In 2018, the team is once again running the new top-of-the line bike from KTM, the Revelator Prestige. The bike is totally rad, but that’s not what this post is about. This post is about the brakes on the bikes. The Revelator Prestige frame has direct mount brakes. As I was installing our new jet black TRP brakes on my bike, I thought now would be a good time to share what I’ve learned from building up and riding a bike with direct mount brakes.
I’ll start with a bit of background. A traditional brake calliper attaches to a single central bolt at the center of the fork right above the crown via a hex bolt. You attach and tighten the brake from behind the fork. This is the brake that you’ve seen on road bikes for years. When installed correctly, it self centers and works just fine.
Direct mount brakes are different system for rim braking. A direct mount brake attaches to the frame with two built-in fittings, one for each arm of the caliper. This places the brake closer to the frame and increases the rigidity of the system, leading to better braking power and modulation. It also gives a larger clearance in between the arms of the brake, which gives you more space to run big tires and wide rims. This is super important in the age of #groad #gravelgrinder #monstercrossbikes with wide carbon wheels and high volume tires (28c or greater).
Direct mount brakes also allow frame builders to position the brake in different locations. Why do they want the brake in a different location? Because the normal seat stay position for the brake is one of the most flexible areas on a bike. The chain stays right behind the bottom bracket are a much stronger, and more aerodynamic, position. Mounting the brake on a stronger part of the frame gets you a better performing brake. That’s what KTM has chosen to do on our new bikes, and I can attest the brakes work great!
Setting them up there are a few minor differences, and I’ve got a couple little tricks to get them perfect. On a traditional brake, the pads will “self center” when you squeeze the brake, and if you don’t you can just twist them by hand until they are properly adjusted. Direct mount brakes do this differently, but it’s not any more difficult. Minor adjustments are easy with small set screws on the side that allow you to widen the stance of the brake and help you center pad contact on the rim. A couple turns with a 2mm Allen key and you’re set. Direct mount brakes also include another small set screw that allows you to adjust the spring tension. I like to dial up the spring tension on the rear brake to help it forcefully retract after going through so much brake housing. This is quickly and easily accomplished by screwing in the set screw all the way. With those minor tweaks, the brakes will be set up perfectly and you’re done.
Our bikes are set up with the TRP T930 (front) and T851 brakes (rear). The T930 is beautifully machined, 184 gram hunk of aluminum that combines elegance with performance. The cam-style quick release and in-place pad holders make setup and maintenance as easy as ever. It’s everything you’re looking for in a top-shelf brake. The TRP website conservatively claims you can set it up with tires as wide as 28c. In my eyes, that’s absurdly conservative. With our 28c tires from IRC in there we still have TONS of space. I bet you could squeeze in a 32 if you felt like it. Regardless of what they claim, the result is the same: there is plenty of space for wide rims and tires.
Our rear brakes are the TRP T851 side pull brakes mounted under the chain stays of the KTM frame. This brake is THE brake to ride if you plan on using a left crank arm based powermeter or have any concerns about crank arm clearance. The brake itself has clean look in a high-performance package, with a feather-like weight of 182 grams. It also has a good amount of leverage to give you a powerful brake. Plus, there is plenty of room to fit wide tires and rims in there. TRP also conservatively claims a max of a 28c tire, but you could go much much wider. Again, I bet I could fit a 32 in there if i felt like it.
But most importantly, the T851 brakes profile is narrow. A narrow brake in the rear is very very important. When I say narrow, I’m not talking about the amount of space left for the tire (as i state above, you can fit big tires in here). Instead, I’m talking about the outside to outside width of the brake (or how far it sticks out to the side of the frame). I only found one other direct mount brake as narrow as the TRP T851, and that’s the $630 eeBrake from Cane Creek. I’m sure the eeBrake brake is good and all, but that’s a huge price premium over the $119 TRP T851.
There are 2 downsides to this brake mounting position. 1) The brake is in a position that gets dirtier from road grime. Meh, that’s not really a big deal. You barely ever need to swap out brake cables anyway. Plus, with the sealed cable systems out on the market it doesn’t matter at all. 2) The brake mounted to the chain stay can stick out to the side and interfere with the crank as you pedal. With some brakes, this could be a major problem if you use a left crank arm mounted power meter, like a Stages or 4iiii. Luckily for us, TRP has thought this through and made an awesome brake that alleviates this problem. I’ll talk about our brakes in a bit.
The installation of a direct mount brake is no more difficult than a traditional caliper brake, other than the fact that you’re tightening 2 bolts instead of one. As always, I recommend toeing in the brake pads as they contact the rim to give a well modulated brake feel and reduce any squealing with carbon wheels. I like to do this by placing a business card in between the back of the brake pad and the rim and squeezing the brake. The small offset from the thickness of a business card gives you a perfect amount of toe in. The operation of a direct mount brake is the same as a caliper brake. There is still the normal cam that opens up to give you space to remove the tire just like you’re used to. The only difference is that you now have a brake that performs better!
I want to end this post by reiterating one point again, because it’s so important. Crank clearance is a major concern with bottom bracket mounted brakes. The T850/851 were designed to offer exceptional clearance, and it will work with any frame/crank combination you can find because it’s so narrow. It is absolutely the right and safe and (only?) choice for your chain stay mounted direct mount brake.
Hope this post helps you build up your new direct mount bike!