Back spacing with disc and drum brakes

[Rusty one]

I'm starting to search for some wheels for my 63 C10 with front disc and rear drums. I'm looking to run 215/75/15 up front on a 6 " wheel and 235/70/15 rear with an 8" wheel. ( 6 lug wheel)
The truck will have full air ride with the ability to lay frame.

My question is ...what back spacing will I need upfront to clear the disc brake combination? I'm thinking 4" b/s in the rear,but not sure up front.

Any suggestions will be appreciated.
Thankyou

[The Rocknrod]

Anything told to you here would be a guess. Do you know how to take backspace measurements?

[Rusty one]

Originally Posted by The Rocknrod

Anything told to you here would be a guess. Do you know how to take backspace measurements?

Not without a wheel

[theastronaut]

I had 215/75 tires on stock 5.5" wide wheels up front with 1.5" bolt on spacers and CPP disc brakes on my lowered '66. You can see in the second pic how the spacers pushed the wheels out towards the fender edge to fill up the opening better. I added them for looks and to clear the calipers with stock drum brake wheels.

Stock 5.5" wheels have 3.75" backspacing so my spaced wheels were effectively 2.25" backspace.

Rear was 235/75 on an 8" wheel with 3 3/8" backspace. This should help get you in the ballpark.

[Rusty one]

Originally Posted by theastronaut

I had 215/75 tires on stock 5.5" wide wheels up front with 1.5" bolt on spacers and CPP disc brakes on my lowered '66. You can see in the second pic how the spacers pushed the wheels out towards the fender edge to fill up the opening better. I added them for looks and to clear the calipers with stock drum brake wheels.

Stock 5.5" wheels have 3.75" backspacing so my spaced wheels were effectively 2.25" backspace.

Rear was 235/75 on an 8" wheel with 3 3/8" backspace. This should help get you in the ballpark.

Thanks for the ballpark info...esp the pics.
Are the rear wheels a deep dish vs the fronts?

So a 2-1/2" b/s will clear a disc brake caliper?


Possibly other members who run similar sized tires& who have front disc and rear drums will let us know their combos.

Thankyou

[theastronaut]

Yes, the rear wheels are a good bit deeper than the front wheels. The backspacing isn’t what makes the wheel clear the caliper, it’s the shape of the inner barrel. Stock drum brake wheels are a 45* tapered design and need to be spaced out around 1/2” to clear, but disc brake wheels have a 90* step design that clears without spacers. So you could have any backspacing as long as the inner barrel has a 90* step. I can post pics of the difference tomorrow.

[Rusty one]

Originally Posted by theastronaut

Yes, the rear wheels are a good bit deeper than the front wheels. The backspacing isn’t what makes the wheel clear the caliper, it’s the shape of the inner barrel. Stock drum brake wheels are a 45* tapered design and need to be spaced out around 1/2” to clear, but disc brake wheels have a 90* step design that clears without spacers. So you could have any backspacing as long as the inner barrel has a 90* step. I can post pics of the difference tomorrow.

I was not aware of this. Thankyou for the lesson. Would like to see what the inner barrel looks like when you can

[PGSigns]

I have wheel vintuqes 12 series wheel on my 66 and wit a 225 75 15 on the front with a 6" wheel with 3" of back spacing have no issues with the disc brakes or the lower control arms. On the rear I am running a 255 70 15 on a 8" wheel with 4" of back spacing and wit the tire I have they will rub the inner side of the wheel house going in some parking lots. I like a 7" wheel for a 235 tire. I think it keeps the sidewalls in a better shape.
Jimmy

[Rusty one]

Originally Posted by PGSigns

I have wheel vintuqes 12 series wheel on my 66 and wit a 225 75 15 on the front with a 6" wheel with 3" of back spacing have no issues with the disc brakes or the lower control arms. On the rear I am running a 255 70 15 on a 8" wheel with 4" of back spacing and wit the tire I have they will rub the inner side of the wheel house going in some parking lots. I like a 7" wheel for a 235 tire. I think it keeps the sidewalls in a better shape.
Jimmy

Thanks Jimmy...good to know

[theastronaut]

The blue wheel is a drum brake wheel with a 45* slanted inner barrel. The other has a 90* stepped inner barrel that makes room for a caliper. Both are factory 5.5" wide six lug GM wheels with three nub centers (three nubs that hold the hubcap on), so the rule of thumb that all three nub wheels won't clear disc brakes isn't quite true. The three nub wheels that will clear discs are a lot more uncommon though. There are later model GM six lug wheels with four hubcab nubs that will clear discs as well, those are easier to find.

[Rusty one]

Originally Posted by theastronaut

The blue wheel is a drum brake wheel with a 45* slanted inner barrel. The other has a 90* stepped inner barrel that makes room for a caliper. Both are factory 5.5" wide six lug GM wheels with three nub centers (three nubs that hold the hubcap on), so the rule of thumb that all three nub wheels won't clear disc brakes isn't quite true. The three nub wheels that will clear discs are a lot more uncommon though. There are later model GM six lug wheels with four hubcab nubs that will clear discs as well, those are easier to find.

I always say ,pictures help...and this one definitely does! Thanks
If I'm looking for stock type wheels,I'll know what to look for besides the bolt pattern.
If I were to order aftermarket wheels I will need to know the backspacing,boltpattern,width and tell them the wheels are for a later model Chevy C10 (78-87)? Would that statement be correct?

I'm learning guys, just be alittle patient..