Rear Drum Brake Stupid Question

[JimAndA72]

I have a '72 that already has the power front disc brake conversion from Tom's that was done a couple years ago. Everything still seems right in the front but I have pulsing during braking at slow speeds so I'm thinking I need to do a rear brake job. I've done many brake jobs on vehicles in the past so I'm comfortable doing this. My question is about the size of my drums. All of the online places and also the local parts stores list a 10" and 11" drum for the 72's. Forged into my rear drum it says "10.09 inch max diameter." It doesn't sound logical that 9/100th's of an inch would be the maximum allowable wear on a 10" drum. Was there also a 9" drum brake on these?

This is my DD and my only vehicle at the moment and money is tight so I want to have all of the replacement parts on hand, (shoes, wheel cylinders, drums, spring kit) before even jacking the truck up again. I work 6 days a week so I have to get this done without a bunch of trips to the parts store. Wishing I could afford the rear disc brake conversion bu I can't right now.

Thanks for any input.

Jim

 

[garberz]

There were only three different size rear brakes available for the Bronco. 10"x2 1/2" 66'-75'. 11"x1 3/4" 66'-75'. 11"x2 1/4" 76'-77'. Sounds like you have the 10'x 2 1/2" rears.
I'm not a fan of rear disc, the drums work great, for as little braking they do and the parking brake works so much better than the caddy calipers. A lot of expense for no real gain other than adding bling. Just my opinion.

Mark

 

[BUCKNBRONK]

pulsing? i would check the "run out" of the front disc's, I bet u have warped or dished rotors. I think u r cornfusing 9 hundreds with 9 thousands of a inch, its a big difference.. as far as i have seen, no, no 9" drums, even if u had 9" drums u would not be able to remove 1 inch of material from them for resurfacing.

 

[PuenteMart]

you might have the ABS option on your bronco! ;D

 

[Apogee]

That sounds about right...IIRC, the 11" drum has a wear limit of 11.090", so it would make sense to me that the nominal 10" drum would be comparable.

Brake pulsing (judder) is such a general brake symptom, I wouldn't assume it's the rear drums, as it could just as easily be disc thickness variation (DTV) with the front rotors, commonly referred to as "warped rotors". There are numerous potential caused for DTV, including improper installation with excessive rotor runnout, improper bedding-in, improper pad compound for the type of vehicle/driving, overheating of the rotors/pads, pad etching, manufacturing defects, etc.

Do you feel any side to side component to the pulsing? How about anything through the steering wheel? If so, it's probably the front, not the rear.

All that said, it could be the rear, I just wouldn't assume that without more information.

HTH,
Tobin

 

[JimAndA72]

That sounds about right...IIRC, the 11" drum has a wear limit of 11.090", so it would make sense to me that the nominal 10" drum would be comparable.

Brake pulsing (judder) is such a general brake symptom, I wouldn't assume it's the rear drums, as it could just as easily be disc thickness variation (DTV) with the front rotors, commonly referred to as "warped rotors". There are numerous potential caused for DTV, including improper installation with excessive rotor runnout, improper bedding-in, improper pad compound for the type of vehicle/driving, overheating of the rotors/pads, pad etching, manufacturing defects, etc.

Do you feel any side to side component to the pulsing? How about anything through the steering wheel? If so, it's probably the front, not the rear.

All that said, it could be the rear, I just wouldn't assume that without more information.

HTH,
Tobin

I feel absolutely nothing in the steering. I was thinking I'd try the rear drums first because they haven't been reworked in the 3 years I've owned the truck. Hoping I don't have any of those issues going on in the front. I had a shop do my front disc conversion a couple years ago

 

[Timmy390]

I have pulsing during braking at slow speeds so I'm thinking I need to do a rear brake job.

I would think just the opposite. I bet it's the front rotors. I have the same issue on brand X car and I know it's the rotors.......

I would back the rear brakes off all the way and then see if the pulsing goes way. If you're fronts work as well as mine, you don't need the rears anyway.

Could be warpped drums but I bet not.

Tim