Rear Brake Pads Rubbing Against Rotor

[stokes776]

It seems like my rear brake pads are rubbing against the rear rotor constantly.  If I put the bike on the center stand and try to rotate the wheel I dont get a single rotation out of it, it stops pretty quickly as soon as I stop moving it with my hand.

I recently had a new tire put on the wheel, and removed the wheel/remounted the wheel myself.  I also checked the brake pads for the first time, not knowing what a bad brake pad looked like (and not having a working camera to take a pic).

Last night I took the brake pads out again and took some pictures (sorry about lack of focus, phone not 100%), which after researching pads, I am a little scared to post, as they look extremely worn.

I tried pushing the pistons back in, remounting the pads, and then pressing on the brake lever, but they are still rubbing against the rotor at low speeds.  The thing is, riding wise, I dont really notice it at all except a... 'bad noise' coming from the rear brakes when I come to a stop, enough to make me check them.

1. Pretty sure I need to replace these ASAP?
2. Once I get new pads in, will the new ones rub against the rotor? Is that normal?
3. If not normal, how do I adjust so they dont rub against the rotor?
4. I havent checked the front yet, do front pads wear faster/slower than rear? I assume this depends on x,y,z, but just in general?

Bike is only a month in my possession, so I swear I did not do all of this! Just doing all the maintenance the PO did not seem to do!

[BrianKD]

How far were you able to push the pistons in? You should be able to push them in past the caliper walls.

If they fight you, take the cover off the rear brake fluid reservoir. This will relive pressure on the pistons and allow you to push them in further.

[stokes776]

I only pushed them back a bit, not all the way. Then I put the pads in, they were not rubbing, manipulated the lever a few times and then they were rubbing again.

Do I need to push the piston ALL the way back to 'reset' it?

This might be too deep of a question, but I dont quite understand how the system is able to calibrate itself to get the pads close enough to allow for braking but not close enough to rub.  That is, it seems like once the pistons come OUT, they don't go back IN very much at all.  When I activate the brake lever, they come out more (enough to fully brake the wheel) and then go back in so the wheel can rotate, so that parts works.

[jestercinti]

What you describe can be caused by one or all of the following:

Alignment of the rear wheel.
Brake fluid.  If it looks like used motor oil, flush and fill.
Air in line causing the piston not to retract.
EDIT:  One more thing I forgot to mention is a bad caliper.  That should be your last resort though.

I recently had my rear tire replaced by a shop (was stranded far from home), and noticed that it was driving funny.  Wheel alignment was off and the brake pads were rubbing exactly how you describe.  I fixed the alignment myself, and all is well.  The wheel spins many turns now before stopping via the chain tension/friction (meaning normal).

It's frustrating, but take a look at my 3 suggestions above.  Again, one or all of the above could cause your issue.

[BrianKD]

+1 on the miss-aligned wheel!

A miss-aligned wheel means the brake disk is also miss-aligned. If the brake disk is spinning inside the brake caliper at a slight angle, it will drag on the pads in the manner you describe.

I had the same problem. Here's a video of the problem and how to fix it. It's on the FRONT wheel, but the principle is the same.
http://www.youtube.com/watch?v=OBEkhVW7dGY

Do I need to push the piston ALL the way back to 'reset' it?

No. Piston's don't "reset". You just need to get those pistons far enough back for you to drop the pads in without FORCING them in.

This might be too deep of a question, but I dont quite understand how the system is able to calibrate itself to get the pads close enough to allow for braking but not close enough to rub.  That is, it seems like once the pistons come OUT, they don't go back IN very much at all.  When I activate the brake lever, they come out more (enough to fully brake the wheel) and then go back in so the wheel can rotate, so that parts works.

The "braking system" on a GS500 doesn't really calibrate. It's just a glorified one of these:


The pistons never go back in when you press on the brake. There is no spring to pull them back, nor is there enough suction from the brake line to suck them back. They only release their grip on the disk.

[stokes776]

Thanks guys, I will check the alignment of that rear wheel.  When I took the wheel off and remounted it, the far end of the alignment adjuster thingy just spin around and got bent when I was torquing that Castle Nut on the axle.

I am going to watch a video shortly, but I suspect I check the alignment by tightening or loosening those nuts on the end of the swing arm.

[jestercinti]

That same thing happened to me (bent alignment metal). You can take it off and bend back or pound flat with a hammer.  If that fails, you can order a new one.  They are only a few bucks.

[stokes776]

Well I spent about two hours trying to adjust it before I realized you need to tug on the wheel once you adjust the little 12mm nuts, in order to reset the axle to the new location. I had been doing it unintentionally before I think I started to understand how it actually works.

I took the brake pads off and put them back on again. Same extremely worn set, new set should be in on Friday.

Once I got it adjusted it seemed to be rubbing less, maybe an improvement.  Got on and rode it for about an hour and no problems, except when using that rear brake coming to a stop I can just feel it grinding/biting.  Cant wait for the new pads.

My question is, once I put the new pads on will it still do this, where the pads are seemingly too close to the rotor?

[BrianKD]

My question is, once I put the new pads on will it still do this, where the pads are seemingly too close to the rotor?

Yes. If worn pads are rubbing. New thick pads will rub even more. You need to find out what's hogging all the space in between the pads and the disk.

[MarkB]

It's fuzzy, but looking at the second photo in the original post, it looks like the brake pad surface is pretty much gone and you're getting metal on metal between the backing plate and the rotor.  That would explain the nasty sounds and feeling like it's grinding (because it is).  You clearly need new pads.

The brake pad doesn't retract much from the rotor in normal operation.  When you have the new pads in, you should of course ride it to verify that the brakes provide sufficient stopping power.  Your second check is to ride for a bit without using the rear brake then get off and feel the rotor.  If it's cool to the touch then the pads are not dragging.

If the rotor is warm and you're sure you've got everything assembled and aligned correctly, you may have to clean or rebuild the brake calipers, but I'd bet that new pads alone are going to solve your problem.

[stokes776]

Alright, the pads came in a day early (wohoo!) went and picked them up and installed them last night and took it for a ride.

There was some initial funny noises.  Maybe it was just in my head but I swear I could hear something rubbing or not right just going down the road in first gear with the new pads on, and it seemed as though the faster I went, the more pronounced it got, but I couldn't tell for sure because of the wind noise. I am thinking this was just the 'bed in' period.

I rode the bike for about 10 miles, using the rear brake generously, and as someone else had mentioned (possibly in a different thread) gently pressing on the rear brake for a few seconds while going down a street.  As I was coming back from my ride even though they felt better, definitely better braking performance, I still couldn't shake from my mind the idea that the bike was working harder to propel me down the road, almost as if the brakes were still dragging a bit.

This morning, with a clearer head than last night, I rolled her out from the garage and instantly noticed the improvement, with engine off, walking the bike in neutral there was no drag on the rear wheel.  Prior to the brake pad change there was LOTS (less after the wheel alignment) of drag and noise on the rear wheel just walking the bike around in neutral with the engine off, now there is none.

I suspect I just need to tweak the alignment just a teeny bit more, I went out and got some string to try that to align the wheel (tried the laser level, didn't like it) although I am worried about making perfect the enemy of good enough.

I think this is pretty much resolved, but I will update once more after I align again, just in case anyone in the future needs to reference this! I myself hate finding posts where the fix for the problem is not detailed and explained!

[BrianKD]

How many revolutions do you get when you spin the rear wheel? You should get two if everything is lined up right.

[stokes776]

Two rotations sounds 'about' right for what I was getting, but I will need to go out and check.  Me over-thinking it would ask, how hard to rotate the wheel, but I will just give it a good heave and see if I get two rotations.

Also, just to be explicit in everything I did, I did pick up a brake bleeder kit, (bottle + tube_ brake fluid and brake cleaner.  When I had the bad pads out I sprayed some brake cleaner at the pistons while they were nearly fully extended, and used a toothbrush to scrub on them just a bit, I could really only get the tops of the pistons but my hope is that its better than nothing. As I pushed the pistons back in (had to remove some fluid to get them all the way back in) I sprayed a bit more brake cleaner and scrubbed a bit more with the toothbrush.  I don't know if that's the right way or the wrong way, but the brush came out looking mighty grungy, and the brakes seem to be working just fine now.

Thanks guys, will keep updated!