Bedding in Shimano Disk Brake Pads

19 replies · 839 views

TwoWheeler
177 posts
#1Jun 22, 2023, 9:59 AM
I am apparently Shimano-challenged, because I often have a hard time getting Shimano pads bedded in so that it doesn’t sound like I have a cat wedged in the caliper when I brake.

Strangely I have had no issue with SRAM/Avid, and it doesn’t seem to matter which Shimano pad compound I’ve used. I am also scrupulous about not getting contaminants on the pads or rotors.

I built a new bike with GRX 815 last year and did the “get-up-to-speed-and brake-to-walking-speed” method everyone else espoused…and still ended up with banshees in my brakes. I sanded down the pads and took emery cloth to the rotors a couple of times, but to no avail. I finally threw in the towel and bought new pads. I stuck the rotors in a lathe and emery-ed them to remove all traces of pad material.

So, how do I get it right this time?
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stu
646 posts
#2Jun 22, 2023, 12:49 PM
FWIW I've had no problems with SwissStop Disc E pads and they last forever.
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TwoWheeler
177 posts
#3Jun 22, 2023, 4:47 PM
stu wrote:
FWIW I've had no problems with SwissStop Disc E pads and they last forever.
I blame the operator, not the pads. I apparently got the Ultegra pads on my Slate bedded in properly - on two sets of rotors, no less, because I have two sets of wheels for that bike - because they have a VERY good bite and make no noise at all.

The Ultegras on my Roubaix are quiet, right up until you’re almost stopped.

The GRX brakes on my Carbonda go full banshee.
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SWGraveler
247 posts
#4Jun 23, 2023, 10:01 AMedited
I'm following this out of being new to disc brakes. I recently replaced the pads in the Ultegra calipers on my gravel bike for the first time and didn't do anything other than test ride to see if they made noise. I replaced with Shimano pads. They didn't and still don't. Maybe I just got lucky but I'm ok with that 🙂. Sounds like there can be a lot of effort involved if they are noisy!
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TwoWheeler
177 posts
#5Jun 23, 2023, 11:21 AM
SWGraveler wrote:
I'm following this out of being new to disc brakes. I recently replaced the pads in the Ultegra calipers on my gravel bike for the first time and didn't do anything other than test ride to see if they made noise. I replaced with Shimano pads. They didn't and still don't. Maybe I just got lucky but I'm ok with that 🙂. Sounds like there can be a lot of effort involved if they are noisy!
My understanding - which, given my history may be deeply flawed - is that it’s the initial bedding in that’s the issue. Fresh rotors need pad material bonded to them to work properly. If the material that’s transferred is uneven, that’s what causes the howling. AFAIK, that’s why you don’t come to a complete stop while you’re doing it.

In your case it was right from the get-go, so simply replacing pads isn’t a problem.
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Mtnfun2
27 posts
#6Jun 25, 2023, 6:01 AM
were the old brake pads noisy cats? if yes something is on the rotors put rubbing alcohol on a paper towel and clean those rotors, if you have greasy hands don't touch your rotors. You may get lucky with doing the same to your new pads if they are not heavily contaminated. Another option is using a very fine grit [think drywall paper] sand the pads and rotors to roughen things up. If you go this way, I suggest bedding in, go outside and make 5 long stops [think 10 seconds] separated by 30 seconds. Then make 5 quick stops [not skidding tho we do not want to lock the rotors when bedding in]. that should do it. Now if you accidently purchased metal pads, they will make noise, especially when wet.... stick with organics.
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TwoWheeler
177 posts
#7Jun 25, 2023, 8:32 AM
Mtnfun2 wrote:
were the old brake pads noisy cats? if yes something is on the rotors put rubbing alcohol on a paper towel and clean those rotors, if you have greasy hands don't touch your rotors. You may get lucky with doing the same to your new pads if they are not heavily contaminated. Another option is using a very fine grit [think drywall paper] sand the pads and rotors to roughen things up. If you go this way, I suggest bedding in, go outside and make 5 long stops [think 10 seconds] separated by 30 seconds. Then make 5 quick stops [not skidding tho we do not want to lock the rotors when bedding in]. that should do it. Now if you accidently purchased metal pads, they will make noise, especially when wet.... stick with organics.
Nope - brand new pads, brand new rotors - and I was very careful not to get anything on either one. I cleaned pads, rotors and calipers with alcohol and wore latex gloves.

The bedding in process I followed was something like “get up to speed then slow to a walking pace” 20 times with each brake.

It seemed to go ok, but after riding the bike for a couple of weeks, it started howling. I lapped the pads on emery cloth to break the glaze, took emery to the rotor, cleaned everything and tried again, several times, then threw in the towel and bought new pads.

I’m hoping to get it right this time.
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Mtnfun2
27 posts
#8Jun 25, 2023, 9:24 AMedited
Which shimano pads did you use. L04. Are metallic and can be noisy... I tossed my pair after my first wet ride.... L05 are resin, much quieter..... The code is stamped into the backer plate
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TwoWheeler
177 posts
#9Jun 26, 2023, 5:31 PM
Mtnfun2 wrote:
Which shimano pads did you use. L04. Are metallic and can be noisy... I tossed my pair after my first wet ride.... L05 are resin, much quieter..... The code is stamped into the backer plate
The ones I have now are LO5A. The ones I tossed were whatever came stock with the 105 calipers.
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bnystrom
459 posts
#10Jun 29, 2023, 6:18 AM
I hate to say it, but the problem may not be easy to solve, as it may not be just the brakes.

My girlfriend has a Pivot LES that she loves, except that the (Shimano) rear brake absolutely howls. In contrast, the front brake is dead-quiet. I've tried three different types of rotors (including slotted), at least four different pads (mostly organic), mixing organic and semi-metallic pads, applying Brake Quiet to the back of the pads (a waste of time), and of course, multiple pad and rotor cleanings/sandings and bedding-in processes. Nothing works for more than a short ride. I've even tried grooving the pads to try to reduce vibration, which showed some promise initially, but ultimately didn't solve the problem. I've pretty much come to the conclusion that the problem is that the frame is allowing the caliper to vibrate excessively and is resonating that vibration. Unfortunately, there's no way to put any type of vibration damper between the caliper and the frame, at least not that I know of. Short of cleaning the pads and rotors after every ride, there doesn't seem to be a solution for this bike.

If anyone has any ideas, I'm all ears!
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TwoWheeler
177 posts
#11Jun 29, 2023, 6:44 AM
bnystrom wrote:
I hate to say it, but the problem may not be easy to solve, as it may not be just the brakes.
I figured it was the alleged mechanic….

I have some hope because I had the same issue on my Slate (although, to be fair, that was “store-bought”), with Ultegra brakes. I farted around sanding and stuff a few times and finally put new pads on and now have brakes that bite HARD and are completely silent. I also have two sets of wheels I swap in and out - one with Shimano rotors and one with Formula (?) rotors - and no issue.

I was tempted to swap in the rotors from the Slate to bed in the new pads on the other bike, but I don’t want to screw THOSE up too!
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bnystrom
459 posts
#12Jun 29, 2023, 6:46 AM
What pads did you use?
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TwoWheeler
177 posts
#13Jun 29, 2023, 7:26 AM
bnystrom wrote:
What pads did you use?
I’m not sure what the “stock” ones were, but I definitely have the resin ones now.
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bnystrom
459 posts
#14Jun 29, 2023, 7:30 AM
OK, I've already tried those.
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Mtnfun2
27 posts
#15Jun 29, 2023, 10:58 AM
Only other point I can offer is I had a pair of sram calipers that had a subtle leak at the calipers, which created a pad glazing squeak issue. I finally figured it out when I realized the outer edge of the rotor was black with coked oil.
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bnystrom
459 posts
#16Jun 29, 2023, 11:41 AM
I've seen something similar on another bike, but there's no evidence of that on this one. Everything is clean and tight, it just makes huge racket.
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TwoWheeler
177 posts
#17Jun 29, 2023, 2:13 PM
I have pads that work fine and rotors that work fine. I keep wondering if I used the new pads on the “good” rotors or the “good” pads on the new rotors if I can fix the problem….or just make more…🤨
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bnystrom
459 posts
#18Jun 29, 2023, 2:31 PM
There's only one way to find out...and no guarantee of success.
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TwoWheeler
177 posts
#19Jun 29, 2023, 3:44 PM
bnystrom wrote:
There's only one way to find out....
Someone else’s bike?
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bnystrom
459 posts
#20Jun 29, 2023, 4:22 PM
😂
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