Rear drum brake question.

[R413]

Hello I new here, but have owned RR and GTX cars for 35 years.

Now the RR and GTX manual drum brakes were 11x3" front and 11x2.5" rear. This is 1967-1970.
I have never seen a 3" rear drum a on a B-body from these years.

The backing plates are specific to the shoe width. That big pin at the top anchors the shoe. It is a different length for different width shoes. The spine of the shoe is always in the middle the shoe from side to side. So you cannot put a 2.5" wide shoe on a 2" backing plate, the spine won't hit the anchor, then it will be too far out.

Does this make sense?

 

[65wgn440]

Must contradict above post. Had a '67 GTX with factory 4 wheel drums, 11" x 3" all the way around. In fact, I wrecked that car and now have those same brakes on my current '67 Belvedere.

 

[miller]

Drum backing plates, front to rear, would have totally different hole patterns, right??? Front spindle vs rear axle flange.

Drums themselves probably interchange, wheel stud patterns the same.

 

[70 RR]

That difference in diameter is so small, why didn't they just make them the same???

 

[Fran Blacker]

Drum backing plates, front to rear, would have totally different hole patterns, right??? Front spindle vs rear axle flange.

Drums themselves probably interchange, wheel stud patterns the same.

Center hole smaller on fronts, its not much .020 appox..

 

[Dipstick]

11x3 brakes in the rear would lock up way to early in my opinion.

Not if the wheel cylinder diameter is proportional to the shoe width.