Brake Drum Width?

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2fine69s

2fine69s

69 340-6pak Rag Top
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Hey guys,
I have just put the brakes on the 8.75 that i have installed in my 69 Dart. My question is should the brake drum slide completely over the backing plate? Mine has about a 1/4" of brake shoe showing when the drum is all the way against the axle. Do I have the wrong size drums?
Martin
 

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Yes, drum should reach the back of the backing plate. Measure your shoes & the drums. You probably have 2-1/2 " shoes on 2" drums. Does the drum rest against the axle flange when it's on all the way? The center hub of the axle flange should protrude through the drum so the wheel can center itself on the axle.
 
later big bolt pattern (5X4.5) 7 1/4" and 8 1/4" rears use wider drums and brake shoes than the earlier small bolt pattern (5X4) 7 1/4" and 8 3/4" rears,
if you try and fit the wider brake shoes into the narrower brake drums, this is what happens
 
Axles are Yukon 4.5 patten, green bearing. The drum fits all the way up to the axle flange. Drum ID measures 2.25". The shoes measure 1.75". I picked all this stuff up separately, with long intervals in between and I must have miss matched somewhere. I would like to put about what would come on a 69 GTS, What do I need to make my stuff match up?
 
2fine69s said:
Axles are Yukon 4.5 patten, green bearing. The drum fits all the way up to the axle flange. Drum ID measures 2.25". The shoes measure 1.75". I picked all this stuff up separately, with long intervals in between and I must have miss matched somewhere. I would like to put about what would come on a 69 GTS, What do I need to make my stuff match up?
Click to expand...

I'm in the middle of a mix 'n' match too. I'm gonna get stuck buying 11X2 1/2" drums for '68 b-body rear. More money than I wanted to dish out.

I still don't know what you did, but it looks like you will need larger drums. Are they 10" or 11". I'm guessing you can fit 2.5" shoes. If not, then I can only guess that the axels are too long, or the rear has been narrowed, or from a different body style and altered to fit.

Give us all the lengths and widths of what you do have, (part numbers if you have them) and the backing plate size, maybe this would be easy to figure where it went wrong.
 
Show a pic of the face of the drum.

Axles have to have the wheel bearing position machined for the brakes you are using - OEM A-body 1 3/4" backing plate/shoe/drum combo. Or the wheel bearing needs to be positioned for the 2" backing plate/shoe/drum combo.

Does that help in figuring out what got mismatched?
 
Ok, let me get this straight.

You have BBP Yukon axles.

You're trying to use SBP drum brakes. 1 3/4" shoes only came with SBP brakes. Did you have the SBP drums re-drilled for BBP?

Either way, you can't use SBP brakes on a BBP axle, or vice versa. The axle offset is different, SBP brakes only work with SBP axles. And not because of the bolt pattern, the axle stand off (offset) is different, so drilling the drums doesn't solve the problem.

If you have BBP axles, then you need to find a set of BBP brakes. Those would be 10x2.5, 11x2.5, 11x2, or even 11x3. All of the BBP brakes use the same offset (backing plates are different on the 2" and 3" brakes). 10x2.5" brakes are pretty easy to find at the junkyard.
 
OK guys, Now I think I've got it, I really appreciate your help, The shoes I purchased long ago are SBP, the backing plates are BBP, and the drum is anybodies guess so.....
I just ordered new 73 up BBP drums and shoes,
Thanks All,
Martin
 
2fine69s said:
OK guys, Now I think I've got it, I really appreciate your help, The shoes I purchased long ago are SBP, the backing plates are BBP, and the drum is anybodies guess so.....
I just ordered new 73 up BBP drums and shoes,
Thanks All,
Martin
Click to expand...

Do you know what the width of the friction surface on the new drums will be? Unless someone drilled those drums they must be BBP to fit on those axels. If you land up with new drums that are the same as the old ones you will still have a problem.
 
The Drums are 10"x2.5" BBP, the shoes are 2.5" also. I basically ordered parts for a 73 up Duster.
 
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