What Size Brakes Do I Have?

[1967coronet]

Just a thought... call the shop doing your restoration and ask them to measure a rear drum.

 

[RR Fan Dan]

Just a thought... call the shop doing your restoration and ask them to measure a rear drum.

I did that. Hopefully today.

 

[RR Fan Dan]

They are 11”. @mobileparts PM sent.

 

[ynst]

drum/drum 11" rears
disc/drum 10.5" rears

 

[cudamark]

What do you have for front brakes? Disc or drum?

By 1974 all Mopars came with disc brakes up front, except for the W100 and some A-bodies.

 

[mobileparts]

^^^ ynst ^^^
There is NO SUCH THING as 10 1/2 “
———————————————————-

 

[33 IMP]

^^^ ynst ^^^
There is NO SUCH THING as 10 1/2 “
———————————————————-

......drums.

 

[mobileparts]

^^^ N O ^^^
10 “ ( NOT 10 1/2 “ EVER ) Brake Shoes utilize
10 “ Brake Drums —- A L L —- O N L Y —-

 

[Don Frelier]

^^^ ynst ^^^
There is NO SUCH THING as 10 1/2 “
———————————————————-

Unless the are really completely worn out drums

 

[ynst]

Unless the are really completely worn out drums

I measured the drums on the junk '69 Road Runner rear in my shed and they were just that, worn out and closer to 10-1/2 than 10 but they definitely weren't 10" and were well under 11"

I just went out in the garage and dug out and checked the box of brand new spare shoes for my GTX and they are, indeed,10 inch.

Sorry for the confusion.

 

[PsyOps]

IIRC, if changing from front drums to discs, won't you need a new/different proportioning valve? I ask because I didn't see it listed.

 

[ynst]

Drum and disc brake systems operate on different pressures so, yes, you will need the proper proportioning valve as well as a disc/drum master cylinder as the bore sizes are different as well and the disc brake port does not have a residual valve in it.

If you use a drum/drum master cylinder with disc brakes, the residual valve will prevent the brake fluid from returning to the master cylinder when you take your foot off the pedal and the pads will still be dragging on the rotors.