Shimano XT M8100 four-piston brakes on test – Where there is lots of light, there are also shadows
Last year, the design and features of Shimano’s flagship XTR brakes trickled down to their XT and SLX range. The differences between the two models are minor, so we opted to use the XT M8100 four-piston version for our long-term review. Could it convince our heavyweight tester, Felix?
It is extremely difficult to stay abreast of Shimano’s model numbers and abbreviations. But, the latest models of their fantastic looking XTR, XT and SLX four-piston brakes have been around for almost a year. Our 92 kg chief of testing, Felix has putting the mid-range Shimano XT M8100 four-piston brakes to the test on his downhill-oriented NICOLAI G1, paried with 203 mm rotors front and rear. The biggest innovations of Shimano’s new generation brakes are in the brake levers. They don’t only feature a wide clamp, but they’re supported against the handlebar at a second point. That way the levers should be even stiffer and feel more direct when pulling the brakes. As usual, Shimano rely on their proprietary Servo Wave technology where the brake pads move quicker at the beginning of the stroke. The leverage ratio changes over the course of the stroke and the brakes become more powerful towards the end. This is how Shimano create the brake feel they’re known for, with the XT M8100 biting very quickly but still giving you lots of modulation. The generous, tool-free lever reach adjustment is another feature we’ve come to love. It’s quite the opposite with the bite point adjustment, which requires an antiquated screwdriver and only has a minimal effect on the actual bite point.
The brake levers are paired with beautiful four-piston calipers. The newly designed cooling fins of the ICE-TECH brake pads simply look great, but they rattle loudly on rough terrain which gets very annoying. It often helps just bending the pad springs open a little further and reinserting the pads. If that doesn’t do the trick, the problem can be solved with a bit of Velcro between the calliper and the cooling fins. Despite the initial rattling, Felix continues to use the ICE-TECH pads. He’s opted for organic pads up front for even more bite, and sintered versions on the back for better heat resistance.
The ICE-TECH rotors with the oversized cooling surfaces are able to handle continuous braking really well, but they’re only compatible with Centerlock hubs. If you’re relying on 6-bolt hubs, the best alternative is to use the simpler SM-RT86 rotors.
The large cooling fins tend to rattle on the brake calliper. If bending the pad springs open doesn’t help, you can either use Velcro or pads without cooling fins.
In theory, this screw can be used to adjust the bite point. In practice, we only used the screw to bleed the brakes and push back the pistons. On the trail, we always screw it all the way in.
We were particularly impressed with the power of the Shimano XT M8100 brakes, which is consistent, doesn’t require a lot of manual force and available early on in the stroke. Even on long descents of 1,000 meters or more, Felix couldn’t get the brakes to fade despite his 93 kg weight. The light ICE-TECH rotors with the aluminium core and generous cooling surfaces certainly play a part in this. But even with the latest generation brakes, there is one recurring problem that Shimano havn’t got under control: the bite point of the Shimano XT M8100 brakes wanders significantly, especially on rough trails. When braking, the brakes grab just as you want them to, but the bite point can be far away from the lever before hitting one corner only to have you almost pull the levers against the bars as you approach the next steep section. Our tester Felix got the wandering bite point under control with regular bleeding and overfilling the reservoir – at least it’s quick and easy with the funnel method – but it was never completely gone. However, if you overfill the reservoir, you have to be careful when changing the pads so that the seals on the brake lever aren’t subjected to excessive forces when pushing the pistons back in. We’d advise attaching the bleeding funnel to the lever and/or to close the bite point adjustment completely. So, it’s good for something after all.
With the latest generation XT four-piston brakes, Shimano have not only hit the mark in terms of looks. The XT M8100 is also one of the most powerful and reliable brakes on the market. Love it or hate it. The former applies to Shimano’s typical lever feel, which our tester Felix and many others appreciate. Hating it applies to the constantly wandering bite point!
Tops
- very reliable and heat-resistant
- powerful yet easy to modulate
- super easy bleeding
Flops
- wandering bite point
- brake pads can rattle
- ICE-TECH rotors are center lock only
Tester Felix
Duration 10 Monate
Price approx. € 200 (Brakes), approx. € 65 (203 mm disc)
Weight 397 g (brake with 203 mm rotor)
For more info bike.shimano.com