Pros: Zen-like lever feel, reliable all-weather braking, constant and steady power application.
Cons: Possibly the most expensive mountain disc-brake system, pain-in-the-brain installation, very difficult to bleed brake-lines.
As the next part of my 2003 Shimano XTR component review series, Ive decided to tackle the BR-M965 Hydraulic Disc Brake system. To save space Ill shorten the product name to M965 HD for the rest of this review.
----- Introduction -----.
After the couple years of riding and racing on Avid BB Mechanical Disc brakes, Ive become used to the performance and reliability of cable actuated disc brakes. When I decided to upgrade to full XTR on my Specialized S-works Epic, I couldnt bear to use the V-Brake system. It was with a heavy heart and much trepidation I opted to go the hydraulic disc route. With the new XTR Dual Control shift/brake levers, you could run Avid disc brakes by deleting the V-Brake system and using the M960 V-Brake levers. I decided to go for the M965 Disc levers instead and take my first baby steps into the world of hydraulic brakes.
For quite some time Ive heard great things from riders using hydraulic brakes, but I never thought Id convert to them. The feel of hydraulic systems is much like a car, or even more like a quality hydraulic motorcycle brake system. They resist fading better than cable discs, they are easy to modulate brake pressure right to the edge of tire lockup, and are generally more powerful due to larger pad size and dual piston caliper design. However, as the classic monster ballad says; Every rose has its thorn. Hydraulic discs are no exception, and the two biggest problems are air in the hydraulic fluid and lack of caliper adjustability. Ill get to both those problems later in my review.
----- Okay, Now I Attempt To Install Them -----
Ladiieeeees and Gentlemen, let the circus begin! After working on all my friends bikes, upgrading several drivetrains with new components, and building 3 bikes from scratch I consider myself a pretty decent home bike mechanic. I can tune shifters in less than five minutes and change a tire or tube in under two minutes all this was useless when it comes to installing the M965 HD brake system. I had read enough reviews of this system to know it either works great or is a complete disaster. The biggest problem most users have is attempting to install themselves and not following Shimanos instructions.
I knew all this, and still I goofed up royally. Installing the hardware was no big deal, both shift/brake pods and calipers installed without any fuss. A couple notes on the caliper installation:
1: The allen-head caliper mounting bolts WILL crack the paint finish on your bike if you dont use a washer under the bolt head. As they become tighter the bolt head grabs the paint and pops it right off your frame.
2: These calipers dont have any adjustments for evenly spacing the distance between each brake pad. The M965 HD set comes with several fork shaped shims that you must install between the frame and the caliper body before you tighten the caliper bolts all the way. I needed two shims on the lower bolts and one shim for the upper bolts to space the caliper correctly.
With the kit I purchased both brake lines were pre-cut for almost exactly the right length and pre-filled with Shimano fluid. The good news is you can cut these brake lines to the right length to fit your bike, but be careful to cut the line using Shimanos instructions. Unlike other brands such as Hayes and Magura which use automotive spec DOT brake fluid, Shimano uses mineral oil in their M965 HD system. Not only is this easier to handle but its much less corrosive and damaging to painted surfaces. This fluid caused the first big problem when I attempted to bleed the air from my brake lines. I proceeded to purchase a 20oz bottle of premium mineral oil from my local Walgreens drugstore. In my defense I did read the large instruction book that came with the brake system and it didnt mention any specific fluid type. After trying to bleed the system from the brake lever reservoir down to the caliper I found the brakes were spongier than ever, and the levers almost touched the handlebar before actuating the caliper.
After stopping by my local bike shop and querying the friendly service tech he informed me there was a reason the Shimano fluid was a bright red instead of clear. Shimano fluid has detergents, flow enhancers, heat resistant additives, and a couple other chemical treatments. In other words I had to use Shimano fluid, and Id wasted all the original fluid that my lines had been filled with. If you mix Shimano fluid with standard mineral oil you have to toss it out, since the cross contamination ruins the Shimano fluid.
Then is when I discovered Shimano fluid is $15 for a 50-milliliter bottle. 50ml is a VERY small amount of fluid, and I need 1.5 bottles just to refill and bleed my system. Oh yeah, and you cant bleed this system effectively without the Shimano bleed kit which is another $60 if you can even locate one. Apparently Shimano doesnt like to sell this bleed kit to customers, and would rather sell only to shops. Luckily I was friends with this shop so I was able to borrow the bleed kit for the night. This kit is completely necessary, and makes bleeding the lines a no-brainer project. The Shimano kit is $50 and includes the items below:
50ml of fluid
Brake reservoir clamp with fluid overflow bottle
All necessary hoses
Dont ignore Shimanos recommendation to remove your brake pads when bleeding the system. They give you yellow spacer blocks to insert in place of the pads. If ANY mineral oil gets onto the pad surface it soaks in and is impossible to get out. The pads will NOT stop well at all, and will glaze over very quickly as the mineral oil in the pad compound burns off. I was sure I could bleed both brakes without spilling any fluid, but I didnt count on a hose popping off the bleed screw. Another $25 wasted on a new set of pads I shouldnt have needed. Once you actually get the system bled effectively youll find the lever only moves about ? of an inch towards the bar on full brake application.
----- Using The M965 On The Trail -----
The biggest difference between cable and hydraulic disc brakes is the lever feeling. Cable systems feel very hard right away, while hydraulic levers feel soft initially and progressively become stiffer as you apply more pressure. This is hard to explain until youve experienced it yourself, but what youll find is you can apply hard pressure right to the point of tire lockup and hold it there. Cable systems are much harder to predict tire lockup, and you can find yourself with an unexpected loss of traction as you tire slides. While riding fast singletrack or downhill sections I find myself much more in tune with my bike, and able to pick up the flow of the trail better. After you understand the lever feel of the M965 you can work the corners and maintain your speed much better than with V-Brakes, and slightly better than cable disc systems.
Hydraulic discs also offer more stopping power, which is great if you ride downhill a lot or are just a heavy rider. Unlike cable systems, the M965 has a double-acting dual piston design. This mean even pressure is exerted on both pads simultaneously. The pads themselves are rectangular and elongated for more surface area. Two different brake pad compounds are available from Shimano, with the softer natured resin pads coming with each new brake set. Resin pads have the lowest noise level and are the easiest to modulate braking power. Metal matrix pads are the most fade resistant and most powerful, but have a tendency to feel a bit grabby.
Like all its disc brake brethren the M965 is naturally good in nasty conditions where mud and water are present. The cross-drilled rotor design is excellent at keeping them cool, and also keeping them clean. Shimanos Center-Lock rotor system is a great idea, combining the benefits of spline drive and single-nut installation in an easy to use package. Shimano implemented a brilliant idea seldom seen in bike parts, and uses the XT/XTR splined cassette tool to remove and install brake rotors. This allows you to have one tool to work on multiple parts of your bike, I only wish more components were tool-compatible.
----- Bottom Line -----.
While Im completely stoked about my XTR Disc system, I have to see it in a subjective light. As an upgrade I can't really recommend them for the average mountain bike enthusiast. Once you combine installation difficulty, fluid cost and availability, maintenance, tuning, and the somewhat marginal superiority over cable disc systems, the overall package value is debatable to say the least. Id estimate the upgrade and/or initial purchase price to be between $550 and $800 for this system. The brake system itself isnt too bad, and a front and rear set will lighten you of $280. However, you also need the XTR M965 Dual Control levers, and at least one bottle of fluid to bleed your new system. Not to mention you'll need the Shimano specific splined hubs for the rotors to work. You can use XT or XTR hubs, but you'll still have to buy new rims or have new hubs installed in your existing wheels.
If youre good at working on your bike and want to try installing these yourself then I'd give them a big thumbs up. If you're going to rely on a bike shop to install and tune them I wouldn't be so quick to jump on the bandwagon. As the head shop mechanic admitted to me, he's only had a 60% success rate with the XTR Disc brake system. One set he couldn't get to stop squealing no matter what he tried. Another set he couldn't get the levers to feel firm after multiple bleeds and a caliper change.
I'm happy with my brakes, but they work great and so far have held up very well. If I had shrieking pads or mushy levers I wouldn't be near as satisfied. I'd like to give these brakes four stars for my personal experience, but as a whole including value and user friendliness they are much closer to three stars hence my rating.
Thanks for reading, and feel free to comment!
Shimano XTR WH-M965 Wheelset
Shimano XTR M965 Dual Control Shifters
Shimano XTR FC-M960 Crankset
Shimano XTR RD-M953 Derailleur
Avid Ball Bearing Disc Brake