Drum brake dragging.

[Jimflorida]

I have rebuilt the drum brakes on the rear of my BE. All new parts, drums, etc. (it has the disc and drums from a later model and wire wheel hubs.) On one side, when I tighten the bolts up on the drum, it spins fine until It tight, and then I can't even turn the drum. I have the adjuster turned all the way out, it is not dragging on the backing plate anywhere I can see, and the shoes seem to be centered where they belong. Any ideas? Jim

 

[jlaird]

Obviously, and not trying to be funny, the shoes are too big.

Are they new drums?

Really need to have the shoes cut down a bit. I had to do that with Miss Agatha, all the shoes and I tried three sets were just a bit too big.

Use to turn the shoes after riveting the new linings on all the time. I have a friend who does Model A and Ts so he had a thing to do the job. Very old school.

 

[Jim_Gruber]

Jack,

Are you talking about trimming the leading and trailing edges? Angle grinder, hand file, worries about asbestos dust? This sounds like lore information needed or is there a recommended rear show that fits properly to correct specs. Now you've got me curious.

 

[Jimflorida]

Thanks for the ideas. It is a mystery to me. I have refitted the shoes several times just to make sure they are correct, and have the adjustor all of the way out. The drum will turn fairly freely until that last turn of the wrench on the nuts. I don't know where it may be binding, and I can't really see any marks on the shoes or drums where it may be dragging.

 

[Billm]

Jim
After you tighten the shoes and the drum stops turning do you push the brake peddle really hard a couple of times? Usually this will help center the shoes and allow you to tighten them some more (and you push the peddle in between adjustments each time until it is correct).
BillM

 

[jlaird]

No. the machine thing actually trims the linings in a curve to match the drum.

 

[Sarastro]

Trimming the brake linings was a fairly common thing to do back in the medieval period when these cars were new. It was done to all kinds of cars, not just LBCs.

Try BillM's suggestion first, but if you can't make it fit that way, just shave off a little of the lining with sandpaper or a file; there will be marks on the shoe surface showing where it's rubbing. Wear a respirator and hazmat suit, of course....

 

[Deleted member 8987]

Arrrrr....maybe not. If the drum turn fine until the last bolt is tightened, I would think the backing plate is hold the shoes too far out.....not in an "apply" direction but rather out towards the lug nuts.
Seen it before. I would be taking a dial caliper and measuring all 4 shoes to see if one is to wide, and to see if one is glued on too far "out". Look closely at the inside of the drum, at the part just 90 degrees off the machined friction area.
The look at the backing plate in the area between where the lining would be and the outer edge of the backing plate for drag marks.

Next, I would try the drum without any shoes at all, just to be absolutely certain it's not a drum/backing plate interference.

Any chance you mixed drums left to right? One may be slightly different (on an LBC? Oh, my...) and touching.

Just the troubleshooting I'd be going through. Having shoes needing arcing was/is more common than you would think, but primarily was used for oversized drums to contour the shoe to that different arc. I used to do it all the time.
If it is only happening at the last bit if tightening, not much chance it's shoes, unless they are conical shaped really badly.

 

[Jimflorida]

Thanks, will follow your suggestions. It does only bind on the final,tightening of the nuts on the drum, as you stated. Jim

 

[Jimflorida]

Thanks for your replies--it really helps to get different perspectives on a problem. It turns out that the inner edge of the drum needed to be trimmed a bit (about 1/8) because it was rubbing up against the brake backing plate. Hey, you learn something new every day. Jim

 

[Deleted member 8987]

That's why I led you down that path. Sometimes, one drum will be cast differently than the other....especially if one is a replacement. With axle to backing plate offset, might work fine on one side and not the other. Seen it before, and most recently on a RF drum setup on a 1941 Lincoln Continental Convertible.

 

[Jimflorida]

Yes, that was the case with mine. The right side was fine, and the left had the problem. Jim