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I put new rotors and pads on my wife's commuter bike a few months ago (Uberbike race matrix pads, non-resin-specific rotors). They were silent at first, and now they HOWL and don't stop well. Front and rear behave the same.
There's lots of pad material left. I cleaned the rotor and pads with alcohol, pushed the pistons back in, and realigned the caliper--none of that made a difference.
I'm not used to winter (moved to Scotland from California recently)--is this a road grit/salt contamination issue? If so, is there a better pad choice? A maintenance/cleaning protocol? I'm at a loss.
Thanks for any tips!
contamination more than likely. When I used to commutte I found the bike needed a really hard stop every few days to prevent it. The problem is disc brakes rarely get to operating temp in winter in Scotland 🙂
It could be the shimano micro leak tho if cleaning it did not help
Dab of grease on each pad will make them much quieter.
I found that commuting never really shows you to put heat into the pads and discs so they tend to squail. Every now and then I take my commuter on a ride with some decent descents and do some sustained braking.
It will be contamination.
The only reliable way to recover the pads is to burn it off. With the contamination the friction is reduced so you won't get the temperature high enough to burn off the contaminant just with hard braking. A blow lamp works well - remove the pads first obviously! BUT be careful to heat the pads gradually, heat them until they stop smoking then let them cool naturally. Now, (and I must stress this is really important) give the friction material a good hard tap to make sure they are still firmly attached to the backing plate, as extreme heat can break the adhesive. From my LBS days I've done this maybe 500 times with only a couple of failures so it's unlikely but you need to be aware of it.
The rotor can be done with a blow lamp as well, but keep the wheel spinning so the disc gets heated evenly and make sure the calliper is not in the line of fire of the blow torch if you leave the wheel on the bike.
You don't have to get everything very hot, just hot enough that that start to smoke.
If you aren't happy trying it then clean the rotor with neat washing up liquid then sand lightly and buy new pads.
Erm...all my brakes squeal? I'm guessing cos I'm not gnarr enough either commuting, gravel-ing, or even trail-ing. Very occasionally, on holiday trips to Laggan et al, I lose some squeal...well,from the brakes anyway 😂
fazzini - big discs? Small discs get hotter so keep it more in the right range. disc brakes need heat to work properly
It could just be the pads. I bought some cheap nonShimano ones when the D03 Resin ones were out of stock everywhere and they squealed constantly no matter what I did to them - cleaning, sanding etc. I put some Shimano ones back on and problem went away immediately. Only time they squeak is when riding in the wet, soon as it’s dry they stop.
Thanks, everyone! I've ordered some new Shimano-brand pads (K03S, hard to find in stock right now). Once I have them in hand I'll try torching the old ones. I tried that once with a previous set of pads and almost instantly separated the pad from the backing plate (as Boris describes)--I'll try to be gentler this time.
I've been plagued by squealing disc brakes (albeit only in the wet) and have plagued this forum in turn moaning about it 😎
I had dismissed suggestions that the brakes weren't bedded in properly as I had been through the whole '20 hard almost stops' rigmarole, but last weekend I was out on the MTB in the sort of slushy wet snowmelt conditions which would usually result in an exceptionally deafening performance from the brakes, but instead they were almost silent, bliss!
I think the difference has been actually using the bike as a mountain bike on its last couple of outings, and doing lots of heavy braking on long steep fast descents, which I *never* really do on road or gravel.
I looked at Swissstop's instructions for bedding pads and rotors in and noticed they suggest several hard 20-30s stops, which when you think about needs a substantial hill, not just sprinting up and down the road outside your house!
TLDR? Bed your brakes in by panic braking down long rocky Cairngorms descents, then swap them over to your commuter 😎
Any change in the brake feel or significant change in stopping power. I've had a couple of sets of shimano calipers fail at the seals. They leak a small amount of fluid onto the pad, causing an awful squeal.
Thanks again, all. I took the bike down a 7% 2/3-mile descent a couple times, heavily dragging one brake each time (resulting in going at about jogging speed). Each brake got noticeably better by about halfway into the 5-7 minute descent. An earlier attempt down a longer but less-steep road didn't make a noticeable difference.
fazzini – big discs? Small discs get hotter so keep it more in the right range. disc brakes need heat to work properly
Not really @tjagain think my Diverge has 160s on it; the Bizango has 180/160 - I expect the Sommet to squeal as its 200mm rotors will never get hot enough with me riding it (on the plus side my screaming drowns out any brake squeal 😂) - but to be fair to me there are no big hills around my way so options for bedding in properly are limited. Tanners Bank just aint long enough 😉
"Dab of grease on each pad will make them much quieter."
Depends which side you grease...