Disk Brake Power Loss

CharlieV453

Hi there!
I know the story of squeaky brakes and if you contaminate them they squeal and lose power. However, my brakes were working fine and I hadn't recently cleaned my chain. After locking up my bike and leaving it for a few hours, the brakes had lost power, started squealing and when i wiped my clean finger over the disk it came out dirty.

Does anyone know why and how this could happen.
I do know how to fix it however but the repetition is getting irritating
Thanks

robertpb

Go to Halfords and buy a can of brake cleaner, it's cheaper than buying bike specific cleaner.

FishFish

No reason why the brakes should not be dirty - could just be dust. It is cold and humid at the moment which would hold the dust. Look up bedding the brakes in by going down a slope and going hard on the brakes. Alt - and I do this myself - remove the pads and score them with the edge of a file. I do that on the principle that it stops the pad exciting a standing wave in the disk. Seems to work anyway. Try Kevlar pads in future or best of all -= give up braking.

FishFish

...and clean the disk with Methylated Spirit or denatured alcohol as it is alternatively called. If you are buying it from the chemist then try not to look too rough.

The Rookie

Do NOT use a non bike brake cleaner, the brakes on bikes don't get hot enough to burn off the residue. Rubbing alcohol is best.

CharlieV453

Thank you all for your help. I have tried the methods given to me and they work well. The problem is now fixed and my brakes are working well. Thanks

CharlieV453

FishFish wrote:

No reason why the brakes should not be dirty - could just be dust. It is cold and humid at the moment which would hold the dust. Look up bedding the brakes in by going down a slope and going hard on the brakes. Alt - and I do this myself - remove the pads and score them with the edge of a file. I do that on the principle that it stops the pad exciting a standing wave in the disk. Seems to work anyway. Try Kevlar pads in future or best of all -= give up braking.

Thank FishFish for your help. The brake pads weren't new enough to require bedding in and weren't old enough to need replacing though but the idea with a file sounds like a good idea. Thanks

FishFish

I'll send you one inside a cake.

CharlieV453

I have also noticed whenever I clean them and put them back on the bike and start braking they instantly become dirty and glazed but how can this be possible if both the rotor and pads are clean?

Lagrange

Coulds be brake dust, caused by wearing - have a look round the disks on your car for example.

The Rookie

They can't instantly become glazed, hat requires heat, they may instantly become something but it IS NOT glazed!

cooldad

99.9876545668899% of brake problems are caused by random uneeded faffing

CharlieV453

Yes have just been told it is contaminated not glazed but the surface looks similar so I got confused. Sorry! They do continually become contaminated though. I have been told this could be dirt trapped in the gaps of the brake rotor but I have thoroughly cleaned it twice. Another possibility I have been told about is that my brakes are "misting". I think this is when there is a leak and the oil goes onto the rotor every time you pull the rotor. This sounds highly likley. Does anyone know a fix for this? Thanks

cooldad

Do you really need 2 threads on the same thing?

cooldad

Rebuild the calipers if you can get new seals, or replace. But I doubt that's the problem.

The Rookie

You'll probably find the contamination is soaked into the pad, it's more than a quick wipe over to get the contamination out, you can clean the surface but as soon as you use them it will come back out.