rear brake suddenly screeching like Tarzan

pagheca

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Canary Islands, Spain
All of a sudden, today the rear brake on my ebike started squealing REALLY REALLY loudly! An embarassing sound resembling that of a Johnny Weismuller yelling that would wake dogs and birds up 3 miles away... :eek:

The pads were changed a hundred miles ago by a service center. Do you think It is better to take it back to the shop or do I do it myself, take it apart, clean it, and put it back together?

 
bent rotor? anything stuck between the rotor and pads?

they do make some crazy noises :ROFLMAO:
 
This is going to sound bad but it is really meant with friendship and support.
While “changing the brake pads” sounds simple it is actually one of the most finicky maintenance items on a bike.
Even the simplest of V-brakes or cantilevers can be frustrating and difficult to do correctly.
Disc brakes are an entirely different level of complexity. While seemingly more simple to accomplish, they are fraught with opportunities to screw up and create lasting problems.
The fact that you ask this question leads me to suggest that you may be better off letting the shop handle it.
Having said that getting the tools you need and building the skills to accomplish regular repairs like this will make your life easier and greatly improve your enjoyment in cycling.
If you have a friend who is actually good at things like this (as opposed to someone who just does it) it would be worth the investment of a few beers or a couple of smoothies to get them to mentor you and teach you how to do it properly.
Failing that some community colleges and even bike shops have classes in bike maintenance that can help.
Having a good tech gives you confidence that the job is done right but that doesn’t help much when you are ten miles out on a trail and something goes wrong.
 
thank you all for the suggestions! :) I removed the pads, cleaned and check them... Nothing unusual except I noticed one of the pad was worn not completely tangencially, but I do not think this is the problem.

I will test it tomorrow...
 
thank you all for the suggestions! :) I removed the pads, cleaned and check them... Nothing unusual except I noticed one of the pad was worn not completely tangencially, but I do not think this is the problem.

I will test it tomorrow...

Sometimes even after an adjustment, the caliper will scoot over one way or the other for some odd reason or another.

I had a rock get caught in my caliper somehow and it made a terrible screach and even moved my caliper.

Good catch before it was to late!
 
One quite helpful thing to try,after you clean things well is try loosening the (usually) two bolts that hold the calliper together than fully apply thebrake, and whilestll holding the brake on, tighten the bolts back up. That will help center the caliper on the rotor, regardless of pad wear. On my bike the difference was considerable and noise gone.
 
the screech is vibration,perhaps some anti screech grease between the caliper and pad would help,had one bike with a hundred db screech after i changed pads,still screeching when i got rid of it,however i liked the racket to scare the deer away from the road slamming into a whitetail at close to 40 mph doesnt seem like a good career move.
 
I have extensive mechanic experience and I obviously know about using grease lubricant
you use that stuff on what? The rotor or pads?
or do ya mean like moving parts on a mechanical set of bike brakes?

I'm a bit cornfused here o_O
 
the screech is vibration,perhaps some anti screech grease between the caliper and pad would help,had one bike with a hundred db screech after i changed pads,still screeching when i got rid of it,however i liked the racket to scare the deer away from the road slamming into a whitetail at close to 40 mph doesnt seem like a good career move.

I've also used that Aluminium tape for heating and cooling...
small patch placed onto the face of the pistons then the back of the pad then reassemble and screech gone and never came back.
 
put a small amount between the pad and caliper any noise is just a vibration no vibration no noise.never put any gunk on the rotor
 
No luck: I also tried removing the rear rack in case it was stressing the fork (unlikely), but nothing changed :banghead: . I think it is probably related to something I did time ago (and forgot about): I came home very dirty and just cleaned the wheels with water. Then I went on a trip for a month or so. I suspect that the problem developed right after that wash.

At this point I will take the bike to the shop. I do not want to fiddle with the brake too much... Roads are too steep here to accept any risk of failure.

Anyway, thanks for all the suggestions, guys. :)
 
I think it is probably related to something I did time ago: I came home very dirty and just cleaned the wheels with water.
BOOM there's your problem.

You un-bedded your brakes. Before I read this, I was going to post that you should do nothing, that your situation sounds exactly like any of my bikes after I have been out riding in the rain, because water splooshing over and onto the rotors removes the bedded pad compound that is invisibly coating your rotors. So for at least a short time you get screeching and vibration as the pads run against the bare metal.

Solution is to bed your brakes. If you live in steep hills like I do, the screeching and vibration goes away by the time you get to the bottom of the first hill. But if you are doing more gentle braking on say flat land, it can take a while to go away in normal use because you aren't getting the pads up to high temp.

So... do this.

 
I see... thanks for the advice @m@Robertson! I didn't know about that. There is NO flat land around here, so it should be easy to fix: I will go up and down the road bringing up to my house as suggested in the article and see what happens. (y)
 
I see... thanks for the advice @m@Robertson! I didn't know about that. There is NO flat land around here, so it should be easy to fix: I will go up and down the road bringing up to my house as suggested in the article and see what happens. (y)
In that article a quickee bed is described for going down a hill. Thats what I use after a rainstorm.
 
I had an intermittent squeaking noise from my front brake while riding that if applied the front brake momentarily would stop the squeak for awhile. It started happening more often so I finally decided to check it out. This is on a mechanical disc brake setup. On my setup the inboard pad is fixed while the outboard pad moves in to apply pressure. While applying the brake I noticed that it was pushing the disk toward the wheel about .100 / 2.54 mm., not good.
I checked the disk / rotor for run out and there was none. Took the caliper off and everything looked good. I did notice that the screws had been installed with blue loctite from the factory. When I put it back together I adjusted the caliber / bracket to have a gap between the inboard pad and disc of about .0015 / 0.0381 mm. The outboard pad has a gap of .010 / 0.254 mm. The brake works great with no noise. Because I can I decided to safety wire the caliper mounting screws.
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