Why 10" or 11" rear drums?

[Daytona Jim]

I've been told b body big block cars (66-70) with disc brakes came with 10" drums. Drum brake cars came with 11" drums in the rear. Is this true? Thanks

 

[451Mopar]

The R/T Drum brake cars had 11" drums front and rear. Not sure if that is a "package" or option thing? Not really a big deal because most of the braking is done with the front brakes.

 

[Jerry Hall]

My 2 67 Hemi 4-speed GTX'S have Kelsey Hayes front disc brakes and 10" drums on the Dana. Special Order may be different. I don't know what brakes would be included with track pack packages. There may be many variables on this. As stated either will do the job as the front does most of the braking.

 

[moparnation74]

The R/T Drum brake cars had 11" drums front and rear. Not sure if that is a "package" or option thing? Not really a big deal because most of the braking is done with the front brakes.

Called the HD suspension package

 

[R413]

Answer to the first question is YES. Disc brake front B&E bodies 1966-1971 came with 10” rear drums.

Doesn’t matter if BB or SB or slant six or hemi. The super track pack 4.10 cars came with the same brakes also.

Except the 1970 T/A and AAR. All had front disc as std equipment and the rear drums were 11” on these.

 

[Kern Dog]

They probably figured that with the discs, the rear sizing could be downgraded to the 10" drums since the overall braking force was still much greater??