What am I doing wrong with disc brakes?

Both my summer bike and all weather commuter have disc brakes.

The summer bike has SRAM Red Disc brakes - when it gets wet the brakes squeal for while while wet but then once dry are fine again.
The commuter has 105. Gradually over the course of a few wet rides they get louder and louder and weaker and weaker. I’ve tried cleaning with muc off disc brake cleaner and isopropyl alcohol but nothing fixes them other than changing the pads and rotors for new.

Is this normal? What could be causing this? I can’t afford 4 x new rotors and pads per year!

Perhaps you can use different sort of pads, organic ones tend to be quieter than metallic ones but wear faster; but squealing tends to be common with discs.


Agree about trying other pads. Especially if they get weaker and not only louder, that sounds like the pads can’t cope with the conditions.

However if you want a cheaper fix, instead of changing the pads for new ones, you can also sand them down slightly to remove the top, contaminated layer. You can also sand down rotors, but in general that shouldn’t be neccessary.

I’ve had cable discs that squeeled, but now only have hydraulic ones and minimal problems with squeels. One brake that I could never get quiet was a front disc brake on a QR frame. I think the QR wasn’t strong enough, leading to slight movement and slipping and then squeeling when braking. The rear was also QR, but because of the drivetrain, everything was a bit stiffer. If your frame is QR, that might be the issue. I haven’t got a solution, I just avoid disc brakes on QR frames now.

A third problem can also be if the place where the caliper is fixed to isn’t perfectly flat, and the caliper can vibrate slightly. Then you need to face the caliper mounts and make them properly flat.

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Sounds like something is contaminated the 105 brakes.

No idea what’s in the MucOff but I do wonder if that’s making it worse. I try not to get anything on my pads but water.

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Might seem like a dumb question, but do you have the correct size rotors installed? For example if you have 140 rotors installed in a 160 setup, your stopping power will be poor and you are going to burn through pads like crazy.

I don’t know if it’s always the standard but both of my road bikes run 160 front, 140 rear. I made the mistake of putting a 140 rotor on the front on one set of wheels and it took me about a week to figure out what I’d done… but loud, eating pads, and stopping power was crap.

Kinda left field here, but the 105 bike is the commuter bike, which sort of implies you experience the problem after a few wet commutes. Are you riding through stuff that’s contaminating the rotors/pads? Oily puddles maybe? Admittedly, low probability, but nonzero.

Also, you should be able to clean the rotors for sure, and I’ve rescued pads from mineral oil contamination with a short soak in acetone, then denatured alcohol, then sanding with 100 grit sand paper. Not the best thing, but when they’re the only pads you have on hand, and have to get them working, you do what you must.


Thanks for the replies.

I’ve tried every combination of pads, but once the contamination is in then nothing works.

My commute is 80% gravel tracks 20% road, so not exactly and extreme use case.

Is it possible the pistons themselves are passing oil onto the pads? Dodgy seals maybe?

I feel like the system should be able to withstand a few wet rides without completely packing in.
Granted I do less wet riding on the SRAM bike but I’m getting over 2 years out of the brakes and pads on that bike with no issues other than a bit of noise when they get wet (which dissipates when they dry off)

Piston seals can leak, but then you’d lose oil, and the brakes would feel like they need bleeding.

You could probably buy new calipers, if you think the seals are bad. It might be possible to replace the seals, but new calipers for 105 are likely not that much more than replacing rotors, pads, etc, a few times a year!

Sandy grit can absolutely destroy brake pads very quickly (a few hours), especially organic ones. If your commute is mostly on gravel, I’d definitively go for sintered/metallic pads. They are louder, but they last longer and cope with wet better.

Absolutely true. But you’d also see the wear on the pads (pad material is thin, likely with gouging/rough patches).

How do the brake levers feel? Is system pressure, lever pull, etc feel normal?

Do the pads looks glazed/smooth?

Could also be sticky seals in the calipers. Searching online should get you options for resolving that problem.

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Are you bedding in the new pads properly? How you treat the pads (and rotors) in the first few miles can make a huge difference in long term performance.


Disc brakes squeal when wet… that’s just the way it is. You haven’t lived until you’ve heard 100 cyclocross riders coming into the first turn of a wet race. I have found organic pads are quieter in the wet than metallic pads. Organic pads wear faster, but for road riding it really shouldn’t be an issue. It’s more an issue for off-road stuff with mud.

Brakes rotors should only need replacement very very rarely. Even if they get contaminated they can be cleaned up nice with appropriate chemicals (soapy water maybe, isopropyl, automotive brake cleaner). Brake pad material does kind of build up on them so if they could transfer the contamination to fresh pads, though. In the absolute worst case you might need some fine grit sandpaper to lightly abrade the the braking surface before the chemical cleaning.

As for pad contamination… same deal. Brake pads can “glaze” over. Take the pads out and a) clean with brake cleaner b) lightly sand the surface, and c) clean with brake cleaner or isopropyl again. If that doesn’t work, the pads are toast.

Always re-bed the brakes after using brake cleaner spray or sanding. Simple soap-washing of bike components shouldn’t require this.