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Loud Rear Brake - Need Help

88bmwjeff

88bmwjeff

SF Bay Area
The bike: 1988 R100 RT
I’ve noticed recently that the rear brake makes an extremely load noise, and I’m trying to figure out where it’s coming from and why. It’s very loud and I can hear it while riding with custom made earplugs that block out most sounds. It almost sounds like a metal-on-metal noise. It’s also a constant sound—not one that pulsates that could indicate an out of round drum. There’s plenty material left on the brake pads, but the pads did seem a bit shiny/polished more than I would expect. I roughed the surface up a bit with a scotch brite pad, but I haven’t had a chance to see if that helped at all. Any suggestions on where to look and/or possible cause?

Thanks in advance
 
Assuming a rear drum, are your brake springs where they belong and installed as designed to be? Is your final drive in good shape? Have you changed the gear oil lately? May be a final drive bearing. Good oil level in the drive shaft? Can you replicate the sound, parked on the center stand while rotating the wheel?
 
Sometimes the brake rotor can develop a hard spot that will exhibit noisy operation. Or it could be corrosion on the rotor. Or even a sticky caliper piston. Ride the bike for a couple miles and see if the rotor gets too hot to touch. It could be any of a few things causing the issue. When was the last time you flushed the brake fluid? What is the condition of the hose?
 
How old are the shoes? The friction material can age out and harden. I've not seen that cause noises but it's certainly a possibility.
 
Let me try this again. I wrote this up midday and thought it was successfully posted; however, it's not there now. So here it goes again.

Thanks for everyone’s comments.

I inadvertently forgot to include two bits of information. First, the bike has about 105,000 miles. Second, I had the rims powder coated. I don’t know if there can be any issues with powder coating process, but I had seen other had done it with no problems noted.

6322, Springs appear to be where they’re supposed to. I believe the final drive is in good condition. I had it rebuilt about 15 years ago and I have only put on about 10-15k since then. Oil was replaced about six months ago. It looks like I may have to try and replicate the noise with the bike on the center stand. However, I’m not sure my experience and knowledge is sufficient to diagnose more than where it’s generally coming from.

ccolwell, the shoes are about 15 years old.
 
ccolwell said:
I'd replace those regardless of whether they cause the noise.
Click to expand...

Looks like I should probably replace the pads and springs just to rule them out (or perhaps, resolve the issue).

FYI, the rubber part is still on the springs (#17 on the parts fiche)
 
Can you be more specific about the noise? Is it a screetch? A pounding sound? Grinding? Squeal?

That might help with the diagnosis.
 
So, I picked up a new set of brake shoes and finally got around to installing them. I didn't have a lot of time today, but I did take the bike for a short 5-10 ride and the rear brake is no longer loud. It does seem like the brake shoes were too old. Which poses a big question. How long to brake shoes last (not miles ridden, but just age of them being installed). It appears that 10-15 years are too old. I didn't think the brake shoe lining would harden that much over time to cause such a loud squeal.
 
Last edited:
If memory serves me right, the rear brake shoes in my /7 are original. Still have a decent amount of thickness. Very little of my miles is around town.
 
88bmwjeff said:
It does seem like the brake shoes were old. Which, poses a big question. How long to brake shoes last (not miles ridden, but just age of them being installed. Clearly 10-15 years was too old.
Click to expand...

I’m am historically not tough on brakes- or clutches. On the question of aging brake friction materials, I have run both caliper pads and shoes to where the adhesive that hold the friction material releases from its holder way before the actual brake material was worn out. There is no way that I know of on how to gauge the life of the adhesive/bonding agent.
I do remember shops “re-lining” shoes (riveted shoes). :gerg
Probably most are replacing shoes and pads due to wear and not age.
OM
 
While I am (at least temporarily) no longer riding older bikes, I think 8-10 yrs is probably a good limit. Shoes/pads aren't cheap but having maximum braking power is priceless.
 
With this being a rear brake, which doesn't see all that much use compared to the front, I think it could be given a longer time of service. I really only use my /7 rear for trail braking and mild use when coming to stops...lots of front brake which I have replaced pads/pistons over the years.
 
Mine

I went nearly 200K miles on my rear shoes on my 84 R80RT. Sadly when I had to finally replace the shoes, I also had a worn wheel that needed to be replaced. One of the negatives I have with BMW, a drum can't be replaced separately from the wheel on snowflakes. St.
 
Back in the '80s I was riding a then 10 year old R60/5. I found the brakes to be horrible. With advice from Oak Okleshen I meticulously followed the procedure to correctly adjust the front brake. The brakes were still horrible. Smokey Yunnick in Popular Mechanics or Popular Science had written a few bits about brakes, including a few paragraphs about the hardening of aging brake shoe lining material.

I decided to have the brake shoes on that /5 relined with new friction material at a brake specialist in Kansas City. The new material transformed those brakes from horrible to good. They put to shame the brakes on my next bike - BMW's original anti-lock brakes - the single front disk on an R75/6.

It is my opinion that old brake shoe lining material hardens over time and loses some of its coeefient of friction. That opinion comes from some faintly remembered old magazine articles and an anecdotal case study of one - two if you count both wheels. YMMV
 
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