Disc Brake Contaminated After Every Wash

Greetings everyone, I’m having a really annoying problem with my ultegra front brake that I’m looking for advice on. Pretty much every time I wash the bike (even with just water) my front brake is squealing and weak after, only improving if I fully clean the pads and rotor with isopropyl alcohol. Today I tried taking my pads out before washing the bike and it still happened. In this time I’ve tried replacing my pads, rotors, and even incidentally had the brake caliper itself replaced last year. There is clearly something that is getting washed into my brake when cleaning but I have no idea how and why especially if I’m taking my pads off. Other than accidentally washing the brak pad off of the rotor (which seems unlikely since I’m not directly spraying the rotor and it only happens to my front brake) I don’t know what the issue is. Any advice?

Buy a rim brake bike :slight_smile:

In all seriousness, I’d get a good mechanic to give the whole system a good bleed and a thorough once over. After that, if the problem keeps repeating itself, it’s tricky. Some squeal is normal with moisture and very hard wholly to eradicate, but it should only last minutes. As for weakness, did you properly bed the pads and rotors in? My only guess is that if you never fully bedded the system, you’re effectively washing off the deposited material on the rotor and reducing system efficiency. Lightly sanding the pads can also help.

I’ve had a proper bedding multiple times, both when I’ve put on new pads and when I’ve cleaned. Each time I’ve gotten it completely silent or pretty damn close. I know Shimano pads can be prone to being loud, but these get super loud and lose a bunch of power immediatly after a wash so there is clearly something getting into the braking system itself.

the only other option I’ve considered is that the pistons themselves are leaking and everytime I wash the bike it’s washing brake fluid on the braking surface/pads. I had my front brake replaced under warrantly last year for a sticking piston and it is still happening after though so I’m not sure how likely that is.

I don’t know about your specific situation, but the two times that I’ve battled recurring brake contamination it ended up being leaking calipers. Mine didn’t have any correlation to bike washes though.

I’m starting to suspect this might be the issue since I’ve checked just about everything else. Will try taking the bike into my LBS to see if they can verify and potentially warranty my caliper. With supply chain issues hopefully they can even get one.

From your description I also suspect a leaky caliper. Good luck solving it!

Hmm, I never had a similar issue and never heard of it (though I have to admit that I just clean my discs when I clean the whole bike, too). Even more strange that it’s in the front. I’d assume that contamination from cleaning would rather occur on the rear wheel since that’s where the cassette is.

I’d also suspect a leak in the system somewhere. Or maybe you’re washing some grease from someplace else on the brake, headset or something? Theoretically It could also be the way you clean the bike, using a contaminated brush, for example.

Have you tried shower caps or sth similar? I’ve heard that this could help in minimizing contamination - not that I’d have any experience from this, sry…
Try sealing the rotor and caliper from the spray, but be careful when hosing it down. Usually you can’t get it very tight and it easily blows off… :face_with_monocle: Good luck :muscle:

1 Like