LBP vs SBP 8.75 Brake Backing Plates

[65 Dartman]

Had a friend bring over 3 sets of 8.75 brake backing plates. He said he thought 2 sets were from an A Body 8.75 and 1 from a B Body but could be the other way around as he didn't mark what came from what when he removed them long ago. What's the easier way to tell/show him which ones fit what?

 

[72bluNblu]

Lay the backing plates flat on a table and measure from the table up to where the plate bolts to the axle flange. You'll need to hang the bump for the E-brake cable off the edge of the table to get them to lay flat.

Assuming they're all backing plates for 10" drums, if that measurement is 1.75" it's a 10x2.5" BBP drum backing plate. If it's not then it's a 10" SBP backing plate. I had that measurement somewhere too but I can't find it at the moment. At any rate if they're 10" rear drum backing plates there's only two options anyway.

 

[B-onefan]

If you put a BBP axle in a a body 8 3/4, which backing plate do you use?

 

[65 Dartman]

If you put a BBP axle in a a body 8 3/4, which backing plate do you use?

I do know in that scenario you have to use a BBP backing plate because of the thicker BBP axle flange

 

[replicaracer43]

You have to be careful, because there ARE BBP axles made with the offset to use the SBP backing plates...

 

[72bluNblu]

I do know in that scenario you have to use a BBP backing plate because of the thicker BBP axle flange

Sort of. The flange isn't significantly thicker, but the flange offset is different. So, if you have OE BBP axles or aftermarket axles with the BBP flange offset you need to use BBP brakes.

You have to be careful, because there ARE BBP axles made with the offset to use the SBP backing plates...

Yes exactly.

All OE BBP axles have the same flange offset. So, in that scenario you always use BBP brakes.

But, you can get aftermarket BBP axles with the SBP flange offset. If you do that, or if you redrill your SBP axles for the 5x4.5" bolt pattern, you have to use SBP brakes with re-drilled drums.

 

[65 Dartman]

Lay the backing plates flat on a table and measure from the table up to where the plate bolts to the axle flange. You'll need to hang the bump for the E-brake cable off the edge of the table to get them to lay flat.

Assuming they're all backing plates for 10" drums, if that measurement is 1.75" it's a 10x2.5" BBP drum backing plate. If it's not then it's a 10" SBP backing plate. I had that measurement somewhere too but I can't find it at the moment. At any rate if they're 10" rear drum backing plates there's only two options anyway.

View attachment 1714979469

I checked them per your instructions and one set is for an A Body SBP, the other 2 are LBP backing plates. Thanks again for your help!