Noonievut

I have new Ultegra R8000 rim brakes on my road bike. A few rides and theyy work fine and sound good in all but braking under high speeds / steep descents. It’s just the rear brake giving me trouble. They’re centred, feel exactly like the front brake, retract nicely from the rim, pads are slightly toed in. Rims are relatively new and clean. I checked torque, lightly sanded the pads, that did not help.

The noise isn’t a squeal, more of a metal sounding shudder/vibration. Bike is steel.

What steps should I go through to diagnose the problem? Or, if I pull the brake off the bike and look it over and then reinstall, what should I check or do as part of installation?

Koyote

Try cleaning the rim, the brake track in particular. Scrub it down with the rough side of a scotchbright kitchen sponge or something like that.

Iride01 

Braking noises rim or disc can just be contamination. I had some rim brakes that squealed for a good month before the contamination or what ever was causing the noise went away.

Any time I spray something near or use a cleaner, soap or lube on my bike, I'll try to soak a towel with rubbing alchohol and clean the brake surface whether it's rim or disc. If I feel that I might have gotten something on the pads, then I'll clean them too.

Many times such noises will go away quickly on their own if you aren't doing something that is regularly contaminating the brakes. Like spraying WD-40 indiscriminately on your chain and cogs. Nothing against WD-40, I use it often. Just not as much anymore on bikes since my kids grew up and quit leaving their bikes in the rain to rust up the freewheels.

Noonievut

already tried that, but thanks

ARider2

I would remove the brake pads and closely inspect for any debris stuck in the pads, or signs of glazing, or ridges. Have you tried swapping the pads front to rear to see if it persists?

Noonievut

Ill try that thanks

ridelikeaturtle

A shudder / vibration makes me think something's either not tightened correctly (the caliper?) or something's cracked or broken and it's not becoming apparent until strong force is applied.

It's dangerous, but if you can safely attempt to observe the brake while it's making this noise, that might shed more light. If you had a camera (e.g. a Cycliq Fly6) you could point at the brake caliper, that'd be interesting.

shelbyfv

I've had a persistent squeal from my rear 8000 brake. I've cleaned everything several times, swapped pads from Shimano to Koolstop and back again. Sanded pads, toed, etc. I'd been using the brakes for over a year before this started. The mounting hardware did not include a serrated washer so I added one. That didn't cure it but there was definite improvement so might be worth a try. FWIW, the front is fine using only the included flat washer and as I said, the rear was OK for a year or more. Next I'm going to try a different wheel. Good luck and please report back if you resolve this.

Noonievut

That's interesting that it was a year before this started. Mine was from ride one. And the same wheels with 105 brakes never did it. Worst case I'll put the rear 105 back on, no biggie. Maybe that 105 brake has a serrated washer so I'll add to my list of steps to resolve. The guy who set them up is great so I don't think it's the set up. He's worked on my bikes for years and no issues. The rim has the slightest out of true wobble (I've had much worse than this).

blamester

So is it dangerous?
Do you need to think before you brake?
Do you have to plan around the issue?
​​​​​If it isn't and you can deal with it let the brakes bed in for a while and see what happens.
There may be nothing wrong at all that time and wear won't fix.
An experienced guy set them up so they are good.

freeranger

Seeing how thorough you've been, you may have already checked, but thought I'd mention it anyway. Have you checked the brake mounting bolt (that goes thru the middle of the fork) for looseness? Seems like that could be a possibility.

shelbyfv

^^^ Yes, that's sort of what I hoping to resolve with the serrated washer. There didn't seem to be any unintended movement in the caliper assembly itself. IIRC even with the mounting nut torqued down it was possible to move the caliper by hand. The washer seemed to help.

freeranger

I just went out to the garage and checked the front caliper on my LeMond (generic brake-no markings on it).. Zero play in the caliper. Seems like play could cause a "shudder". Should be some way to eliminate the play without binding the caliper, or so it would seem! Maybe a flaw in the design of the front brake mounting?

drlogik 

If these are replacement/upgraded brakes, are you sure that the brake caliper spindle is the right length and shimmed properly? The bolt could be tight but the caliper actually a little "loose". Wiggle it back and forth to see if there is any play at all.

The shim pads are important because if the stay bracket is round and you have a flat shim bumping up against it, you're gonna have vibration problems. Or if the flat where the bolts go through is round on the stay bracket but the shim is square, you'll also have problems. Ask me how I know this......

Noonievut

I made some more tweaks and have hopefully resolved the problem.

- I removed the wheel, putting it back in to make sure it was well seated, and that the QR was closed properly
​​- put a couple drops of triflow around the pivots and then cleaned
- the left pad was toed in quite a bit, in such a way that the back of the pad would catch the rim only when lever pulled really tight, I set it to .5mm using a feeler gauge under the pad on the back when tightening
- same pad was also not striking the centre of the rim (wasn’t far off but now centred)
- I wiped the rim clean with rubbing alcohol
- I then tightened the caliper a bit more

I went down the steepest hill in my area and grabbed all back brake...no shudder or noise. This hill isn’t as big as others a little further from home. I’ll know more when I’m next on a longer ride with some steeper and longer hills.