Rear Drum Brakes Grabbing
 

Here is the deal, I have new fron Disc brakes, New master cylinder and Booster, New Rear Brake Shoes and slave cylinders on both. They all bleed and flow easily, Long linings in rear and shorts in front of both sides, correct adjusters on the correct sides, however on my passenger side after a while driving and it self adjusting only that side get to tight and starts grabbing or I should say braking. Make me feel like I'm towing the qween mary. Put it up on lift and can turn it by hand in reverse but not forward. I have also welded up the six rub pads on the backing plates and resurfaced then as they did have bad grooves. Emergency cables have been disconnected and or loosened with no changes. With Drum off the axle moves freely so bearing is good and there are no leakes. Drums have been checked for out of round and are good. All Springs are new and in great shape. What else is there?

Has anyone ever got a bad set of shoes, or does anyone else have any ideas?

Re: Rear Drum Brakes Grabbing
 

Is this the way it was before you replaced all the brake parts in the rear? Meaning no change? If you back off the self adjuster and drive a while, does it tighten back up?

I would not think its a shoe issue, but maybe its a fluid flow issue, not returning to the MC. I have had rubber brake lines on the front collapse and would not allow fluid to return to the MC.. The rear is all steel lines except for the one flex line.. I would also look at replacing that flex line in the rear too.

Re: Rear Drum Brakes Grabbing
 

You sure that self-adjuster is not in backward on that side that is grabbing?
Here's the way it should look. http://repairguide.autozone.com/znet...3f8020d779.gif

Re: Rear Drum Brakes Grabbing
 

I was wondering that too.

Re: Rear Drum Brakes Grabbing
 

Strange, esp. with all the conditions you described! One thing you said would make me suspicious: "I have also welded up the six rub pads on the backing plates and resurfaced...". The actual separating of the shoes is what makes the adjusters work--little movement while separating(while braking)means little self-adjusting going on; and vice versa. I'd think if there were any binding that limits separating on the DRIVER SIDE, then it would receive LESS adjusting, while PASS SIDE would receive MORE adjusting. Maybe time for new backing plates? Just theory, no actual experiencing it.
You could swap sides w/shoes & try it if you suspect bad shoes--that should make problem switch sides.
If all else fails, one could always alter the system to "render the adjusters inoperative"--I never suggested to remove the self-adj. system, did I?
Sam

Re: Rear Drum Brakes Grabbing
 

After further thinking, I agree with what others have said: it does not sound like a shoe problem, but more like fluid-flow. Next time it tightens up, see if opening the bleed screw frees up that wheel. (then try loosening the line at the cylinder; then loosen the line at the tee.) If this frees it up, it's either a bad wheel cylinder or the fluid line from the cylinder to the "tee". If it was a bad flex line, both wheels would tighten up.
Sam

Re: Rear Drum Brakes Grabbing
 

As stupid as this may sound, I put the rear shoes on backward and they grabbed jusy like you saying. I learned that one shoe is a touch longer than the other and needs to go on in the correct location.

You sure you got that one correct?

Re: Rear Drum Brakes Grabbing
 

Here I am thinking out loud again. There should be no way a self-adjuster could adjust too tightly........unless something like the drum being too thin, expands when hot, and the adjuster tightening the shoe while the drum is expanded; then, when drum cools off, the shoe will be too tight.

Check the e-brake bars to ensure they are seated in the correct slots of the shoes, esp. the one on the good(driver's) side.

Please, could you post a pic of each side with the drum off? We all should be able to offer more informed opinions as well as answer ???? you have already answered. Plus, we will feel more comfy that your descriptions are accurate and that your pics look like ours do when our systems are working correctly.

Sam

Re: Rear Drum Brakes Grabbing
 

Yes it does tighten back up after I back off the adjuster. after a couple of days of reverse stops. Brake lines in front are new along with the Disc brake convertion,. rear single hose looks fine and lets fluid return for the other rear whell just fine and like I mentioned the flow seemed good when bleeding as well as reverse bleeding with my Phoenix DIY, I have to go slow or there is a geiser under the hood at the MC.

It seems like the slave cylinders ar not good but they have now been replaced with brand new ones, and I checked the new ones for smooth operation.

When I take the drums off the shoes arn't fully returned and seated on the top capstand pivot point. But like I said the springs are all new and the shoe rub points on the backing plate are smooth and greased lightly with lithium.

I do brakes all the time but this one has me stumped.

Re: Rear Drum Brakes Grabbing
 

Obviously, I wanna see what fixes this. You said, "I do brakes all the time but this one has me stumped." Also, "When I take the drums off the shoes arn't fully returned and seated on the top capstand pivot point." I'd like to know: (1-A)ARE you talking about 2 shoes(pass only) or 4 shoes(pass AND driver side?) (1-B))This 2nd quote doesn't sound right to me; does it to you? If not, why do you think they do not return? Answer: Something's wrong. (2)Gotta be either mechanical obstruction or fluid obstruction, do you agree? (Reason: [a]The springs, mechanical, should return them to flush against the pivot, if mech'l parts are assembled correctly, right?...and[b] The release of brake fluid pressure, fluid, should allow pistons in cylinder to retract which allows shoes to retract, right?) (3)If fluid problem, it is isolated to passenger side, correct? (You said the driver side is free from this problem.) (4)If so, it's gotta be wheel cylinder or cylinder-line from tee to that cylinder, right? (After all, the other side does not have that obstruction, right?)

Are you sure driver side shoes have returned to capstan pivot and seated, when the pass side have not? (5)NOW, If both sides are unseated and not returned to pivot point, then a bad flex line could be the culprit--even tho' the driver side has not self-adjusted up tight yet, right? (This could be just that pass side has heated faster due to shoes rubbing on drum a tad earlier and locking pass shoe up FIRST due to 'shoes dragging' more or sooner than on driver side.)

We still would like to see pics with drums removed. Remember, we all love pictures on this forum.:lol:

Looking forward to seeing this one through. Don't forget: I too now have a lot(of time) invested; so I feel deserved to being kept aware of the progress--good AND not-so-good--as well as the final solution.
...and now your partner!;)
Sam

Re: Rear Drum Brakes Grabbing
 

Did you change the master cylinder with your disc conversion up front? I believe that master cylinder for discs use a check valve to keep pressure on the calipers vs. drums which do not use the check valve. Would be interested if you have a master cylinder that is for discs all the way around vs. disc on front drums on the back?
Regards,
Steve

Re: Rear Drum Brakes Grabbing
 

This.
I did it on my Suburban, and didn't figure it out for months.

And thousands of miles.
The shoes would grab and drag, the brake fluid would get hot, and pretty soon I'd have a rock-hard pedal.
I'd pull over, bust out the tools, un-screw the self-adjuster in a parking lot, and go until the self-adjuster tightened the shoes up again, a few hundred miles or several weeks later, depending on how much I backed up in that time (activating the self-adjuster).

Once I realized what an idiot I was, that particular problem was solved.

-Brad