Mysterious Pad Contamination

Three times in the last couple of months I have lost all function of the rear XT disk brake on my bike following a local, primarily street and towpath, ride (can barely lock up the rear wheel – braking simply has no effect). I replaced the pads and cleaned the disks the first two times and the brakes returned to normal function. I haven’t fixed the problem yet for the third occurence of the issue but I am sure changing/cleaning the pads and disk will sort it out.

I am pretty confident the brakes aren’t getting contaminated in my shed and can only think they are getting oil/diesel on them from the road during my ride. Is this likely/possible? Has it happened to anyone else? It is really getting on my nerves.

Are you using an oil spray on the chain?

could the caliper be leaking???

i doubt your picking up anything off the road, and if you did i wouldnt expect it to re-occur

from my experience of running these, mineral oil escapes around the caliper seals and over time, will contaminate pads, therefore each time you clean they return to normal, once being used the calipers deposit oil and the pads fail

I had similar on my saint front caliper, as the piston seals were seeping oil very slowly. It was getting on the pads and disc in small quantity and killing the pads.

With the wheel in, get a torch and get someone to pump the brake lever while you light up and watch the piston/caliper body seal area. If you can see bubbles or oil ‘pulsing’ in time with the piston moving then you may have a leak.

Thanks guys. I will investigate a leaky caliper – joy.