Are there any parts replaced in the process? Or is it just a tear down, clean, lube, rebuild?
The seals get damaged by grit and dirt thrown up from the road allowing dirt to build up on the piston walls this means the piston cannot move freely, so it will not retreat after braking or, more seriously, not extend so the brake will not work.
Some calipers seem to be more susceptible to dirt build up, especially those slung at about 5-7 o'clock as you look at the disc. The process of servicing them is not difficult, but you might think twice about doing it yourself – for obvious reasons they are fairly important.
Generally you can replace the seals, clean up the pistons and flush through with brake fluid before bleeding (fit a new bleed nipple too) – you might as well fit some new pads at the same time. But if the piston is scored then that will need replacing.
Tip –?use the brake hydraulic system to pump out the piston(s) – do not pry them out with molegrips you will certainly damage the walls, there are special tools that fit inside the piston.
The parts should not cost much.
For any vehicle brakes are important and should be reviewed as part of a regular maintenance schedule. For the bike in question, if you are lucky you can research and determine:
a) manufacturer's recommended service interval for brake caliper rebuild
b) how long has it been since previous owner serviced the brakes?
c) was correct service previously performed at the recommended intervals?
I can't answer your specific "typical scenario" question, other than to say that the typical scenario is that there is a guy called a mechanic that is qualfiied to tell you what is needed, and there are random chuckleheads on youtube and yahoo answers that may or may not be giving advice above their pay grade. How much is free advice worth? Brakes aren't something you want to fix in a halfway-too-clever way.
A caliper rebuild consists of O rings , a dust boot and a thorough cleaning . If the caliper is so shot the piston has seized ( not just sticky but locked up ) you will want a new caliper .
Depends on the damage. If it is seized because the pads got too low and the pistons came too far out, then it should just be disassembly and reassembly. New pads of course. I think the last one I had done was 2hrs labour.
If the brake is not working to it's highest performance.
you might want to buy a new caliper, and the pads that fit in the caliper, dont forget the brake fluid
bicycle?
