I took my '72 Supreme out for a drive today down some back country twisty turny roads. I stopped for about 5 minutes to enjoy the scenery, and when I went to get going, she wouldn't move. At first I thought it was a transmission issue, but I could feel it go into gear. So after some quick thinking, I realized my rear brakes were locked up. After about 5 minutes more, they finally released and I was back on the road with no issues whatsoever. When I got home, I checked the temp of both rear drums and the driver side was about 475 deg, passenger side was about 275 deg. From the research I've done, it seems it's normal for drum temp to get as hot as 500 deg in normal driving. My question is, why was the passenger side so much cooler than the driver side, and is it an adjustment issue on the driver side? Again, no driveability issues whatsoever, and ambient temp is 75 deg. Oh, and the front brake temp was fine on both sides.

 

Sounds like your driver's side rear brake is adjusted too tight and is dragging when your foot is off the brake.

 

That's what I thought too, but wouldn't I notice it dragging while I'm driving? At any rate, I made a small adjustment to the driver side. Just to clarify, the drum doesn't bind up when taking it off or putting it on.

 

At the very least, go to an empty parking lot, drive the car in Reverse at about 30 mph and slam on the brakes. Do this at least 5 or 6 times. This will get the adjusters in the rear drums to set the drums properly.

 

So it's kinda tough to check for drag by spinning the tire when you've got a posi since there's an inherent amount of resistance anyway. The best I could do was lift both rears off the ground and give both wheels a spin with the same amount of force. I got about 1/4 turn on both and very little drag. Hopefully I'm good, but will know for sure when I take it out again. For now I'm done.

 

You replaced the rear brake shoes last year and only had a handful of miles on them. The brake shoes have not had enough wear on them to "arc-in". A term I learned from my ol' timer mechanic Dad. The outside diameter of the brake shoes is not an exact match to the inside diameter of the brake drums. This will cause them to generate a great deal of heat without the benefit of full braking power. This probably lead to the extra heat and caused the brake pade to stick to the drums momentarilly. After a few more miles and lots of braking they should be a perfect outside to inside match and you will have maximum braking power on the rear but no drag when the brake pedal is released.

 

Ohhhh....that makes sense.

 

I took it out for a run and checked the temp of both rear drums...still got a difference. As soon as I got back home I checked. Driver was around 540 and passenger was around 220. The driver side cooled down to about 400 after about 5 minutes and passenger side was about 200 after 5 minutes. Should I just let it be and keep letting the driver side arc in. Brakes work good, and no lock up after sitting.

 

Are both sides assembled properly with the correct parts... shoes and hardware?
Is the primary (shorter) shoe towards the front of the car on both sides? If reversed the shoes will bind on the drum.

Observing the problem side shoes, what do the witness marks look like as compared to the good side? Full or partial shoe contact? You will always have a little non-contact at the very ends.

If you were to bleed the rears do you get the same stream of fluid out of both cylinders? (possible lazy return on one side due to bad or improperly installed hardware or a bad cylinder)

Has the rear system been serviced with new hardware and greased lately? (possible lazy return on one side)

What about the flex line on the axle to frame? New or old?

 

Here's some pics of the driver side after I put everything back together.

 

Ha Ha! I see your problem. You have two rear shoes on the same side. The two shoes are identical. They shouldn't be. I'll bet if you pulled off the other side drum and looked, the two shoes would be smaller and identical.

Here's a photo of the rear brake, driver side, on my '73 Delta 88 after I redid them. The front of the car is to the left. Note that the front shoe pad is shorter than the rear shoe pad. I've made this mistake before in doing a brake job.

You need to remove the rear shoe on the other side and put in place of the front shoe on the driver's side, and then put the shoe from the driver's side onto the rear of the other side.

 

Just for yuks, here's the passenger side brake. The front of the car is to the right. Note how the front shoe is shorter in length (goes less far around the circumference) than the rear shoe.

 

I think baby needs a new pair of shoes. They don't look like the ones I see in the CSM.

Edit: or what Jaunty said.

 

If the dragging is slight (and it only needs to be that way to generate significant heat), you would be unlikely to notice. Especially on the rear. Drag on one side of the front brakes is MUCH more noticeable since it results in forces that try to pull the steering on one direction. Drums that hang up on removal are usually worn. Fresh or recently turned drums won't do that necessarily. Heat results in expansion and in turn binding, cooling allows things to shrink up and not drag as much. I'll assume you are not attempting to handle hot drums.

Another thing to check is the E-brake cables, make sure they are releasing fully and not binding on one side.

As noted above, same length friction material on both shoes is suspicious. Follow that lead.

 

I'll check it, but how would that cause the problem?

 

Here's the diagram out of the '73 chassis manual. I'm guessing '72 is the same. The front of the car is to the left, so this is the driver's side. The shorter lining, or "primary shoe," is to the front. The longer lining, or "secondary shoe," is to the rear.

 

First of all, you wouldn't get equal braking power from each side. Secondly, you have too much brake shoe area on the driver's side, and the system can't adjust to compensate for it. So you're getting too much frictional heating, which is why that side is so much hotter than the other side and why it even locked up on you once. I would fix the problem right away. If it didn't matter where you put the shoes, they wouldn't make them two different sizes.

 

Well it looks like I got some work to do...here are both sides as of now...
Driver side

Passenger side

 

Yup. You have two front shoes on the passenger side and two rear shoes on the driver's side. I wouldn't drive the car any distance until it's fixed.

 

That's the plan. Will update once I'm done
I won't need new shoes, will I?

 

I would think not. Your shoes still look practically new.

 

Thanks, that's good to know If I don't rotate the adjusters, the adjustment should be ok? My braking feels really good right now.

 

I would loosen the adjusters enough to allow the brakes to self-adjust. About the only way to get equal brake force on both sides. Follow your repairs by doing what Olds64 suggested (back-and-forth stopping hard-ish from 20-30 MPH multiple times until they are acting right).

 

If the shorter shoes are on the driver's side, wouldn't that generate less frictional heating? (Just trying to understand)

 

You have the LONGER shoes on the driver side. That's why that's the hotter side.

 

When I install new shoes, I set the adjusters so that the drum just comfortably slides on and off. A little bit of drag is ok, but the wheel should turn freely. Doing the back up and apply the brakes procedure should get them properly adjusted. In fact, you probably don't have to make any special effort. Just routine driving, which always involves occasionally putting the car in reverse, should be enough to get them and keep them adjusted. The adjusters should keep things properly adjusted for the life of the shoes. At least, that's the idea.

 

This is why I always pull both drums, but only disassemble one side.
Use the other side as a guide to make sure I got it right. Keeps the springs and shoes in the right order.

Get new high-quality USA made hardware kits with new adjusters. Apply antizeise to the adjuster threads and to the heads of the anchor pins.
Put high-temperature grease on the backing plates, on the three spots where the shoe shells make contact with the rub plates.

 

I got my pictures mixed up...this is the driver's side...shorter shoes

Passenger side...longer shoes

 

Preach!

 

Exactly.

And, w/ these new fandangled mobile phones taking pictures prior to disassembly removes the guess work.

 

Hind sight 20/20 The Choir preach's

Thanks for sharing the learn

 

Jaunty75, look at my post #28...shorter shoes are actually on the driver's side.

 

Have you put the short lining (primary) on the front & the long lining (secondary) on the rear on both sides, yet? The braking should be good and I'd suspect equal heat ranges both sides?

 

I haven't yet Norm, but soon. I'm just trying to understand why the driver's side with the (incorrectly installed) shorter lined shoes would generate more heat than the passenger side with the (incorrectly installed) longer lined shoes. Seems to me logic would dictate that the passenger side would generate more heat, or am I missing something with the law of physics in general?

 

I missed that. I was looking at your earlier post. Regardless, you have to fix the problem. You have two long shoes on one side and two short shoes on the other. The physics of the situation makes the shorter shoe side get hotter. Maybe because the smaller shoe area on that gives less surface for the heat of friction to dissipate over. I don't know exactly. It doesn't matter. You still have a problem that needs to be corrected and that very likely accounts for the temperature difference you measured and the wheel lockup.

 

Ah, OK, Dave. My take on the short-lining (primary) front & long-lining (secondary) rear is to accommodate the self adjusters which are designed to provide (I assume) appropriate adjustment to both short-lining & long-lining when installed in the correct locations (orientation)?

 

Hmmm...that makes sense to me. I'll be taking care of it this week.

 

Remember, the goal here is to fix the brakes. You can worry about submitting an article to the Journal of Friction and Wear later.

 

LOL...copy.