The secret story behind the most advanced MTB brake ever

14 May 2020

The ‘R’ in XTR stands for ‘Race’ - that is very important. The lineage of Shimano’s top flight competition-orientated groupset goes back as far as 1992 and with each iteration has come an ever-tighter focus on pushing boundaries of weight and performance. Although it has only been around for seven years, the Enduro World Series has itself pushed bike technology further than any race series before it.

The latest M9100 series of XTR was Shimano’s response to the new ceiling that enduro racing was establishing. But it wasn’t straight forward. This is the inside story of how one brake was designed to be the best ever and dictated that a company the size of Shimano completely rethought how it did things. 

The finished, production version of the XTR M9100 brake in action at 2019's Zermatt round. Pic: Kike Abelleira

It started, as an alarming amount of good things in the bike industry do, in the pits. Shimano technicians observed that more and more often EWS racers were requesting not only their top-of-the-range downhill brake, SAINT, but also their largest 203mm rotors. With EWS stages including the likes of Whistler’s Top Of The World and Lo Barnachea’s monstrous Parvaso it was clear that power and heat dissipation were top of the pro’s lists when it came to brake attributes.

With SAINT, Shimano knew that they could already engineer sector-leading stopping power but they also knew that when it came to enduro racing and riding long, fast, technical trails that feel and consistency were of equal importance. Feel in particular is very different from power and is harder to define which in turn makes it tougher to engineer.

Big speeds equals big stops - Jesse Melamed powering through Madeiran dust in 2019.

The company’s patented SERVOWAVE action gave them a head start. SERVOWAVE is best explained right back at the basics of what a brake needs to do; it has to convert the relatively long lever travel into a smaller but more powerful piston movement in the caliper. Where SERVOWAVE is clever is that it changes the rate at which this happens. Initially, a lot of brake fluid is moved with lower pressure to move the pistons quickly before the leverage ratio changes and they then move slower but with more power towards the end of their stroke. The result is a brake which feels sensitive at the start of its lever stroke only to then ramp up dramatically in power when a rider really needs it to. 

The SAINT brake was designed for downhill racers who require a lot of speed to be shed very quickly and often extremely aggressively. Therefore, the SERVOWAVE’s ramp up is tuned to allow a rider to hit that wall of braking power very early on in the lever stroke. What the engineers who were charged with developing the new XTR had to establish was how much power enduro racers now needed and how much ramp up was required to achieve the all-important feel. There are of course many other factors which could affect things in the feel department too right down to calliper material thickness and piston size. Drawing up the right combination of all of them was going to be a tall order. 

Shimano engineers and riders prepare to embark on a day of testing. Pic: Sterling Lorence/Shimano

Shimano, famed for their extensive research and development practices, realised that developing the new brake was going to require them to change their time-honoured in-house testing approach. The enduro pro’s were pushing things further than their test pilots would; a new standard was needed and so they set about the most detailed and thorough set of testing that they’d ever embarked upon.  

They began by surveying  200 of what they classed as ‘key athletes’ alongside entering into detailed talks with some of their biggest names in order to work out what the new brake needed to be and, critically, what it needed to feel like.

The engineers realised that for many the outright power of a SAINT brake on a lighter weight bike was too much and often tricky to modulate. The flip-side was that with some enduro stages increasingly resembling top-level downhill tracks and bike and tyre tech progressing rapidly, that that power was often still needed.

The test riders ran Saint brakes as a benchmark for the stopping power needed. Pic: Sterling Lorence/Shimano 

Work needed to be done and so a secret test program was put together which saw Shimano engineers from around the world meet at a test camp with a select group of riders including Jesse Melamed and Thomas Vanderham. Engineers from Japan were flown in hand carrying several prototype versions of what they proposed to be the next XTR brakes complete with a host of different features and tunes. 

Rocky Mountain Race Face's Jesse Melamed was on hand to give feedback throughout the testing process. Pic: Sterling Lorence/Shimano

Melamed's pace and consistency were a big help in replicating the demands of an EWS stage. Pic: Sterling Lorence/Shimano

Multiple runs of a lengthy, severe trail on bikes familiar to the testers were banged out over several days. At the end of each pass, riders delivered detailed feedback whilst the engineers set about recording their data and swapping between prototype brakes.

One of the prototype calipers gets mounted up. Pic: Sterling Lorence/Shimano

These sessions were interspersed with similar runs of longer, mellower trails to help to make sure that the brakes were being tested in as broad a field as possible to match the varied conditions of an EWS season and the wider riding environment which modern bikes are exposed to.

Freeride pioneer Thomas Vanderham, pinning it!  Pic: Sterling Lorence/Shimano

Melamed riding the ragged edge. Pic: Sterling Lorence/Shimano

The amount of first-hand feedback the riders were asked to provide was extensive. Pic: Sterling Lorence/Shimano

The testing was extensive and at the end of the camp each rider was asked to evaluate every detail of the prototypes. The engineers had no idea what would come back - production and the fruits of all their labours hung in the balance. When all the results were tallied, every tester opted for the same prototype! The engineers returned to Japan to begin converting the favoured prototype into a production-ready brake, happy that they now had the rider feedback which directed them to the all-important balance of feel and power.  

Melamed drops in. The test loops varied in terms of severity and length. Pic: Sterling Lorence/Shimano 

Feel is of course just one of the main areas XTR has been improved in. When you drill down into the numbers, just about any parameter of how you judge a MTB brake has been bested. Lever stiffness has been bolstered thanks to moving the clamp in board and adding an additional brace underneath the lever itself.

Shimano's Joe Lawwill was also involved in helping to put the prototypes through their paces. Pic: Sterling Lorence/Shimano 

The new ICE TECHNOLOGY FREEZA rotors use a special heat-dissipating paint on the exposed aluminium layer that can see heavy braking temps reduced by as much as 150 degrees celsius over a standard rotor. Longtime fans of Shimano’s equipment will of course know that the trickle-down effect of the tricked-out new XTR is good news for everyone as many of its technologies inevitably trickle down through to XT and SLX groupsets.

Find out just how much of the impressive XTR tech made it into the all-new Deore groupset, here

Shimano engineers waiting at the finish to swoop in and take their measurements. Pic: Sterling Lorence/Shimano

In the world of mountain bike technology, the marketing spiel forever cites bold new boundaries and higher ceilings but what Shimano have achieved with the latest XTR is undeniably seriously impressive. The headlines swirled around M9100’s HYPERGLIDE+ 12-speed shifting but the sheer amount of work that has gone into producing a brake which isn’t simply ‘lighter than all the others’ but performs at a level the off-road community has never experienced before is something different. It’s something that can genuinely allow racers, of all abilities, to push harder than ever where it matters - between the tapes.