Talking to a couple of the guys from Shimano at Interbike last year, I asked what they thought the best part of the XTR group was. Expecting to hear about slick 10 speed shifting or life-changing double cranksets, I was surprised when they both said the same thing: the brakes.
“Of all the things that people come back excited about, it’s the new brakes” said one.
“Yeah, they’re badass” said the other.
A month later, when my own kit arrived, I had to agree. The M988 “Trail” brakes are really the XTR group’s standout. Nearly ten months later, I’m still wringing life out of my 9s gear, spinning a triple- and rocking the XTR brakes. Hit the jump to find out why…
2012 marked a number of changes in Shimano’s flagship group. Acknowledging the growing number of riders who are looking for high end equipment oriented more towards all-mountain or trail use, they split parts of the M980 XTR group into Race and Trail sub-groups. In the case of the BL-M988 levers, this means that the company’s ServoWave variable leverage mechanism is used in addition to the BL-M985 Race model’s split clamp, stubby dimpled lever, and in-line reservoir. The BR-M988 calipers get heat-dissipating finned pads in addition added to the BR-M985’s insulating pistons and one-piece forged body. The levers are also 1mm wider and dimpled for feel. All of this adds up to a meager 25g per wheel weight premium over the Race version.
Despite looking a bit bulkier (to my eyes) than the previous generation’s radial master cylinder, the inline cylinder on the revised XTR levers is said to be lighter and easier to bleed. The hinged clamp is welcome to those of us who compulsively move brakes between bikes- but will be less of a benefit to the fit-and-forget crowd. Interestingly, the hinge won’t open completely without poking a spring pin through a small hole- this is to keep the lever in place (and out of the front wheel) in the event of a bolt failure. 
On-trail reach adjustment is available by way of a chunky knob, and lever free stroke is adjusted via a Phillips screw head.
Setup was easy, with the rotor allowed plenty of space thanks to the levers’ Servo Wave feature. Servo Wave, first used on cantilever brakes, is a mechanism that varies the brakes’ leverage as the levers go through their stroke. To start, the pads move quickly to cover the above-average amount of space between the pads and rotor, after which the leverage ratio increases to provide one-finger braking power as impressive as anything I’ve felt this side of a downhill brake. Though it does mean more moving parts, the brass follower feels as smooth now as it did when new and there is no real discernible transition between ratios. The 180mm front and 160mm rear adapters have been visibly lightened over previous Shimano efforts, with the front post mount adapter (shown above) changing to the bolt-through type that Formula have used for some time. 
The hardware now uses 4mm heads- probably lighter and only a tiny bit frustrating after automatically reaching for a 5mm Allen key.
Since their arrival, I’ve been putting off reviewing the XTR brakes because… nothing exciting has happened. That said, the last thing most people want in brakes is excitement. Used with standard steel rotors (as opposed to Shimano’s new steel-aluminum-steel sandwich Ice Tech rotors) from several companies, the M988s have provided consistent, fade-free one-finger braking. I’m not much of a brake dragger, but Shimano’s effort to keep the XTR brake system cool seem to have paid off- and should go some way to quieting mineral oil doubters and comforting big mountain descenders. The brakes have been quiet everywhere- on every rotor in all conditions- and the big pad clearance has kept them from rubbing, even on wobbly rotors. Modulation is fantastic- though they have a somewhat softer lever feel than many competitors’, the XTRs’ power is easy to control they’re far from mushy.
And now for the warts. The first I encountered was on installation, when I felt the lever mounting bolt- with its flat underside- grinding against the clamp- which has a spherical depression. It sounds picky, but this just seemed cheap on a $270/wheel (plus rotor) brakeset. While the new lever- especially when paired with the ServoWave mechanism- doesn’t need a whole lot of length to be effective, it could be a smidge longer for those of us who prefer middle finger braking. 
As it stands, I’ve got my levers rammed up against the end of my grips. It seems to me that the free stroke adjuster doesn’t allow the rider to dial enough out. Though it could eat in to the pad clearance, the XTRs do lack the immediacy of Formula’s RXs. Finally, the trigger lever of my previous-generation (M970) XTR shift levers can occasionally hang up on the lever’s clamp. Not a huge deal while riding (I usually push the trigger with my thumb), but still…
The M988 Trail brakes come in at about 235g (front, no rotor). Figure on another 120g (and $60) for a Centerlock or 6-bolt rotor and hardware and you’ve got a brake that comes in very close to Avid’s $245 (with rotor) X0. All together, my set was almost identical to that of a Formula RX pair that I had in the workshop- but a full 100g (or 1/4lb) heavier than Formula’s race-oriented R1.
The XTRs’ price isn’t cheap- but their quality is clear and overall performance has been excellent- and in my opinion the highlight of the M980 group. Seeing as these brakes were a personal purchase, would I do it again? My head tells me that there are a number of very good brakes on the market that do much the same, at the same weight, for significantly less money. My heart reminds me that these are among the very few brakes that I’ve ridden that haven’t rubbed or squealed once. And that they’re shiny. It’s always been difficult to justify the XTR price premium, but my experience suggests that, as the miles pile on, XTR parts’ performance continually pulls further and further away from the competition. Despite a handful of minor complaints, the XTRs have become my favorite trail brake- if your budget will stretch to them, you’ll be happy. I, for one, can’t help but want another set.
marc
TYLER’S TWO CENTS
I attended Shimano’s new XTR launch last year. We were able to test the equipment on and around the Downieville trails, including some screaming fast and technical descents. The full write up, including pics of these brakes on the scale, is here and here.
Since then, I’ve moved the brakes around on several bikes with both 26″ and 29er wheels. Here’s my only two-part complaint: Because the XTR level Ice Tech rotors aren’t available in 6-bolt yet (only CenterLock), I ran them with Ashima’s Air Rotor in 180/160mm front/rear but they squealed horrendously. Same bike with Avid X0 brakes and the Ashima rotors is quiet. Shimano, please make XTR level Ice Tech rotors in 6-bolt. It’s worth mentioning that they do have XT level 6-bolt Ice Tech rotors either available now or coming very soon.
I also used both the organic and semi-metallic pads, and both work phenomenally well. I felt the latter had a bit more immediate bite, and they’re what were used with the Ashima rotors.
Other than that, I agree with Marc’s performance evaluation. The brakes are simply amazing. I’m a bit taller and bigger than Marc, and any issue with the levers being a bit short are slightly exaggerated for me, but over the last two years I’ve slowly transitioned from being a middle finger braker to a pointer finger, so his concern isn’t much of an issue for me. If you like braking with your middle finger, it might be a bit of a stretch, particularly for those with big paws. I didn’t notice any issues with the shift levers interfering with the brake lever assembly.
