***7.25 brakes on 8.75 rear-end?*** "SOLVED"

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What bolt pattern?

BBP brakes are swappable from 7 1/4's to 8 1/4's, 8 3/4's, or even Dana's, but all the axles need to be BBP.

Not sure if the SBP 7 1/4 brakes will swap to a SBP 8 3/4 though.
 
Don't believe it works, but haven't tried yet!! Maybe ill throw one at each other and see if it works and report back!! Geof
 
I did it, went from 7 1/4 BBP to a 8 3/4 that was SBP but I got moser axles for BBP. I ended up not having to modify anything but, others have had to deal with the other stud or hole, which really isn't a big deal. I would think it should swap rite over.
 
SirDan said:
I did it, went from 7 1/4 BBP to a 8 3/4 that was SBP but I got moser axles for BBP. I ended up not having to modify anything but, others have had to deal with the other stud or hole, which really isn't a big deal. I would think it should swap rite over.
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He's doing SBP to SBP, not BBP to BBP. By putting BBP axles in your 8 3/4 you took care of the offset issue with the SBP 8 3/4 axles. The BBP brakes will swap onto any BBP axle, from the 7 1/4 all the way up to the Dana.

From what I understand, SBP 8 3/4" brakes are an entity unto themselves because of the unique offset used on the SBP 8 3/4 axles. I don't believe the backing plates will swap from a SBP 7 1/4 to a SBP 8 3/4. The guts will, but I don't think the backing plates will. But I haven't tried it either, I don't have any SBP 7 1/4's.
 
cosgig said:
Don't believe it works, but haven't tried yet!! Maybe ill throw one at each other and see if it works and report back!! Geof
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Cool Geof...I'd appreciate if you could do that!! Sure would save me a bunch of time and dough, if it works!

Thanks all for the replys!!
 
Unfortunately, small bolt pattern 7.25" backing plates will not bolt to an 8.75" rearend.
 
DoctorDiff said:
Unfortunately, small bolt pattern 7.25" backing plates will not bolt to an 8.75" rearend.
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i second this

just tried a few months ago to put my 69 9" 7 1/4 drums on a 70 8 3/4. the patterns look the same, sub the extra bolt, but the 7 1/4 bolt to bolt is just the right size to make drilling the backing plates dangerous.
 
buckshotbishop said:
well i have no experience with the 10 inchers so i cant say. though i would think they still wont work. if your drums are 10 x 1 3/4 i have backing plates if you need them
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Thanks for the offer of the backing plates. I actually already have 8.75 backing plates and such...I just redid my 7.25 rear brakes recently and was hoping ,if they would swap complete to the 8.75 ,it would save me some $$$ and time.
 
DoctorDiff said:
Unfortunately, small bolt pattern 7.25" backing plates will not bolt to an 8.75" rearend.
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Cass has spoken! If he says its a no-go, then it's a no-go

65Val said:
My 7.25" is 10" drums (V8 car), if that matters any.
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The problem isn't the size of the brakes, its the offset on the axles. The backing plates for the 9" and 10" drums have the same offset for the SBP 8 3/4 axles, so if one won't work, neither will the other.
 
Ok, I'm convinced. I just compared my 8 3/4 axles with the 7 1/4 currently in the car, and , they aren't the same measurements, so, even without the pesky 5th bolt situation, the backing plates still won't swap. Like DrDiff says...

The small bolt 10" drums will interchange, but the backing plates will not.
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To begin with, the dimension of the 2 bolts in the yellow circle are way off....
 

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