Need help with rim size

[jjmaple]

I have a '70 C20 that I would like to replace the stock rims with aftermarket ones that will provide me with the necessary clearance to install first disc brakes. My questions are as follows:

1. What is the widest rim size on a 16" wheel that I can go without clearance issues? The truck is not and will not be lowered.

2. Do I need a specific offset or is "0" offset the way to go?

3. I have seen mention that any '65 to '09 Chevy/GMC factory 8 lug rim will fit my truck. Is this true?

Thanks in advance for your help.

[laid_out_70]

i have the same questions about the exact same truck. except i want mine laid out and on 20"

[BlackTopMotors]

That's a good question! I have a 71 riding stock height with 0 offset.

[Kiwi]

For what it's worth, I recently upgraded my 1971 2WD long bed with a set of 18x8-inch repro rally wheels and all fits fine with the factory disc brakes on the front of the C10.

[BlackTopMotors]

Originally Posted by Kiwi

For what it's worth, I recently upgraded my 1971 2WD long bed with a set of 18x8-inch repro rally wheels and all fits fine with the factory disc brakes on the front of the C10.

If you get a chance to take a pic that would be great! Do you think you could get away with 18x10's rear wheels?

[Kiwi]

BlackTopMotors,

With the truck lowered 2-inches all the way around, the 16x8's with 235/70R16 tires fit within the factory wheelwells with absolutely no problem. A 16x9 would easily clear, but a 16x10 would be getting pretty tight as the rim would start hanging outside of the wheelwell. However, you would have to do some measurements to see what backspacing would work best. While I'm not positive, I seem to recall that my 16x8s have a 5-inch backspacing.

I just crawled under my truck with a flashlight and did some quick measurements and photos and here's what I have to offer.

1. While there is a ton of room between the inside lip of the wheel and the leaf spring (at least 4 inches), the top of the tire is already pretty close to the inside lower edge of the wheel tub. The wheel/tire could go inboard another 1/2- to 3/4-inch, but anything more would could cause rubbing during body roll and/or when loaded.

2. There is tons of room for the wheel to go out, but at some point it will start looking a bit ghetto. Thus, I might call it safe and go for a 9 or 9.5-inch wheel rather than a 10.

Photos:

- Photo 1 shows the wheel edge to spring clearance (lots)
- Photo 2 shows the tire edge to inner wheel tub clearance (not much)
- Photo 3 shows the alignment of the outside of the tire to the outside of the sheetmetal (somewhat flush with lower edge of fender, yet top of fender lip hangs over tire by a few inches)

[Kiwi]

I just realized that I made a goof in an earlier e-mail. I upgraded to 16x8-inch rally wheels ... not 18x8-inch.

However, with that said ... if I were doing an aftermarket wheel (I considered a set of American Racing Salt Flat wheels), I would probably do a 17x8.5 all the way around. With an 18-inch (or larger) diameter wheel, the sidewall starts to get pretty shrimpy which is fine for a car ... but looks a bit odd on a full-size truck.

Just my two cent's worth.