Rear brake pad question

[Lucien Harpress]

I've got a nagging issue with my rear brake caliper- somewhere I've got a brake pad rubbing, which eventually heats the whole rear brake system up enough to lock it up. I'm just wondering if it's an issue with the brake pads.

How much "play" should there be with the brake pads? Should they slide back and forth on the tracks relatively easily, or not? As of right now it's a bit of a pain to get in, and you have to pry them off to get them out. I'm just wondering if when I use my back brake the pads get stuck enough to rub on the disk.

Thanks for the help.

[DGXSER]

My guess is you have an air issue more so than a brake pad issue.

I used to have an XS750 with a broken bleeder. Back in my younger but stupid days. I rode it anyway with air in the system. After so long, it would lock up. Caused me to dump the bike a few times when I started slowing down and the front brake grabbed hard.

[CatatonicBug]

You should be able to spin the rear wheel by hand with almost no resisance. Do you have enough free-play at the brake pedal? The pedal should be able to go down something like 1/4" before making contact with the master cylinder.

If nothing else, it may be worth taking the caliper and master cylinder apart and cleaning them. It should only take 2 hours max to take it all apart, clean and reassemble, and bleed the system. It'll only cost a few ounces of brake fluid too. Concentrate on the grooves UNDER the rubber seals, and the spooge hole in the master cylinder. Be sure to lubricate the pin that the pads slide on too.

[draketrumpet]

Originally Posted by CatatonicBug

You should be able to spin the rear wheel by hand with almost no resisance. Do you have enough free-play at the brake pedal? The pedal should be able to go down something like 1/4" before making contact with the master cylinder.

If nothing else, it may be worth taking the caliper and master cylinder apart and cleaning them. It should only take 2 hours max to take it all apart, clean and reassemble, and bleed the system. It'll only cost a few ounces of brake fluid too. Concentrate on the grooves UNDER the rubber seals, and the spooge hole in the master cylinder. Be sure to lubricate the pin that the pads slide on too.

If you have trouble trying to bleed after this, you may need to rebuild your rear MC, or at least clean the rod in it really well. There are 3 or 4 small holes on a plate in the middle of the rod that were plugged on mine that didn't allow it to bleed properly. I was having a similar issue, rubbing, locking after a bit. We cleaned the whole system 3 times before it worked right. Mandatory triple clean isn't only for carbs

[Lucien Harpress]

I've been through the whole rear brake system already- needed to clean it out after I bought it; the rear brake was completely locked up.

A bit of air in the brake lines is a possibility- I did bleed it, but I've heard how hard these are to bleed right.

HOPEFULLY all I'll need to do is oil the pads. Again, I had no clue how much they were supposed to move. They were pretty gummed up, and (as I said) are pretty tight on the caliper. I"ll give 'em a shot of oil, and see if that fixes the problem.

[Rasputin]

Do NOT under any circumstances use OIL on your brake parts! Oil on Brakes can really ruin your day! Re-read CBugs post and do some checking on your adjustments and bleed the brake again to ensure any air is out of the system.

[CatatonicBug]

Originally Posted by Rasputin

Do NOT under any circumstances use OIL on your brake parts! Oil on Brakes can really ruin your day! Re-read CBugs post and do some checking on your adjustments and bleed the brake again to ensure any air is out of the system.

Yeah... Oil isn't a good idea. I'm assuming/hoping you meant you're going to oil the pin the pads are held in with, but grease is probably a better idea than oil.

[petejw]

not sure what you meant by oil on the pads,
but NEVER put anything on the pads themselves,
unless its brake cleaner.

have you got the right adjustment with the push rod?
theres a spooge hole in the rear master cylinder
did you clean that hole out well.

the wheel should spin freely with a slight drag
on the pads and rotor.

[Lucien Harpress]

Yeah, so maybe "oil" wasn't the best word to use. I'm HOPEFULLY smart enough to know that anything on the actual brake pad that can also serve as a lubricant is a BAD idea. What I meant were just the pins/tracks that each pad slides on.

I've got the rear caliper removed (sort of- as much as you can get off without having to remove the rear axle), so I'm going to have to re-bleed the system anyway. Hopefully between the two, I'll get this issue taken care of.

I REALLY don't want to have to go through the system again. Ever since I've gotten the bike I've had to:

-Clean it
-Un-freeze the rear caliper
-Rebuild the MC
-Rebuild the caliper
-REPLACE the MC
-Fix the brake light switch
-Bleed the whole system EACH TIME.

Ug. Oh, well. Thanks for the help.

[Rasputin]

I was pretty sure you knew not to use oil on brake parts but many readers and lurkers here may not! I have found that using anti-seize on the parts that supposed to move on brakes works well. You may want to give that a try.

[Ken Talbot]

Originally Posted by Lucien Harpress

Yeah, so maybe "oil" wasn't the best word to use. I'm HOPEFULLY smart enough to know that anything on the actual brake pad that can also serve as a lubricant is a BAD idea. What I meant were just the pins/tracks that each pad slides on..

You're on the right track. What you want to use on the pins/tracks is a silicone based product called disk brake lubricant. It comes in a squeeze tube like toothpaste. A tube will last you for years.