Brakes

The rear wheel must be removed to access the rear brake pads. But there is a catch. In order to remove the rear wheel, the rear caliper must be removed. Removing the rear caliper is accomplished by removing the rear master cylinder, hose, and caliper as an assembly (while removing the rear wheel). Of course, to get the rear master cylinder off, the rear fender must come off. Nothing is easy.

The single most important spare part to have on hand is a pair of rear brake pads. You will probably go through rear pads twice as fast as front pads. It is also not easy to see how much friction material is remaining with the rear wheel installed. I love EBC pads and use them for all motorsports. According to my EBC contact, the X-suffix pads are supposedly gripper but I have not really noticed a difference. Below are some of the equivalents I have identified:

Rear Pads: Galfer FD224 EBC FA351, SBS 803, Ferodo FDB2127, Vesrah VD9003 (I do not recommend using the Jitsie / GoldFren 173. They are very hard and useless in my opinion.)

Front pads: Galfer FD223, EBC FA303, SBS 802, Ferodo FDB2109, Vesrah VD9001

Rear master cylinder rebuild kit: Braktec 853028MO0

Front master cylinder rebuild kit: Braktec M853001MO0 (newer style)

Front master cylinder rebuild kit: AJP M CYL RP KT 1007 (older style)

Although it is physically larger, I actually prefer the old AJP front master cylinder over the Braktec used on later bikes. To me, the brakes have a better feel with the AJP. It is possible the lever ratio is different as they both use 9.5mm pistons. If you are looking to upgrade the front brake, Braktec's Monoblock is a very nice caliper. I have only ridden the cast model, but imagine the much more expensive CNC machined-from-billet version is ever stiffer.

The Tapered Wear Problem

All brake pads wear tapered. If I am going to reinstall the same pads (after cleaning, for example) I mark the pads as inboard and outboard with a Sharpie pen to make sure they go back the same way they came out.

But excess taper causes a problem. With the pads removed from the caliper, hold them together and measure across the outside of the pair. A new set of EBC rear pads measures about 11.8mm. For comparison, an old worn pair can measure 9.89mm on the leading side and 10.85mm on the trailing side. Although there’s still significant friction material remaining, that much taper is unacceptable.

A back-of-the-envelope calculation shows the mechanical ratio of the rear brake lever to be about 3.45:1 (your foot moves 3.45x times farther than the piston in the master cylinder). I think the rear caliper uses a pair of 25mm pistons. The master cylinder piston is 9.5mm. This yields a hydraulic ratio of 13.85:1. The combined (mechanical x hydraulic) ratio of 47.8:1 means your foot must move about 48mm to take up that 1mm of pad taper. Now there's probably some bending and flexing going on, so maybe your foot does not need to move the full 48mm before some braking occurs, but it illustrates the magnitude of the problem. Combine this with the sponginess of an imperfectly bled system along with any contamination on the pads, and you have an ineffective rear brake.

For reference, a good system may only need 15mm of foot travel to cause the brake to actuate.

I've never tried to sand the taper out of trials pads (there's not much friction material in the first place) but it could offer a quick fix in a pinch. (But be forewarned, there may not be sufficient fluid in the reservoir to accommodate that much caliper piston movement without topping up.)

Steam-Cleaning Brakes

Brakes contaminated with fork fluid or chain lube (and likely some “cleaners” as well) simply do not work. The best method I've found to remove this contamination is to get the rotor very hot and splash or spray water onto it and as much of the pads as possible.

The first time I used this “steam cleaning” trick was with the bike running on a stand while strapped to the trailer. It was the rear, and I just applied brake pressure while the wheel was turning. I used an IR thermometer to monitor the rotor temperature (which is completely unnecessary). I could smell the pads and see them smoking, but the thermometer only said 140° F. I ran it a while longer, but still only got to 200° F. The rotor seemed extremely hot. Splashing water on both sides produced lots of steam (and a big improvement in braking performance).

My advice is to just get the rotor so hot you can smell the pads cooking. More than one application may be helpful.