Shimano SLX Four-Piston Brake Review

In the first part of my Shimano SLX M7100 group review I dove into the drivetrain and attempted to answer the question; can SLX provide the performance of more expensive Shimano gear? With a minor change, I found the difference between the SLX M7100 and XT M8100 drivetrains negligible on the trail, making SLX a great option for riders hoping to save a few bucks. My experience with the new SLX 4-piston brakes has been similar. A small change has provided me with adequate power and a reliable set of brakes. They’ve punched above their weight in the six months I’ve had them and are capable of stopping the bike in situations typically reserved for aggressive downhill brakes.

Features:

• Two and four-piston options available
  • Four-piston tested
• Reach adjust lever
• Servo Wave lever
• New I-Spec EV Clamp Band
• Finned resin (stock) and Metallic pad options
  • Non-finned resin and metallic pad options
• Weight: 917g
  • Front – 469g (w/ full 1,000mm brake line and 203mm rotor)
  • Rear – 448g (w/ full 1,700mm brake line and 180mm rotor)
• MSRP: 179.99 USD / 199 CAD w/o rotors

SLX M7100 Four-Piston Brakes

The SLX M7100 brakes are available with two or four-piston calipers. Shimano shipped the four-piston test brakes with their finned resin pad but there is also a non-finned resin option.There are finned and non-finned metallic options as well. The brake design is based on the new XTR stoppers and features a similar appearance. At the lever, the SLX and XT levers share architecture but differ slightly to the XTR. Setup was straightforward and thanks to the I-Spec EV adapter, the SLX and later XT shifters each mounted seamlessly to the brake lever assembly.

With the lines cut to length, I bled the setup using my preferred gravity method. A visible difference between the SLX master cylinder and the more expensive XT and XTR is the absence of the free stroke adjuster screw. This feature's seldom used by the majority of riders and most won't miss it on the SLX lever.

I have however found the free stroke screw can be helpful during a bleed. Winding it out helps prevent air from getting caught around it and a post-bleed free stroke adjustment results in changes at the lever. Without it, I found extra caution and more time were required to get a nice bleed. With the lever detached from the handlebar, rotating and tilting it allowed me to remove more air from the system. I also had to utilize the piston-cheat method to get the lever throw I prefer, topping up the fluid before finishing the bleed. Once the brakes were sealed up and the lever mounted, everything felt great and this set didn’t change throughout testing. They never required another bleed and the brakes saw everything from 0ºC to 30ºC weather.

Looking for Trouble

Until late July, the only brakes I’d ridden in 2020 were four-piston SLX. They came fitted to the 2020 Norco Sight I reviewed and the test set was mounted to my G1. On both bikes the brakes were excellent but I noticed a difference early on. Actually, there were two but I’ll start with the noise… Immediately on my G1 a new rattle was present and based on previous experience with the finned Shimano pads, I had a hunch what it was. I dealt with it for a few rides, convinced I'd try the soft velcro trick seen on some World Cup DH bikes. But then the Sight arrived with a slightly different pad set up. It had non-finned pads and on the trail the brakes were quiet. Switching the pads over to my G1 for a couple of rides confirmed it and a fin free set were purchased to continue the review.

The second thing I noticed was the braking characteristics of the pads. When the brakes were first bedded in on my G1 everything was fresh, with Shimano also including their Ice Tech rotors. But the bite I'm accustomed to from Shimano wasn’t there. Once again I confirmed it using the Sight, which came with fin-free metallic pads (kudos to Norco). The metallic pads brought the brakes to life in all conditions. Initial bite increased dramatically as did full power.

Most of the review period was spent on the metallic non-finned pads. Not everyone will be annoyed by the fin rattle and some riders will benefit from the more gentle attitude of the resin material. But for the most stopping power in a rattle-free package, a set of fin-free metallic pads is a must. Riders who find the Shimano brakes too “on-off” but otherwise enjoy the system could try the resin options. Other than less bite and power, I didn’t experience any other problems with the resin pads.

With the metallic pads, there was a brief adjustment period to the bite of the brakes. Combined with their lever feel, initial contact with metallic pads is quite aggressive but it was welcome once I adjusted to it, providing quick stopping power at times of need. More power is added easily and managed well through the feel of the Servo Wave lever. I can’t say I noticed the added stiffness of the new lever design but it’s also been a while since I rode the previous generation. Nevertheless, the general feel is similar to the previous-gen. XT and XTR models.

The brakes on my G1 were subject to the long steep descents of Pemberton, Whistler Bike Park and my local trails in Squamish, B.C. I’ve not had a single brake make it through a six month test period without some change in feel, until now. That includes previous generations of DH brakes. The four-piston SLX brakes punch well above their class. I did experience some noise when things heated up, with the rotor skimming the pads more until things cooled back down. But with the brakes otherwise continuing to perform as expected, with plenty of power on tap and no change in feel, it wasn’t a concern.

While the experience on my G1 was excellent, the set on the Norco Sight differed with some very mild wander and pump at different times in Maydena, Tasmania. The Norco mechanic who built the test bike informed me that his bleed process is one of a “fluid pusher.” While his bleed procedure differed to my gravity bleed, I'm not convinced this was the cause and believe it more likely comes down to the multiple flights the bike took along with a lack of care between. It was really minor and carefully focusing on the problem was needed to confirm it. This happened after multiple days of long, steep laps on Maydena’s finest, and multiple partial teardowns to box up for flying.

With World Cup Downhill athletes like Loris Vergier not shy to use XTR and the SLX/XT brakes based on that model, I guess the available power shouldn’t be a surprise. Without any time on the new XTR brakes, I can’t comment on a direct comparison. However, I can confidently say that the SLX brakes provide adequate stopping power in situations I previously would have pined for a full-blown downhill brake.

I found the shape of the lever blade among my favourites to date. Shimano's lever blade design doesn’t feature any boxy pieces or sharp edges; it's slender but feels adequately stiff, providing a positive feel when jumping on the anchors. The SLX lever doesn’t feature the dimples of the XT and while they feel nice, it’s not worthy of the additional cost. At the end of the lever, the hook comfortably hugs the finger and the power of the brakes means there’s no need to use two. XTR lever blades feel nicer to touch but again, I wouldn't pay the extra.

Verdict

As I found with the new SLX drivetrain, these brakes make it hard to justify the extra money for XT or XTR. They performed sensationally in full-on DH situations, whether in the Whistler or Maydena bike parks or on long, steep trails accessible in Pemberton and Squamish. After a solid bleed, they rode trouble-free until removed more than 600kms later. For 175 USD and ~10 grams more weight than the XT brakes, SLX is a great option for even the most serious riders.

More info on the Shimano SLX M7100 trail brakes is available on the Shimano website.