Rear drums rubbing
You can see in this picture the difference in the axle flange offset between the BBP and SBP axles. With factory axles it's easy to tell, all you need to know is the bolt pattern to identify the flange offset. If you re-drill factory SBP axles for the 5x4.5" pattern, you have to use your SBP 10x1.75" brakes and re-drill the drums. Simple. Moser messes that up a little, as I mentioned earlier, they make axles that have the SBP flange offset with the large bolt pattern. Because they're not re-drilled, they look like BBP axles. But the axle flange measurement is for a SBP axle. Those axles also MUST use SBP 10x1.75" brakes with re-drilled drums.
The axle flange offset means that the backing plates have a different offset from the end of the housing. You can measure this to determine which backing plates you have, if you aren't sure. It's a little hard to tell, but in this picture the bottom 1/3 of the backing plate is hanging off the bench. That's so the outer lip of the backing plate is flat on the bench. To do that you have to hang the bottom part of the backing plate that has the emergency brake "bumps" off the bench so the backing plate sits flat.
With the e-brake bumps off the bench and the outer lip of the backing plate flat, measure from the axle flange mount down to the bench. If you have a 10x2.5" backing plate, that measurement should be about 1.75". If you have a 10x1.75" backing plate, that measurement is more like 1.25". Not all tape measures are equal and not all backing plates and benches are flat, but that's a half inch difference so you should come up with something that's about an 1/8" from one of those measurements, which will tell you if you have the 10x1.75" SBP backing plate or the 10x2.5" BBP backing plate.
You can see in this picture the difference in the axle flange offset between the BBP and SBP axles. With factory axles it's easy to tell, all you need to know is the bolt pattern to identify the flange offset. If you re-drill factory SBP axles for the 5x4.5" pattern, you have to use your SBP 10x1.75" brakes and re-drill the drums. Simple. Moser messes that up a little, as I mentioned earlier, they make axles that have the SBP flange offset with the large bolt pattern. Because they're not re-drilled, they look like BBP axles. But the axle flange measurement is for a SBP axle. Those axles also MUST use SBP 10x1.75" brakes with re-drilled drums.
The axle flange offset means that the backing plates have a different offset from the end of the housing. You can measure this to determine which backing plates you have, if you aren't sure. It's a little hard to tell, but in this picture the bottom 1/3 of the backing plate is hanging off the bench. That's so the outer lip of the backing plate is flat on the bench. To do that you have to hang the bottom part of the backing plate that has the emergency brake "bumps" off the bench so the backing plate sits flat.
With the e-brake bumps off the bench and the outer lip of the backing plate flat, measure from the axle flange mount down to the bench. If you have a 10x2.5" backing plate, that measurement should be about 1.75". If you have a 10x1.75" backing plate, that measurement is more like 1.25". Not all tape measures are equal and not all backing plates and benches are flat, but that's a half inch difference so you should come up with something that's about an 1/8" from one of those measurements, which will tell you if you have the 10x1.75" SBP backing plate or the 10x2.5" BBP backing plate.
