02 December 2008

bikefix Exclusive Review: Shimano XTR disc brakes

When considering disc brakes, it never ceases to amaze me how many people overlook Shimano's offerings. Luddites turn to Avid mechanicals when Deore hydraulics run nearly the same money (when brake levers and cables are considered). Similarly, folks building up higher-end rigs often completely overlook the company's XTR discs. I don't quite understand why- of all of the mountain bike disc brakes that I've had the opportunity to ride, own and work on, Shimano's have required the least maintenance by far. When you factor in their reasonable prices and weights, non-carcinogenic fluid (yes, DOT fluid causes cancer), superb lever shape and modulation, it's pretty surprising that they're not everywhere.

Of course, it's all too easy to rave about most companies' top of the range equipment. After all, its typically that company's lightest/strongest/sexiest effort. For my money, Shimano's XT hydraulics are certainly some of the best on the market. That said, when I was building up a new XC race bike a couple of winters ago, I had the time and energy to piece together some very nice parts from all over the Interweb. At the time, Shimano's M975 XTR group had just been released and the brake levers were a revelation. Replacing a somewhat lumpy Dual Control unit were some of the sexiest standalone brake levers I'd ever seen. The M975 lever body is a single forged piece, with the reservoir located (Magura-style) between the lever pivot and the bar. The levers had Shimano's trademark dogleg shape (perfect for middle finger braking out at the hook) and were bead blasted for improved grip. A race-oriented group, the XTRs forgo the XTs' adjustable bite point and the lever reach is adjusted via an (easily accessible) Allen head screw. Given my experience (and pleasure) with previous generations of XT discs, I was sold.

For calipers, I was able to locate a pair of the previous generation M970s. While not the latest generation, the price was certainly right. Like the levers, both old and new XTR calipers are a single-piece forging, with minimal additional machining to disturb the metal's grain structure. While many brakes (including lower-level Shimanos) have gone to post-type calipers and adapters for ease of manufacturing (it's the same caliper front and rear) and setup, Shimano's lightest have stuck with IS mounting and wishbone-style spacers. Eliminating an adapter and two bolts from each wheel not only reduces the chances of something going wrong, it also saves something like 60g at each end, which helps keep the M975 system weight to a respectable (if not earth shattering) 360g. Seeing as mine were going on a 29er, I did use an adapter to allow for a 180mm front rotor- the bigger wheels really do seem to benefit from the added stopping power. M975 brake sets are sold by the piece or as a pre-bled set with either centerlock or IS 6-bolt rotors.

Of all of the brakes I've ridden, Shimanos provide the best modulation at the lever. The XTRs are no exception. If you're a fan of more wooden feeling brakes (say, Hayes), the first showroom squeeze will be a bit of a turn-off. It's not that the XTRs lack power (they don't- though others do have more), but it's that it comes on progressively and controllably. This makes feathering the brakes at the edge of your tires' traction limit much easier and serves to maximize that power. It also minimizes unintended skidding. Remember, skids are for kids- not for your local trails. Besides, you'll stop faster if with the wheels just shy of locking up (think ABS in the car).

Over two years of hard use, my only maintenance to the XTRs has been pad replacement and to add a bit of mineral oil to the rear brake's reservoir. Power has been more than adequate for hauling a big-wheeled bike down from speed and the feel has been fantastic. While some play has developed in the levers, they've never been as rattle-y as other companies' tend to be out of the box and less than my Formula Oros have developed over the same period of time. Best of all? They've still got a year left on the three year warranty.

If you're looking to spend $350 or so per wheel on a set of lightweight brakes, there are a lot of attractive options. While not the lightest available, Shimano's XTRs are some of (if not the) the best built brakes around. They're pretty readily available for far, far less-, which makes them also one of the best deals around.

marc

www.shimano.com

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