63HTA) or a 343mm BB height as a 29r (64HTA). The super low, slack mullet setup is amazing as a winch and plummet stuff like Pacifica. Everywhere else that's less steep and more pedally (and especially anywhere with tech climbing like Tahoe), Id rather run the taller 29er and not get destroyed by pedal strikes. I thought about running shorter cranks on the mullet, but at 5'9", I don't want to sacrifice any dropped saddle clearance.
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Sidney Durant
9 months, 3 weeks ago
Oh hey! Hope you're doing well. What you mentioned about the dropped saddle clearance is why I mentioned moving to a 240mm dropper post. Room to move around on the bike is very important to me. Fortunately I didn't feel limited with a 210, so figured if I switched to a 240 and ran short cranks I'd still have enough clearance. But depending on your frame and dropper you may not be able to fit a longer dropper, even after you raise the saddle slightly to adjust for the shorter cranks.
For me, the 330 BB on the 165mm travel bike has the feeling I want for steep trails and flow trails (amazing at winch and plummet) while the 145 cranks keep my pedal clearance where I need it (the same as the stock bike with 170mm cranks)
One thing to note is that my setup (full 27.5) doesn't have the additional slack-ness of your mullet setup. I find that too slack a head angle makes a bike feel unwieldy on climbs, and that may be part of what you're not liking with the mullet setup when climbing.
Also, I built this setup when it was my only MTB, but knowing that I had plans to get a light trail bike which I got a few weeks ago. I'm running 165 cranks on the light trail bike now and have been riding it exclusively as when I took the big bike in for service they noticed the frame was cracked, so I'm waiting on the carbon repair. Anyways, I don't mind not having the short cranks, but I do miss the low bb. For me the cranks are mostly a means to an end (low bb), and not a huge win on their own.
If you want to try (and have a threaded BB to make the swap easy), the Canfield cranks are relatively inexpensive and go down to 150mm. I'd let you borrow my set but I sold them to a friend.
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roil
9 months, 3 weeks ago
Who makes your 145mm cranks?
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Andrew Major
9 months, 3 weeks ago
Hedging here to come back a few years down the trail and revisit where the short crank trend has gone:
“Lower BB = more planted and ‘in the bike’ feeling while descending.”
I’d argue that this is proportionally more true the shorter the rear-center of a bike becomes and as bike design drifts outward from the competition for most-tucked rear wheel it’s less relevant.
As chainstays get physically longer, and ever-longer stays become the new trend, BB height will rise and I predict a lot of folks operating on their own steam will return to the traction control and stability of longer crank arms.
In the long run, the best thing about all the short crank experimentation going on (and here’s my hedge) is that parents are going to be able to pick up sweet 135-155mm crank arms cheap for their kid’s bikes.
…….
In terms of folks who will stick with short cranks, it’ll be interesting to see what % of them ride e-bikes. Every short-crank evangelist I know personally spends a lot of their riding time on a BroPed and that makes me think there’s a degree of transferability/learned behaviour that needs to be accounted for there.
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Jerry Willows
9 months, 3 weeks ago
Paul Aston has made comments (take them for what they are worth) that 29ers have a huge BB drop (compared to 275 or 26) that manufacturers could raise the BB and still be "planted".
Would be a good experiment
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Sidney Durant
9 months, 3 weeks ago
Yeah, he also rides a huge bike, in reach head angle and basically every metric. Makes sense to me that he has the stability he needs and can therefore run a higher BB. And I respect where he's coming from, and think that for going fast through sufficiently rough tracks, his setup makes a lot of sense (375 BB height IIRC). But for me that just sounds like riding a barge, and it's not what I want *for my local trails that I like to ride*.
For bike park tracks? Sure, I'll take a tall BB, long chainstays and a 63 degree HTA. I have all the space in the world to setup for that next corner.
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Andrew Major
9 months, 3 weeks ago
It’s been very interesting going from my Walt V2 to the Banshee Enigma. Say what you will about rigid forks (#JerryWillowsHatesMyBike) the setup really isolates the effects of chainstay length (463mm vs. 418mm) and BB height.
If I was redesigning the V2 I’d absolutely go higher for the BB height (less drop) if keeping the rear center.
I think it would be fun to have a FS test mule with sliders and an eccentric BB to play with this stuff.
———
I should say there’s nothing original about my thoughts here. Folks have been predicting a move to longer stays and higher BBs for years now. At least for FS bikes.
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AndrewR
9 months, 3 weeks ago
And Pole have raised the BB height/ reduced the BB drop on their new bikes.
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roil
9 months, 3 weeks ago
I suspect Pole's higher BB is because of the 190mm travel front and rear. ~30% sag on 190mm combined with a -30mm BB would have the bike VERY low.
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Sidney Durant
9 months, 3 weeks ago
I've only ridden an ebike once so that's not where I'm coming from.
I'm not sure I agree that longer cranks provide more "traction control and stability". Can you elaborate?
I do agree that with long chainstays, BB heights will probably rise, but I'd attribute it to needing to keep the chainring out of harms way now that wheels are so far apart that you can fit increasingly large rocks between them, and you need the chainring to be tall enough to not scrape on those rocks.
For "go fast in a straight line" riding, a high BB and very long chainstays make sense to me. When turning, I also think proportional chainstays still make sense. They make it easier to get the weight onto the front tire.
But when turning, I also prefer a low BB. Nothing feels better to me than quick successive turns. Think 50:01 rut track style riding. And for that a low BB is amazing, imo. I really feel like it's quicker and easier to get in and out of turns with a low bottom bracket. And when riding steep trails with catch berms, I find that it's a very noticeable advantage for me.
The low BB also gives fore-aft stability (ie combats the willingness of a bike to otb). Which to me means I can get away with a slightly smaller bike (in reach and head angle) which means that the chainstays can be shorter as well, and now I have a bike that's stable in the ways I want (front to back when pushing through my feet) but that can turn on a dime. And because of the reduced reach it's also easy to get into a manual or endo or whatever. It's great fun
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Andrew Major
9 months, 3 weeks ago
“I've only ridden an ebike once so that's not where I'm coming from.“
There’s exceptions to every rule etc. but in this case I’m just talking about short crank evangelicals I know riding bikes where I ride bikes and all of them spend a lot of time on e-bikes.
“I'm not sure I agree that longer cranks provide more "traction control and stability". Can you elaborate?”
I doubt that most folks engaging with this thread agree with me at all. I put the comment here to come back to in a few years when I’m hedging that more than a few of them will.
I’ve experimented a lot with crank length, and oval vs. round chainrings. I’ve even run 180mm cranks for a few years despite my legs being too short to sit and spin nicely with them.
Lately I’ve been back and forth a ton between 170mm and 175mm cranks on otherwise identical bikes.
With the caveat that I like to climb technical trails as much as I like to descend, I notice that a longer crank arm allows me more control over torque and traction than a shorter crank arm, for example pedaling up loose baby heads. I fine it works better for ratcheting and power moves from a stop (track standing) as well. Again, not down to claims of more or less power but controlling said power.
Stability. In addition to better balance climbing out of the saddle. Descending, I find, even accounting for needing to run a longer dropper with shorter cranks and steeper STA, that the wider stance of 175mm cranks works better for me turning and creating motion than a narrower, more moto, stance on shorter cranks.
I have significant hours on cranks as short as 165mm but do note that haven’t bothered to try shorter based on my 165/170/175 experiences.
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Cee Cee
9 months, 3 weeks ago
Thus spake a hardtail-predominant pope of singlespeeding, recently recovered from overtorqued Achilles. Why describe 165mm crank as 'short'?--cranks are different lengths.
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Andrew Major
9 months, 3 weeks ago
“as short as” not ‘short’.
…
What length of cranks are you currently running on self-powered bicycles @Ceecee?
Easy enough to meet back here in five years and revisit.
I’m always happy to be wrong about predictions on the future of mountain bicycling.
Cee Cee
9 months, 3 weeks ago
From the top of your comments above: 'short, shorter, longer, ever-longer, longer, long, short, short, short-crank, longer, short, short, longer, shorter, longer, shorter, shorter, as short as, shorter'
If you keep it up, I'll be forced to re-name your region North Short or North Ever-Longer or North-by-the-Word. May happiness be yours
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Justin White
9 months, 3 weeks ago
I can argue for short cranks providing more traction control. (The shorter-crank hype machine has provided a ton about stability, as have I down below, so I'll leave that alone here)
With shorter cranks the instantaneous torque is less but you get back to it faster, so the overall torque is more consistent (a graph over time would have lower peaks and narrower valleys, a flatter curve overall). The "getting back to it faster" is what I really love, and where I feel the control comes from. I feel less like I have to immediately get back on the power as soon as each foot comes slowly back over the top of a longer crank, or risk stalling out and then having to just lean on the front pedal, which ends up spinning the tire thanks to the long lever.
Could liken it to traction control in a car. The faster the system can adjust the power, the more power can be put down. One reason electric cars can accelerate so fast is that the feedback loop of the traction control system is very tight, because doesn't have to deal with the hysteresis inherent in a combustion engine it's entire drivetrain. Yes, electric motors have stupid torque from 0 rpm and that's part of it, but if you just dumped that to the ground from a dig, the tires would melt off immediately. However, since the power control isn't adding or subtracting fuel and waiting for it to be burned and that burning then accelerating all of the reciprocating and rotating mass of the engine and trans, it's just more electrons or less electrons and they move at the speed of light, so the feedback loop is ridiculously fast. And this allows for more time spent actually putting the maximum possible power for the conditions to the ground.
But that's just me, going from 175mm to 170mm to 160mm cranks, and noticing way less spin-outs on muddy/mossy/rooty climbs (and this year especially it has been super wet where I am). Which means I'm making it further up those greasy climbs, providing ever more opportunities to not spin-out. Another nice fast feedback loop.
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Andrew Major
9 months, 3 weeks ago
@Justin, I didn't post to "argue" with any short-crank converts. It's bicycles, whatever works for you is great. And it's also great that folks are investing in playing with different setups and challenging their long-held preferences.
I made my post as a time stamp for a future piece I want to potentially write. Let's come back in a few to five years and see what length cranks you're stoked on.
------
*edit: just to reiterate. It's genuinely from a place of curiosity and bike nerdery:
"I’m always happy to be wrong about predictions on the future of mountain bicycling."
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Justin White
9 months, 3 weeks ago
I meant "argue" as in "provide rhetoric and examples, for or against", not argue like "you're wrong, I'm right".
In five years, I definitely won't be stoked on going back to 175 cranks. Unless I move somewhere with no rocks or turns, or someone takes all the rocks and turns out of my local trails.
Zero-cool
9 months, 3 weeks ago
This comment has been removed.
fartymarty
9 months, 3 weeks ago
Andrew - I can smell the upcoming marketing hype now... Geometry designed for shorter cranks, lower BB, taller HT, slacker / steeper STA (pick which ever marketeering spin you want to take)_, more ergodynamic for a better handling bike... _
The question is - who is going to do it first???
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Vincent Edwards
9 months, 3 weeks ago
This gets me thinking about the relationship between front center / rear center / wheelbase / BB… and how changing one often necessitates changing another to find a new balance.
My current bikes are in the 430-438 CS range with 460-475 Reach and 66.5-65 HA range. I agree that as you stretch out the front center, it’s generally a good idea to balance that with some increase in the rear center. I also see how the longer your wheelbase, the more you might need to raise the BB to avoid strikes… and the less you might notice negative consequences. You are raising your center of gravity relative to a bigger triangle that is inherently more stable.
Also as a caveat… my current foray into ‘short’ cranks was putting 170’s on my Ripmo. So I came here to read about Cam’s experiences and speculate a bit. I hope to try 165 and 160mm cranks… but probably not on my SS. I’m much too focused on pedaling, climbing, and navigating technical XC-type trails to justify short cranks given the drawbacks Cam mentions here.
Bracketing is a really good means of testing, until you aren’t controlling for other elements of design that might need to change along with an extreme change (like 155mm cranks)… then it’s hard to get the complete picture. I tend to agree that cranks shorter than 160mm will likely stay ‘niche’ (except possibly in DH racing)
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Marc Pfister
9 months, 3 weeks ago
MY CRANK LENGTH
WAS AN HONOR STUDENT
AT CENTRAL JR HIGH
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SilentG
9 months, 3 weeks ago
Random data points from someone who went from 175mm to 165mm and has been goofing around with a 155mm...
Lots of people - we will call them 'me' - forget to adjust the seat height slightly up as the crank gets shorter.
With the 155mm I also adjusted my seat slightly (4-5mm, maybe less) forward which made a big difference.
Also the recommendation I saw somewhere was to go down a chainring size at 155mm.
For me that is a 30T 11-42, maybe an 11-46 in there 11 speed setup for 165mm cranks and a 28T for the same on 155mm cranks.
It has been several years since I went from 175mm down to 165mm but I find no loss of power or not enough to care about, less worry about banging the cranks on rocks and debris, etc and the coming down part feels nice and centered on the bike.
155mm has been a bit more of a mixed bag at first - on one hand I feel like I can pedal for days with the shorter crank length but moving the saddle slightly forward cured what felt like was just enough slightly less torque related issues in technical uphill stuff.
The different lengths can also hit different muscle groups in your legs which can be a pro or a con depending on your setups.
About me - I'm a Libra, I enjoy walks on the beach, I'm 5'10 tall with a 32 inch pant inseam with slightly longer than average ape index.
YMMV but no regrets on going to 165mm on all my bikes and I'm fine with continuing the 155mm experiments as I don't get a twitchy eyelid, go to the fetal position, or anything when I think about riding that bike vs the 165mm cranked bikes I have.
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JT
9 months, 3 weeks ago
We're pretty much spot on dimensionally and zodiac wise. Of course I'm gonna agree with most of what you wrote.
As I blabbed on the last piece on Appleman cranks, I have been loving 155s. I haven't found that situation where I wished I had longer cranks. Building a frame up and I'm using the 170 take offs from one of my bikes. It'll be interesting to back to back the bikes and really grok things.
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Justin White
9 months, 3 weeks ago
The need/want for moving the saddle forward makes perfect sense, especially if you have a bike with a slack actual-seattube-angle. With a 75 degree STA, 20mm* of raise gives about 5mm of rearward change as well.
*(However, I don't think you need to match the saddle raise all the way to the crank length reduction, see below. Probably why you don't mind when you forgot to raise the saddle at all.)
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.glib
9 months, 3 weeks ago
The obvious solution here is the dropper crank. With the push of a thumb button your cranks extend alongside your seat to 'climbing mode' with a luxurious 240mm length for maximum torque. Then when you're ready for a descent, they retract back to 0mm pegs for the descent as your seat drops.
Should be easy to prototype on a park rig with some pedals direct-mounted to a bottom bracket.
Patent pending, address your cheques to 'glib from the internet'.
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Velocipedestrian
9 months, 3 weeks ago
The talk of flexion in the ankles (specifically achilles length) is interesting to me.
In this position I can push my kneecaps ~175mm forward of my toes with my heels on the floor, and hadn't thought about it beyond the old 'Drop Your Heels' advice.
I'm not sure how to incorporate this idea yet, but it's an interesting variable.
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Justin White
9 months, 3 weeks ago
I've found that the added flexion from a narrower (fore-aft) stance makes good things happen without conscious thought. Allowing the bike the move vertically under you just happens more freely when your feet are closer together and you're that much further away from the limits of your ankles and hips. You'll find yourself blasting into some monster roots faster than usual and just find the bike magically unweighting a little bit more without you really trying. Manuals become easier since fore-aft bike/body movement is also easier. It reminds me of first getting a dropper: room to freely move about.
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ackshunW
9 months, 3 weeks ago
Good write up! I agree with Vincent though. . . Chopping 20 or 30mm off the crank length seems like a lot, while maintaining regular BB height. You alluded to it yourself, where you didn’t want to raise saddle way up there to meet “typical proper” knee extension. I think that kills it for me- my rides are much more up-and-down-and-up than winch & plummet—- and the higher seated position I’d want would be a problem. Either in the higher dropped position, or in spending more time and energy lowering the dropper that much further (everything is work right!?!?).
The other thing that gets me is powered tight technical moves. I’m so used to the power/torque curve I can eke out of a single pedal stroke on my 175’s, that anything less feels hampering. -[I did Singlespeed exclusively for a while]. I haven’t given it a long chance, and only went down to 170’s, none of this modern unicycle crank business, but my muscle memory can’t learn to use a full rotation to pop up a ledge where I’m now comfortable and able to do it with a half-rotation.
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Sidney Durant
9 months, 3 weeks ago
Your last point is the one disadvantage I've found with short cranks that I don't think I can get around. They're definitely still worth it for me, but when there's only room for a half crank to get up and over something, I miss my longer cranks.
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Justin White
9 months, 3 weeks ago
That's what gears are for. If you reduce chainring size appropriately, you'll get pretty much the same overall torque output. Yes, the rollout will be slightly lower, but half-cranking over things is much more about impulse power than the distance a pedal stroke would actually move you on flat ground.
You'll also find that many places where "there's only room for a half crank" turn into places where there is room to just keep pedaling.
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Sidney Durant
9 months, 3 weeks ago
I've made the change in gearing, and my cadence has definitely gone up since moving to shorter cranks. I'm not talking about times where I'm wishing I had a lower gear, and I've messed up my gearing.
I'm also sticking to 145's. I like short cranks.
But I'm talking about doing one hard downstroke to get the speed needed to get up a tall ledge. There's no room for two pedal strokes, because behind me there was another technical section. I can't pedal through a two foot ledge. This is not a common scenario. But it happens, and in those scenarios I just can't get as much momentum going. There are places where I wish I could get a bit more power in one continuous push of the crank. I can think of one specific move (it's after a slight endo to reposition my rear wheel, so there's no 'keeping momentum' possible) where my longer cranks were definitely nicer. But the overall technical climb (that includes that move) is definitely easier on the shorter cranks because I can pedal through certain things. But if I were 100% optimizing for technical climbing, I think I'd stick to a high BB and standard length cranks.
Also note that I'm an extreme example, at 6'4" running 145's. So many people may not experience this disadvantage as much as I do.
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Justin White
9 months, 3 weeks ago
"But the overall technical climb (that includes that move) is definitely easier on the shorter cranks because I can pedal through certain things. But if I were 100% optimizing for technical climbing, I think I'd stick to a high BB and standard length cranks."
Those don't line up. If it's overall easier on shorter, then "100% optimization" would be shorter. Longer is just optimizing for the corner cases of "that move". By that metric, "100% optimization" would actually be 185mm cranks (longest I've seen as a commonly available size) and 36T+ chainrings, not "standard length cranks".
It's also going to be easier to adapt to a need for slightly more power on the half-pedal moves with short cranks, compared to the plain impossibility of getting in continuous pedal strokes on certain things with long cranks. Evidenced by most of the world already got used to the extra power needed when the crank radius to wheel radius changed with 29ers.
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Sidney Durant
9 months, 3 weeks ago
But the "overall it's easier" part of my comment is because of the additional clearance.
So I'm saying 'big moves are easier with longer cranks', and that 'the additional clearance of short cranks makes most things easier'
So I'm saying that the best of both worlds for tech climbing would be long cranks (for the big moves) and a high BB (for the clearance).
Again, that's not what I'm running, because overall I prefer the descending feel of a low BB. But if all I cared about was tech climbing, I think I'd go back to 165-175 range cranks.
Justin White
9 months, 3 weeks ago
It's not just the clearance of short cranks that make climbs easier, it's the also the smoothness of the power delivery.
Morgan Heater
9 months, 3 weeks ago
Wouldn't it be possible to shift into a harder gear for the big moves and get the same power?
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Justin White
9 months, 3 weeks ago
That's exactly what I meant by "that's what gears are for" above.
Sidney Durant
9 months, 3 weeks ago
No, my point is that it's not something that can be fixed by adjusting the gearing. I'm in the middle of the cassette. If I wanted to, I could upshift, or downshift.
But imagine the difference between running 170mm cranks and 85mm (170/2) cranks. With 170 cranks, you pedal at 90 rpm. With 85mm cranks, you pedal at 180 rpm (at least in my experience, foot speed stays the same, while rpm changes). For climbing up a fire road, no issues here. You just spin faster and that's okay.
But now, you come to a move where there's only space for a single pedal kick. On the 85mm cranks, my experience says that that pedal kick is going to be much weaker.
Again - not a deal breaker for me, even though I love technical climbing. But just something that seems to be a slight drawback. Just because shorter cranks are better for me doesn't mean I love every single thing about them.
Justin - elsewhere in the thread you say "The smoother torque application of shorter cranks (slightly lower peaks, but especially narrower minimums)" is an advantage. Here I'm calling out that the slightly lower peak is a problem when you want that high peak, but now you're saying I should just adjust my gearing. By that logic, longer cranks would be just as good at loose climbs because you could just "adjust your gearing" to get that same "slightly lower peak"..? My point is that there's a flip side to (almost) every coin.
Some might like shorter cranks cause they're lighter, someone else is putting lead weights on their BB.
Andy Eunson
9 months, 3 weeks ago
One thing to add to the discussion is cadence. What is the optimal cadence? I have a natural cadence on the road of 90 to 100 once I’m warmed up. Slower uphill. Off road my natural cadence is much slower. Maybe 70. Especially climbing. A high cadence like 90 or so especially if it’s a bit rough will cause me to start bouncing. And high cadence means a lower gear (or higher speed) but too low a gear will make it much easier to break traction. My question is this; will a higher cadence in a lower gear with shorter cranks mean breaking traction is less likely because the cranks offer less leverage?
Much shorter cranks as Cam discovered mean the seat height has to be raised a commensurate amount and then bars too. Really for much shorter cranks you also need a frame designed for that. Lower bb drop and taller head tubes. If I put 155s on my bikes to replace the 170s I have now means a much higher seat height. And taller bars. And now my seat will be a bit further back relative to the rear axle. So a shorter stem too? Or longer because head angle and seat angle come together as the height goes up. It gets complex.
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Sidney Durant
9 months, 3 weeks ago
This comment has been removed.
Justin White
9 months, 3 weeks ago
"will a higher cadence in a lower gear with shorter cranks mean breaking traction is less likely because the cranks offer less leverage?"
I think so, and it's what I've experienced. The smoother torque application of shorter cranks (slightly lower peaks, but especially narrower minimums) I have found makes for better traction. Plus more pedal strokes gives you more chances to adjust the peak force.
I'm sure better at climbing greasy stuff with shorter cranks. It's similar to why you wouldn't want to climb something slick in a big gear. Have to push hard to make progress, but less frequently, so if the traction goes, your crank drops to the bottom and the tire spins a lot, and you have to wait to get the next leg over the top before again pushing hard, and spinning the tire, and waiting, ad defatigatio.
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Sidney Durant
9 months, 3 weeks ago
Agreed! Spin to win on loose or greasy climbs
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kcy4130
9 months, 3 weeks ago
For those curious about trying shorter arms, Appleman rents out fit cranks for one to try 100mm-175mm long arms. Rock strikes would only be a little more likely than normal 175mm crank arms. Out of stock now, but I thought it was an interesting offering for those hesitant to take the plunge of purchase. It'd also allow one try 175 arm on left and 100 on right, which I've never thought about before, but am suddenly intensely curious about.
https://www.applemanbicycles.com/shop/2xr-fit-crankset-rental/
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Cooper Quinn
9 months, 3 weeks ago
I'm not sure those are actually for outside use - my understanding is that they're to be used on a trainer for bike fit. I could be wrong, though.
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kcy4130
9 months, 3 weeks ago
Website doesn't say that anywhere, but you could well be right. Even if for actual dirt use, I'm sure there's a "don't get too sendy" clause in there somewhere. Seems like light duty single track would be fine. I mean, no one is worried that shorter cranks would impede their descending or hucking abilities. It's all about if one can still climb tech and pedal decently, that's what an mtber would be mostly testing. It's for usa only tho.
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roil
9 months, 3 weeks ago
Cam, thank you for the article. I'm your height with 170mm cranks and have been itching to try something closer to 150mm. I have always felt that my feet are too far apart on the descent, and limited my range of motion.
BikePacking.com also did an article crank length using Appleman which is worth reading (BP article). I'm not sure how long you spent on the shorter cranks, but the BP author ran each size for a week and was pretty comfortable climbing on shorter cranks after some saddle time.
Or, we could just ditch cranks for something else entirely! Building a more efficient bike - YouTube
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Morgan Heater
9 months, 3 weeks ago
I think his definition of efficiency does not mean watts in/watts out.
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Sidney Durant
9 months, 3 weeks ago
He seems to define efficiency as "more torque". By that logic, we should all be running 24 tooth chainrings all the time. Peak torque would be way higher
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roil
9 months, 3 weeks ago
I was more interested that this setup would allow you to keep your feet side by side or Moto style. Not qualified to comment on the system's proposed efficiency but I would like to try it!
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Velocipedestrian
9 months, 3 weeks ago
I'm sure you could mount something on the BB spindle to try it out if you have some coastable descents. Could go chainless too!
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roil
9 months, 3 weeks ago
This article and the comments section pushed me over the edge and I finally bought some 150mm cranks yesterday. I'll start with those but I'm not opposed to giving your idea a try in the future.
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C.C.
9 months, 3 weeks ago
Cam,
This is an awesome article. Not because it has some scientific conclusion that short cranks are better than long cranks, but rather, you have identified some noted pros and cons to each crank length.
As a rider with a much shorter inseam than you, I am curious how this same experiment would pan out for myself. Riders of all inseam lengths will benefit from crank strike clearance with shorter cranks, but do riders with a shorter inseam benefit the same way as you have described from a shorter crank length?
I have been on 170mm cranks for a very long time. My last crank length purchase I wanted to go to 165mm, but unfortunately there was no stock. Now I'm curious to try 160mm, possibly 155mm. My potential worries would be decreased climbing ability since I barely rock a sub 40 min Expresso climb, and having to raise my dropper height as my current seat tube insertion depth is pretty shallow and I'm already rocking a short length dropper.
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Justin White
9 months, 3 weeks ago
"I also didn’t want to raise my saddle to compensate for the 20mm in leg extension I lost with the short cranks, which would have left my dropped saddle too high for comfortable descending."
I don't think you need to go a full 20mm up. Certainly if you're very sure your original leg extension was perfectly optimized for max power and you don't want to lose a single fraction of a watt, then yeah, boost it the same amount as the crank change.
However, since the crank length shortening also takes effect at the top, you might find you don't need the full height change since you'll have less leg flexion overall. With 20mm less pedal radius already reducing overall leg flex by 40mm, raising the seat a full 20mm means you're actually reducing leg flexion by 60mm. This might actually be really good for someone with issues in the front of their knees, but most riders probably don't need that drastic of a reduction.
Not to mention to for a 30-ish inch inseam, taking 40mm out of the horizontal stance will raise your hips about 5mm, so even a 15mm saddle raise should give you the same fully-dropped saddle clearance with pedals at 3 & 9. Yes, you can't get as low, but you may not want to since that will require extra leg flexion, and decreasing leg flexion is arguably a good part of the goal of shorter cranks.
When I shortened by my cranks by 10mm to 160mm*, I only raised my saddle by about 6mm. I don't need the full 30mm of less leg flexion, and the 25mm-ish I got feels great already. As well, I don't really notice a detriment from the 4mm less leg extension. In fact, I think I like it because that last few mm of extension usually comes from the ankle, and saving ankle strength for handling big (flat) landings is a nice bonus. I can very slightly tell that the saddle is a tiny bit closer at full 180mm drop, but only if I go from full sitting to full standing on purpose and think about it, don't notice during riding.
tl;dr: When shortening cranks, try doing a saddle raise of 50%-75% of the crank shortening amount to start, instead of 100%, you might find it to be the sweet spot.
*(not ideal to fit a smaller chainring due to chain & frame clearances. otherwise I would have gone to 155 or maybe 150)
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cheapondirt
9 months, 3 weeks ago
Thanks for an articulate explanation that isn't a sales pitch. I've filtered out most other short crank content as hype but this was worth the read.
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steelispossiblyreal
9 months, 3 weeks ago
Great read! Don’t forget about Canfield cranks— the OG short crank crew. I’ve been running their 160mm on my Starling Murmur and I have no desire to go back to 170mm. I bet 155mm would even be nice.
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93EXCivic
9 months, 3 weeks ago
I went to 165mm from 175mm cranks and to be honest, I didn't really notice a difference in terms of pedaling. The only differences I noticed where less pedal strikes and having to raise the saddle a touch. The less pedal strikes was awesome. The higher saddle meant I needed a slightly higher handlebar but otherwise adjusted pretty quick.
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Gage Wright
9 months, 3 weeks ago
I wonder if this works for all sizes of riders? I personally ride 165mm now and love it as a good enough pedal and descender. Would shorter legs theoretically benefit more? Could you get Emma to do a comparison article as well?
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Dogl0rd
9 months, 3 weeks ago
Wouldn't longer legs benefit from short cranks as you would have less knee flexion at the top of the stroke?
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TristanC
9 months, 3 weeks ago
Totally anecdotal, but I tried 165mm cranks for a month and they did not work for me; they caused some pain above the knee. I'm 188cm tall, with freakishly long limbs, and am totally happy with 175mm cranks. I am a masher, not a spinner.
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Justin White
9 months, 3 weeks ago
Did you raise your seat a full 20mm? I have found that if you raise that much, the reduced leg flexion can really shift around the loads on your legs. Even just going up 60% of the crank diameter difference, I'm engaging more of my central/inner quad, and much more outer glutes and hamstrings. That inner quad engagement can cause some tension at the top of the knee, so reducing saddle height and thus reducing the time spent nearer to full leg extension might help with that.
I'm a masher as well, when out of the saddle, and I find that short cranks actually let me mash in a bit more of an "L" shape: I can push hard both down and also back, through the bottom, because the other leg is going over the top more easily since it doesn't have to flex as much. Making the switch from over-the-top to mashing again also happens sooner thanks to that less flex. So I gain back much of what is lost from a shorter lever by being able to apply the force for longer.
As you said, with your height and pedaling style, 175 might be your sweet spot, but if you still have the short cranks, I'd suggest giving them a try with less saddle height increase, and the tiniest thought to altering your pedal stroke, and see how you like that.
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Cr4w
9 months, 3 weeks ago
Good news for us all riders are virtually identical. That's why the majority of handlebars have 8' bend and 5' upsweep: all the same wrists joining the bar at the same angle, every one of us. We're so identical I wonder why bikes even come in different sizes.
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Velocipedestrian
9 months, 3 weeks ago
Good news for me, I'm almost exactly the same dimensions as Cam.
Maybe you should track AJ down and get him back to work, more your size, and he always had an interesting perspective.
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Sidney Durant
9 months, 3 weeks ago
6'4" here and although they require a different rpm when climbing, I've been running 145mm cranks for 6 months without issue. For reference the biggest day I've done was 65 miles with 8300 feet of climbing, all on moderately technical singletrack. I left a long comment above with more details, but long story short, short cranks are worth it for me.
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Justin White
9 months, 3 weeks ago
"long story short"
Hahaha, nice one!
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the prophet
9 months, 3 weeks ago
If you do not raise the saddle, and push it backwards as well, then you are losings loads of efficiency and power from the pedal stroke when shortening cranks. Not fair to compare how shorter cranks climb or pedal at all compared to longer cranks if this is not done. And it must feel really weird!
It has been proven many times that short cranks, even with the smaller lever, do not automatically equal a power loss in pedaling. But you have to set the bike up correctly. I find it quite comical that saddle height and setback numbers are so rarely discussed, when they are by far the most important metric in terms of putting power to the ground efficiently and painlessly.
So much concern about bar height at max seat post extension, but no one cares about the knees and hips when pedaling? The roadies have been all over shorter cranks for years now, and the major benefits are not found in descending. That's just an additional perk for mtb only!
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Sidney Durant
9 months, 3 weeks ago
I agree that the saddle needs to be raised for a fair comparison. However I did not find myself needing to move it rearward when going to 145's. That said, I'm always wishing for a steeper seat angle, so maybe that's why I didn't feel the need to bump it back
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Justin White
9 months, 3 weeks ago
You'll get free additional setback with a saddle raise. 20mm added height with a 75 degree (actual) seat tube angle gets you almost 5mm additional set back. Are you saying you need more?
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Cee Cee
9 months, 3 weeks ago
You know what else are carryovers from road racing?--normative saddle height at topout, heels-up pedaling, and the length and location of cleat-mounting channels. Also, ground clearance is science. Plus, a leg is two lengths articulated somewhere in-between
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Justin White
9 months, 3 weeks ago
"is a bit like losing time because the period in which your pedals are in an optimal position to deliver torque is noticeably reduced"
But it all comes out in the wash, because the period in which your pedals are in the least optimal position to deliver torque is also reduced. You kinda mentioned it, but it wasn't presented as as much of a bonus as the opposite was presented as a deficit.
I find that the reduced dead-spot is a much bigger bonus than the defecit of any reduction in absolute instantaneous max torque. If you need corroboration, just look at oval chainrings. They're literally doing the same thing half the time: reducing the "over-the-top" and "through-the-bottom" deadspots. I simply loved oval rings for traction, I think my first impression was a feeling of climbing on a half-flat tire (grip for days) without the squirm. However, I found that oval rings made me want to pedal at a higher cadence because of the reduced dead-spot, but without the equivalent change in max-torque the higher cadence ended up destroying my legs way faster. The reduction in instantaneous max torque becomes a bonus when spinning higher cadences, and a bonus for traction because of the smaller difference between min and max torque.
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Andy Eunson
9 months, 3 weeks ago
I’ve read a few dissertations and tests of crank lengths. They always get a bunch of road riders with lots of experience to test ride different lengths. If I recall correctly they all concluded that riders were most efficient and most comfortable with the crank length they were already riding. That suggests to me that if a person is going to try a different length crank that they have to give the change a fair bit of time before they can come a to a conclusion. If the new length alleviates a knee issue pretty quickly that that’s different.
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Lynx .
9 months, 1 week ago
`OMG, the comments went off fast. Good piece Cam, definitely sparked a good debate/discussion. Very interesting as someone who suffers from hip issues and also not great flexion at the ankles and my now permanent bum knee, so I tried what you suggested and as you said, easily felt. So it should make sense that I move to shorter cranks, but I love my 180mm, they give so much torque and I love to push a harder/taller gear and take advantage of my long legs. I remember about 15 years back I tried 165mmm cranks on my "road" bike for a bit and absolutely hated the loss of power/torque moving from 175mm.
All that being said, now with my knee issue and constant tight hips and ankles compensating for the knee, I may yet look into giving shorter cranks a go, if I can find some 165mm, but I don't know if I could "live" with that loss of power/torque for how I like to ride.
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Justin White
9 months, 1 week ago
I would definitely give them a try on a mountain bike again, especially if your all your leg joints aren't what they used to be. The reduction in flexion from in all parts of the kinetic chain is really nice. I've also distinctly notice more/different muscles being recruited, and it's easier to go from seated to standing with pedals level.
Plus, I can just keep pedaling, since it's so much easier/faster getting over the top of the stroke, where sometimes with a longer crank my more-flexed 44-year-old knees might just give up and not even let me put down that "extra" torque. With shorter cranks, I've actually noticed less of those "almost over the big get-up and now I'm stalled and literally standing on the front pedal but I just can't push any harder to get the few more inches to get the back wheel over the top" event, despite the "loss of power/torque", probably because I'm pedaling full-on more often and more consistently and that keeps the momentum high going into those obstacles.
In other words, I just don't at all notice the reduction in instantaneous torque in trail riding. And I've even been concentrating lately on pushing big gears and having a more sprinter/power-lifter type action as opposed to spin-to-win, even before the crank switch. I think short cranks accommodate this even better because of that quicker over the top action, so you can get back to the power stroke faster and easier. I didn't even change my chainring size to increase cadence, it's just naturally faster & smoother with shorter cranks, thus more chances to put down that power evenly.
To me it's kind of like the people complaining that they can't handle their lowered seat position being 10mm higher, such that they'll suddenly require a longer dropper to accommodate shorter cranks. If 10mm of lower seat height is going to ruin your ride, you must have had a lot of shitty times before droppers got long, and even more before droppers were a thing. And if you always needed exactly 100% of the instantaneous power/torque of a 175mm crank to get over stuff, then you would be ruined by things like: a different cassette with different gear spacing, wet conditions reducing power that can be put to the ground, natural erosion removing material from the low side and making a feature taller, anything that asked for very slightly more power.
In other words: you'll adapt (quickly), and any trade-offs are well worth it, especially if your joints aren't young (or you want to keep them young-feeling). I went from 175 to 170 to 160 on my trail bike, and will never go back to longer if I can help it My hardtail/kid-puller is 170, my all-road/commuter is 172.5, and even going back and forth is fine. And while maybe for a hot minute I felt like I was stuck in the lowest cogs on the first trail ride on the 160s, it turns out I use it for just a handful of seconds more than with the 170s over the course of a whole ride. Of course, when the 51t SLX HG+ cassette arrives with much better/closer low-gear spacing than the 50t GX Eagle, I'll be using the granny cog even less no matter which length cranks I have, so it just goes to show that the whole drivetrain is full of variables, and almost none of them will ruin a ride, but some can make it a bit more comfortable and enjoyable.
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Lynx .
9 months, 1 week ago
Wish that it were that simple, but finding anything but 175mm isn't an easy or cheap option when everything has to be imported in. I've got a total of way too many bikes and all have 175mm cranks, except my 2 personal/main bikes which have 180mm. Really hoping that what Andrew hypothesized happens and there's lots of second hand shorter cranks floating around in a couple years to take advantage of, not really for me, but to have something semi decent/realistic for kids/shorter adult bikes.
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roil
9 months, 1 week ago
Not sure where you're located but SR Suntour's Zeron cranks are 152mm and only $80. I just installed a set on my enduro bike.
https://www.srsuntour.us/products/zeron-1-x
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Eric Schuler
9 months, 3 weeks ago
Great to read more people are hopping on the bandwagon!
I’ve shortened my cranks on my MTB recently to 153mm after a bikefit for the Gravelrig pointed me to 165mm on that one. My kneepain is a thing of the past now. I shortened them myself because the hopes were out of stock and a little pricey and the other options had silly leadtimes. So for the tinkerers out there I can recommend using the old RF Aeffect 175mm as a base - they are solid and cheap and often found second hand. Only thing you need is a standing drill, metal saw, file and the non standard thing already in the shop would be pedaltaps for 25 quid. The cheaper ones did the trick for me with a little patience’s and lots of cutting oil.
Next step is to get a smaller chainring for the steeper climbs. If someone is interested I’ll post a few pictures :)
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fartymarty
9 months, 3 weeks ago
Cam - did you find the shorter cranks affecting turning / grip when you drop the outside foot?
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Justin White
9 months, 3 weeks ago
Not cam, but...
I found that I rather liked how it feels in hard cornering. Being that little bit higher above the bike with the outside foot dropped, and both feet being closer together, means I can more easily get clean bike-body separation.
I've also noticed that the bars have more control authority over the lean, and grip. I think this is from the change to the third class lever of bars (force), outside pedal (load) contact patch (fulcrum): having my outside/lowest foot closer to the bars means it takes less bar movement to make an equivalent change to the lateral position of the outside foot, which is carrying a majority of the load, relative to the contact patch.
In other words: makes 6 & 12 positions feel that much closer to 3 & 9 position regarding finding the edge of traction and living on it.
In other other words, flat corners with a foot out are funner!
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fartymarty
9 months, 3 weeks ago
Interesting - that makes sense re separation. If you moved the feet directly to the BB it should be easier to lean the bike as the lever arm between the cranks is reducing. I am guessing it makes back to back corners at 6/12 easier as you don't need to rotate as far.
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Justin White
9 months, 3 weeks ago
I guess a bit on not rotating as far, same idea as getting over the top faster when pedaling.
However, even better than that might be that pedals-level turns, especially front-foot turns (ie: turning right with left-foot forward) and switch-foot for both direction turns, feel way nicer with a closer stance, so you might not even want to drop the outside foot as often. Keep 'em level, allow the stance to let you move around easier, rip turns both ways no matter which foot is forward.
I've been specifically working on front-foot turns (even before I had that name, thanks Fluidride), and especially switch-footed front-foot turns, for a while now. Partly because apres ride chat, about how everyone likes certain sections more or less because of the majority turn directions, got me thinking about staying symmetrical for adaptability. Partly because I enjoy improving different aspects of myself and my riding. And each time I went down in crank size (175, 170, 160), all turns (including outside pedal down, but especially switch-foot front-foot turns) became smoother and less unnatural feeling.
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fartymarty
9 months, 3 weeks ago
I've been working on switch foot turns (outside foot back) altho it's still a worknin ptogress and doesn’t happen as naturally as I would like.
Switch footed front-foot turns sound like something I need to try.
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Cam McRae
9 months, 2 weeks ago
I corner with my left foot forward/cranks close to flat almost exclusively and I didn't notice any negatives at all.
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