Tool time: rear disk brake piston compressor

So Jehu is always coming up with solutions to problems that either only appear in his mind, or the solution is so expensive there must be a quicker and easier way. Often fuelled by little time, and a need to finish a job once its started. The bodges slowly got more functional to the point where it is the tool of choice when doing the job, here is a case in point.

Problem: Rear disk brake pistons with integral handbrake. As the pads wear these unscrew on a internal thread in order to maintain the operation of the handbrake. Unfortunately this means that you have to screw the pistons back in when changing the pads. You can buy a tool to go on a ratchet, but you also have to put significant pressure onto the piston to make it engage on the thread. This makes it fiddly, An easier tool to use is very expensive, and that goes against Jehus prinicples for something with little use that can't be very complicated.

So here's the solution. We use a G clamp to press the pistons back on the front brakes. That works on a threaded principle so there must be something in it.



There was! Take a drill, a clamp or vice and carefully drill a hole about 3mm through the collar and shaft of the threaded part of the clamp. Find a blunt or snapped drill bit/pin/nail the same diameter. Place through the hole as pictured. Tape up so it doesn't fall out. BINGO! In effect you have removed the free rotation at the collar so now as you tighten the clamp, the end is also rotating.
This means that as you tighten the clamp to compress the piston it is also screwing the piston back in, and if the threads are different any difference is made up in slippage at the contact point, it seems to work really well.
And as a bonus it still works as a normal clamp if you remove the pin/nail/drill bit.
Job jobbed