Smaller/thinner rear brake drum? Deep rear steelies won't fit!

[vintage_mpg]

So we're working on a cool ol '82 sab, and the truck came with a brand new set of custom deep 15" steel wheels that we're really anxious to get installed...but they're just barely not fitting!

Our existing rear drum brakes have a drum with a tall exterior lip that is just BARELY keeping the rear wheels away from seating as they should be.

Does anyone know if we can get a slimmer rear drum?

Or do we have to convert to disk brakes to get these bad boys installed?

Hopefully you can see what we're up against in these images:

[geezer#99]

Easiest way is with wheel spacers.


https://www.speedwaymotors.com/Unive...nch,28323.html

[vintage_mpg]

Originally Posted by geezer#99

Easiest way is with wheel spacers.


https://www.speedwaymotors.com/Unive...nch,28323.html

Then my wheel studs won't be long enough...

Do I need to swap them out as well, you think?

[vintage_mpg]

I'm afraid that the remaining half inch might really make a right difference in that rear wheel well.

The wheels are 10" wide, so it's going to fill that rear wheel well completely, I think. Width-wise that is.

[geezer#99]

Ooops!
True enough!
Adaptors then.



https://www.summitracing.com/parts/c...SABEgIM8_D_BwE

[vintage_mpg]

Originally Posted by geezer#99

Ooops!
True enough!
Adaptors then.



https://www.summitracing.com/parts/c...SABEgIM8_D_BwE

The adapters would work, in theory. That may be what we end up doing.

However, I think we'd be bumping up against the outer fender lip - or darn close to it.

Wondering about the brake drum option. Anyone know if I can get a flat-topped brake drum?

[Dead Parrot]

Define BARELY. Is it the whole height of the raised rim or just a 1/8 of an inch or so? If in is really BARELY, maybe you could have the fraction of an inch machined off. Taking off too much might weaken the drum too much.

For some years, there were different sizes of brake systems depending on GVW rating. If you have the larger one maybe you could sub the smaller set in its place.

[Warrens69GMC]

Auto parts stores have .250 wheel spacer in stock so you could try them, FWIW

[Nick_R_23]

Bring your drum down to the parts store and compare to a new one. That doesn’t look like an OE drum.

[vintage_mpg]

Originally Posted by Nick_R_23

Bring your drum down to the parts store and compare to a new one. That doesn’t look like an OE drum.

The truck was originally equipped with the 6.2 diesel...so it may have very well had larger rear brakes - but I can't find anything to validate that online. Looks like all of the half ton trucks all shared the same rear brake setup. At least according to what I've discovered in service manuals at this point. But it's been a long time since 1982!

I'll see if my local parts guys can find something different. The spacers are a great thought, but I think I'll need that additional quarter inch if I can figure out how to get these wheels to fit over that drum.

[Pontiac1976]

Ok looking at your wheel is the lip of the drum folded part of the rim that is not weld. If so just grind the fold lip of the inner rim none welded off. Because it looks like it taking up about 3/16 to 1/4" of space of room compared to the weld lip.
The rim's may not be made for C10-1/2Ton direct bolt on.
Try to lay the drum line up with the lug holes flat if it hitting those lips then the the fix.
Or take it to a shop get it done.

[ACS]

There were at least two different size brake options, but it was the width of the shoe that changed, not the drum diameter. I don’t think that helps your situation.

[Corts60]

Originally Posted by Cptmoney

The truck was originally equipped with the 6.2 diesel...so it may have very well had larger rear brakes - but I can't find anything to validate that online. Looks like all of the half ton trucks all shared the same rear brake setup. At least according to what I've discovered in service manuals at this point. But it's been a long time since 1982!

I'll see if my local parts guys can find something different. The spacers are a great thought, but I think I'll need that additional quarter inch if I can figure out how to get these wheels to fit over that drum.

You most likely have the HD brake package which is wider shoes and drums. They were ordered with various combinations.

[v30crewcab]

the diesel had the hd brakes. you will need backing plate out to convert to the thinner brake shoe setup. I'm sure someone will trade you.

[vintage_mpg]

Originally Posted by v30crewcab

the diesel had the hd brakes. you will need backing plate out to convert to the thinner brake shoe setup. I'm sure someone will trade you.

Should I just make the transition to rear disks?

I see the kits for $350ish just after a very quick and dirty search. I'm guessing that to swap from the backing plate out would be close to half of that, if not more. Might be a good time to make the leap? Any thoughts?

Anybody tackled this swap recently?

[Warrens69GMC]

I would buy 1 replacement drum and try it and see if that works first.

[vintage_mpg]

Originally Posted by Warrens69GMC

I would buy 1 replacement drum and try it and see if that works first.

Ahh - I gotcha.

For that matter, I could toss one of the rear wheels into the truck and run it down to the parts store. A quick test-fit of the different style rear drums would let me know right if they would work or not.

Good ideas!

[vintage_mpg]

Originally Posted by Corts60

You most likely have the HD brake package which is wider shoes and drums. They were ordered with various combinations.

I think you're on to something here.....

From a quick check on Rock Auto, I see two different rear brake widths....one is 2" wide, and the other is 2 3/4" wide. I bet that's what I'm up against!

So can I just swap the shoes and the drum, you think? Or will I need to swap everything from the backing plate out? That's an interesting question....one that I'm afraid I'll just have to dive right into before figuring it out. I'm guessing that's the hiccup I'm up against at this point. I'll know more, soon enough!

[Hammered 77]

The backing plates are different also. I was going to up grade from the 2" to the 2 3/4 and I would have had to swap backing plates.

[vintage_mpg]

Originally Posted by Hammered 77

The backing plates are different also. I was going to up grade from the 2" to the 2 3/4 and I would have had to swap backing plates.

Dagger. I was afraid of that.

So at this point I'm guessing a rear disk swap is the way to go.

I am going to play with some wheel spacers to see what comes of that just in case, but I'm betting things are going to be too tight for that to be the answer.

All of this points to why the PO never got around to installing these brand new wheels! Lots of hassle involved.

What's the rear disk swap like? Difficult? Can it be done in a weekend? I'm nervous about it, having never tackled a brake swap like that.

[vintage_mpg]

Can a guy even order just the backing plates?

EDIT: looks like the backing plates are readily available, if I can just figure out which one is the correct one to make things work.

I'm going to price out both ways and see what comes up. Prob much simpler to keep the rear drums if possible. May not necessarily be any cheaper, but likely a much easier job.

[geezer#99]

What about swapping out the complete rearend?

[Dead Parrot]

One thing to watch for is not all disk brake conversion kits include a parking/emergency brake feature.

[vintage_mpg]

Originally Posted by geezer#99

What about swapping out the complete rearend?

This thought crossed my mind....but I didn't want to get that involved. At least not yet!

The truck has a Spartan locker in the rear, so it's set up nicely right now. I'm just trying to squeeze in these large wheels and tires. But it's turning out to be quite the chore!

The disc brake swap looks pretty involved as well, at least at first glance. Not sure I can do this without some coaching.

The drum swap (to the smaller width shoe size) is probably the way I'll have to go. Again - that's without playing with the spacers or anything as of yet....

[geezer#99]

Depending on the design of the backing plate you might need to pull the axles to change them out.

Maybe wheels that fit are the best option.