Can disc rotors 'go bad'?

horrible squeaking noise.

Is that while pedalling or applying the brakes? I have similar on my Bizango when pedalling, and every time I clean the bike I end up having to reposition calipers. I'm sure there's something else I should do but this works, at least for a couple of rides. Squealing brakes in use - I simply don't go fast enough to create heat when braking 😂

have you measured the thickness. i replaced one that had worn right down to 1.1mm recently and its transformed the performance of the brake.

I know you say there are no signs of weeping, but they probably are with everything you describe.

RT-54 rotors are fairly soft and could well have worn. Have you run a finger over them to see if they are scored or have a lip on the edge of the braking surface?

The other possibility is that if you've changed the pads for a different compound or supplier, you may be struggling to lay down a suitable boundary layer on the rotor. If the rotor is in good enough condition to try saving, try a bit of wet and dry in circles to dull the surface lightly. Then clean thoroughly. I tend to use washing up liquid and a tooth brush, then IPA.

Then bed the pads in again by pedalling along with the brake on. Don't do hard stops as this can leave an uneven layer. The idea is an even costing applied by heat and pressure. You'll feel a stop change in the brakes when this works. Go a bit longer after this just to be suit.

Anything used on the road is always worst for getting contaminated due to oil and shite from cars getting 9n the rotors.

dawson
Full Member

I know you say there are no signs of weeping, but they probably are with everything you describe.

Agree. Fought this for yonks on my bike. There was no sign of oil in the caliper, on the pads etc. Nothing. Just the hideous honking noise.

I'm not sure - but I have certainly had a similar issue on an MTB. I couldn't get my brakes as good as I felt they should be based on others, until I changed the rotors and they were immediately great again.

It's hard to come up with a theory as to exactly why, but it certainly happened. Weeping is another possibility, especially with DOT as it can be hard to spot - it will dry up and/or wash away with water eventually but you still could have residue.

Also the cheap Shimano rotors, whilst wonderfully affordable, are a bit shite and pretty noisy. The ones that came on my road bike (Ultegra/105 mix) would squeal in the wet, from new, but it got worse and worse and eventually were squealing like mad all the time. I've replaced them with decent Ice-tech ones, I didn't even change the pads (although I did sand them down) and it's been fine.

Rotors wear out and sometimes unevenly giving the squeak and occasionally a pulsing effect when braking. Daily commute use will mean a higher wear rate than on an MTB just used at weekends. New rotor and pads should solve it.

It sounds like a caliper leak.

I know you say there are no signs of weeping, but they probably are with everything you describe.

Bit ambiguous!

Recently had this. Tried everything, bleed and thoroughly clean caliper with IPA, thoroughly clean rotor with IPA + rinse with water, heat pads and lightly sand, and it would work for a week before returning to noisy bad performance. Tried new rotor and new pads and still really bad noisy performance. Had a spare caliper, swapped it over, re-bled, been perfect for 3 weeks so far.

Yeah my money is on a leak. I’ve just sent a 10 month old deore 4 pot caliper back as it developed these symptoms but would improve after the first decent descent once it was hot. The pads seemed sticky on one side so I think the opposing pads were coming out further and seeping oil. With pads out if you pump the lever do both pads move ok?
I watched a video where they cleaned the outside of the pistons and removed a lot of built up crud which will probably lead to tiny leaks. If they are out of warranty that might be worth a try?

https://www.pinkbike.com/video/478889/

I had Uberbike pads on my mtb recently and they went off.  They just stopped biting at all like they'd turned to stone.  Switched to genuine Shimano and everything is fine.

Is there a rotor that everybody loves?

My experience with cheap shimano calipers is that they kind of 'mist' oil from everywhere! If you're lucky enought to have a post mount frame, swap some deore calipers on to them.

Is there a rotor that everybody loves?

SRAM Centreline works well on all our bikes. Hope floating also worked well but spendy...

Sounds a bit like my Tiagra calipers, which were leaking onto the rotors.

But if you want to try new rotors, there are very reasonably priced pairs of Clarks ones on eBay which I can recommend.

Thanks for the replies everyone. It's very much a honking noise under braking and you can almost feel the slip of the pads. I suspect it's the calipers weeping as if I deliberately drag the brakes the heat does help for a shirt while. I've an old set of working maguras which I will swap over and see what difference that makes

It’s very much a honking noise under braking and you can almost feel the slip of the pads

That's exactly what mine was - "honking" - no more precise word for it!

Right, update in case anyone has a similar issue. Replaced with Magura MT Sports f and r. These work fine now on the same (cleaned) rotors. Nearly stripped the thread on the lever shortening the hose mind you but got away with it.

My slx brakes were bloody awful. New shimano ice tech rotors and shimano resin pads ,performance is now all I could hope for.

I think where you going wrong is cleaning the rotor with IPA. When people say: crack a beer and fix your bike, they mean you drink the beer, and use something else to clean your bike.

On a serious note, I first check the thickness like mentioned above. I would have to think the rotors would be worn way past good thickness with that much use, even if you were not having specific issues.

Yes, I did check the rotors and they are fine thickness wise. The brakes were only 18 months old (brand new bike) and we're still on the original pads which were maybe 40% worn. It's a commuting/town bike do not subject to a huge amount of abrasive grit.

Must admit I'm very disappointed with the lack of longevity. I've put in a warranty claim but don't fancy my chances

have you measured the thickness. i replaced one that had worn right down to 1.1mm recently and its transformed the performance of the brake.

Check this.

I struggled for ages with my Hope Tech E4s and them underperforming. Eventually it dawned on me that my trusty floating rotors were actually quite old - I measured them (only with a flat blade caliper, not a true open jaw micrometer) to be at or near the min thicknesss. Replaced them with bog standard new Hope rotors - braking performance immediately redeemed.

I had similar issues with SRAM rival. It was leaking callipers.

If I suspect a leaky caliper and the weather is dry then I use a bit of talc/baby powder. After a decent ride it'll show weep/leak.

Goes out to the bike shed with the talc.... and it's not too fit a new tyre....I think I may have the same issue.