hello, i changed the the thing inside the back brake master cylinder and i left the bike for about 4 weeks,now the brake works a little bit but it sqeeks like hell. if i wet the brake disc it works perfectly it only takes a tap to lock the wheel up on concrete. does any body know the problem?

Try removing the pads and put a thin smear of copperslip grease on the back of each brake pad. This helps dampen the vibration that causes the high pitch squeal.

cheers, i'll try it if i can find any and will it solve the problem of it not working apart from when the the brake is wet

Edited September 1, 201411 yr by tjday

You need to give a bit more detail because I'm not sure what you mean about it not working, if you can lock the wheel up its working and it should do this if wet or dry.

The grease is only to stop it squealing and it works on all brakes.

when the brake disc and pads are dry they dont stop me or lock the back wheel up and just squeek but when i wet the disc and pads they work fine and lock the wheel up. im sorry if its confusing but thats what its doin.

Hmmm, That's a new one on me as I've only known this the other way round.

It seems what you did to the master cylinder is working okay,

It must be just an issue with just the pads & or disc.

Are they new or old pads?

Old pads are they Glazed?

Are the pads or disc contaminated with brake fluid or anything else like 'after wash spray'?

sorry for the late reply, been stuck at work

the pads aren't that old really and i washed all of the brake fluid off with a pressure washer and how do i tell if the pads are glazed?

They are glazed when there is a hard shiny layer on the pads. You will notice the difference once you remove the glaze.

Did you take the pads out of the caliper when you used the power washer???

If not, take the pads out and clean them with sandpaper on a flat surface or a wire brush and degrease them with brake cleaner instead of water.

Brake fluid ruins the pads. Either get new pads or you have to burn the oil off. A propane torch seems to be the best method.

i have done everything you guys have told me but still no joy apart from i used some alcohol rub in stead of brakes cleaner. i noticed a lot of black stuff on the rag i used to clean the disc, is this what's causing the problems?

i have done everything you guys have told me but still no joy apart from i used some alcohol rub in stead of brakes cleaner. i noticed a lot of black stuff on the rag i used to clean the disc, is this what's causing the problems?

If this occured after you cleaned the pads, you weren't thorough enough, use sand paper and brake cleaner as stated before.

If the black stuff keeps coming off, the pads may be saturated with brake fluid. I would dump them and get some new ones, and in the future be more carefull with the brake fluid.

#1 Throw soaked pads away, else you will cuss and groan about how the brakes work.

#2 inspect that the 4 (2 per side) are moving in and out. BE CAREFUL, you can pop these out of caliper, I dont let that happen so I cant describe what other problems you face if you let this happen.

#3 Brake pads have a minimum thickness then they are TRASH. get a pair from dealer or something, compare yours. if they are worn too thin, brakes work like sheeit. they are cheap.

I like to take 200 grit (usa terms?) emery paper and scuff my discs, to help break in new pads. scuff, means lightly...