Ryan_M

The rear brake on my roadie is driving me nuts. Been through a few brake pad sets, sanded the rotor (400SiC), also tried emery, chemically cleaned, still no difference. It's a 140mm MT800 rotor, are some just born bad? I'd rather not toss a rotor that has less than 1k on it but not sure what else to do. Next plan is to chuck the rotor in the lathe and take a pass to ensure a fresh surface - seems over kill though

Barry2 

Switch it & pads to the front.
see if the noise travels with the rotor.

Barry

Ryan_M

Good idea

mpetry912 

loosen the caliper bolts

pump the lever 3 - 4 times. in fact clamp the lever with a rubber band

then tighten the caliper bolts

Release the lever and ride it

basically align the caliper with the disc to ensure even contact.

/markp

maddog34

what type of pads are you using? Switch to Resin Pads to get rid of the squeal. Those discs will work with any pad type.

t2p

check the caliper alignment

after that check the caliper alignment

If it looks good still might be worth moving it to determine if a change will make a difference

some (many / most ?) calipers can be aligned with the method recommended above (loosen caliper bolts / apply brake / tighten caliper bolts) - but there are calipers that will not align well with this method and the brakes will squeal ...

cpach

Take a hard look at how well the caliper is aligned to the rotor in terms of yaw (ie, not the adjustment you can do moving the caliper by hand with the bolts loose). If it's visibly off, you might improve things on a number of fronts getting the caliper mounts faced. The tools for doing this are really expensive so this is a good one to bring to a good shop. I see a startling number of bikes with flat mounts with caliper mount alignment issues. The shop's tool is out for sharpening this week--it's been getting a real workout recently.

shelbyfv

Link to OP's previous thread, minimize rehash squealing brakes

Kai Winters

There is a product called "Squeal Out" that works great. It's not cheap but it works.
If the pads are contaminated there isn't anything you can do to remove the contamination, they have to be replaced or try Squeal Out. We use it at the shop to cure howling brakes and it has worked every time.

pit_usa

Where do you get Squeal Out?

Kai Winters

Google search is your friend

pit_usa

Thanks Kai Winters Just couldn't find it anywhere I've searched, thought you may know from somewhere... thanks though.

veganbikes

Ask your local shop to get it if they don't already have it.

GhostRider62

My front sram red axs disc has been a pita since day 1. I can get is quiet for weeks and then it squeals. I've replaced the rotor, pads (several times and different compounds), bled the brakes, straightened the original rotor, adjusted the caliper more times than I can count, cleaned the pistons. I do have a new caliper to try. The bikeshop that sold it to me a $13k bike was useless. One of the problems is they are prone to glazing when descending 15% very bumpy roads, I use brakes and they get too hot. The fix for that is simple, sand the pads and clean both rotor and pad with solvent. Then, bed them in again.

If I had to do it again, I would have waited for Shimano Dura Ace to become available. I suspect this is a SRAM caliper issue with inconsistent piston retraction and sticking

smd4

Did you even...try Google? Because doing so shows it's available at a number of retailers--including Walmart.

Ryan_M

I feel your pain. As someone alluded to above, this one brake has been a PITA for a long time. It was fine for the first couple months then crapolla. I did a bunch of things which helped for a short time. I haven't had a chance to swap to the front yet to eleminate one source of squeal but I suspect that will not solve the issue. You make an interesting point though about glazing.... mostly I use the road bike for club rides and we ride in formation most of the time so I tend to ride the rear brake A LOT! You might be onto something... I've lightly redressed the rotor by hand but haven't tried replacing it yet. I don't think I'll be able to mount it accurately enough to take a skim cut but I could be more agressive with abrasives. Thanks for the idea!

I run L03A pads (resin), I wonder if metalics might be better at preventing glazing?

GhostRider62

I've had better luck with metallic pad WRT glazing. I could avoid the really steep, bumpy descents that tend to glaze them over but the roads in that area are car-free and quite nice other than that......or I could lose a few Kg.

If the temps are cool and damp, mine squeal like stuck pigs.

Once it is warm and dryer outside, my front brake is fine.

t2p

maybe L05A pads will be better than L03A ?

( L05A replaces L03A - which replaced L02A )

maddog34

try any local auto parts store... or even Walmart, among other sources... Search "anti-squeal brake grease".. it comes in multiple styles.. paste, spray-on cans, and even a wax stick like deodorant.... .hmmm... i wonder if..... maybe... it would smell great, but it would only last a day or so... naw.

apply to the back of the pad... i have some in the garage for when i do car/truck disc brakes... that stuff is orange and the consistency of silicone gasket stuff... use a tiny dab and spread evenly on the back of the pads... we used it in the M/C shops too.

CrimsonEclipse

The above posts suggest new pads, checking alignment, cleaning rotors.
All valid suggestions.

In the event these do not work, might I suggest new rotors, different shape/thickness

Sometimes, a combination of frame/rotor/caliper have a resonance frequency that will not be dampened with any pad selection.

So selection a new rotor is the easiest, followed by new caliper (I will not suggest new frame due to cost and complexity)

deadzone

All this hassle when standard rim brakes work just great with minimal to no maintenance.

Camilo

You'll be accused of hating any current technology

smd4

And being a Luddite.

Ryan_M

Just a follow up... a new rotor fixed the problem instantly. That answers one question, but brings up a few more. I thought in pretty much all cases squealing was caused by contamination, and pads being porous were the usual suspect. I've redressed both the pads and the rotor a few times - weird the rotor was the culprit. Maybe I needed to be more aggressive with the sandpaper, or find the right kind of abrasive. Now that I have a "scrap" rotor to f*** with, I'll try a few more things and report back.

Ryan_M

You're not wrong.... sort of? Discs work awesome, but can have some PITA things to deal with the odd time.

The GF has an older road bike that had a 20+ y.o. 105 groupset on it and was past it's life expectancy so I got her an entire R7000 groupset for Christmas. I have to say I was very impressed with the rim braking with the new gear when I tried it out. However, we were out for a ride a few weeks ago and got caught in some drizzle and her braking went to s***!. Brand new 105 pads on Mavic alloy rims, I could actually hear the loss of braking. She was pretty freaked out by it. Apparently it's even worse with carbon rims I hear. I'm on the fence but seems both have their strengths, pick your poison.