From the mount of peak stupid

Kaleidopete

Kaleidopete

Well-Known Member
I've been getting a "grumbling" from my rear brake.
When I changed the pads last week I noticed a "ridge" on the upper part of the pad made by the rotor not quite reaching the top of the pad.
My new pads now are showing early signs of the same thing happening. I never noticed this before on any pads I've replaced on any bike.
Is this something new with 4 piston calipers? Trek bike Tektro HD-M745 caliper.

poor drawing
Pro_EBike_Pads.jpg
 
Pete, I think your caliper needs to come in towards the axle enough to fully wipe the pad. Probably another 0.010-0.015” more than the thickness of the ridge on the pad. Maybe one less washer or a thinner washer under the caliper on both mounting bolts if it is a post mount. Oh, and new pads if the ridge is pronounced. Or just run it after the caliper adjustment and gingerly brake til the ridge grinds away and you have full pad- rotor contact.
 
I noticed this happen to my 4pots as well. Totally stock Giant Reign that has 200mm rotor, with MT520's on a Yari. I took a razor and cut down the ridge, then sanded/cross-hatched the pads and rotor. Haven't seen it come back since.
 
auntjemima said:
I noticed this happen to my 4pots as well. Totally stock Giant Reign that has 200mm rotor, with MT520's on a Yari. I took a razor and cut down the ridge, then sanded/cross-hatched the pads and rotor. Haven't seen it come back since.
Click to expand...
The op doesn't say what diameter his rotor is but in your case swapping to a 203mm diameter should correct the issue. Shortening every pair of new pads you install from now on is sacrificing braking performance.
 
TJYeti said:
The op doesn't say what diameter his rotor is but in your case swapping to a 203mm diameter should correct the issue. Shortening every pair of new pads you install from now on is sacrificing braking performance.
Click to expand...
Thanks, sorry about the rotor it is a 203mm
 
Kaleidopete said:
I've been getting a "grumbling" from my rear brake.
When I changed the pads last week I noticed a "ridge" on the upper part of the pad made by the rotor not quite reaching the top of the pad.
Click to expand...
Hey Pete, might help if we saw how many washers are stacked between the brake caliper and the mount. Like someone else said, you probably just have to remove a few small washers to get that caliper to sit a bit lower. Once you get that caliper to sit a bit lower you should take the pads and file that ridge down so that that rotor meets a uniform surface on the pad.
 
I had this happen. I only noticed it when swapping in a different wheelset and getting a scraping sound. The original rotor has a wavy circumference, the swapped in one has a smooth circumference. The wavy style left a ridge in the pads.
 
sundaydoug said:
Hey Pete, might help if we saw how many washers are stacked between the brake caliper and the mount. Like someone else said, you probably just have to remove a few small washers to get that caliper to sit a bit lower. Once you get that caliper to sit a bit lower you should take the pads and file that ridge down so that that rotor meets a uniform surface on the pad.
Click to expand...
no washers here. I have a plan, file down the block about 2mm.
Dsc07603.jpg
 
Kaleidopete said:
I don't think so, it's never been off since new, maybe I could flip it now and see how that works
Click to expand...

i think i changed my mind. but probably worth playing with? Gotta take it off anyway

or it is just the wrong one.
 
For giggles I removed the front caliper which is the same and never been off the bike either.
It's the same condition there. Here are photos of pads and rotor.
I guess I'm looking for perfection in an imperfect world. Just keep riding it and shut up.

see ridge upper edge
Dsc07606.jpg


again
Dsc07607.jpg


see rotor, no ware on lower section
Dsc07608.jpg
 
Weird. It’s close but the design tolerances should guarantee the braking surface of the rotor to overlap the pads top and bottom.

The caliper definitely needs to move towards the axle based on your pad and rotor wear. I’d flip the bracket before you start filing; it may be just enough to get you there.

At this point you prolly need a new rotor too. I believe you have had this issue since new.
 
Kaleidopete said:
For giggles I removed the front caliper which is the same and never been off the bike either.
It's the same condition there. Here are photos of pads and rotor.
I guess I'm looking for perfection in an imperfect world. Just keep riding it and shut up.

see ridge upper edge
View attachment 174972

again
View attachment 174973

see rotor, no ware on lower section
View attachment 174974
Click to expand...


id also look into sticky pistons, that brake pad on the left doesnt look evenly worn down.
 
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