Wheel Backspacing

[LT-102]

On a 71 C20 with no suspension modifications what is the maximum backspacing I can use for wheels without causing a problem at the front or rear? Currently I have 4-3/4". Thanks in advance for the help.

[LT-102]

ttt

[LT-102]

ttt Just one more trip. I really need to know.

[Scrub]

I'm a little confused. You want the tires to be wide, correct? and you want to know how far of an offset you can have in the wheel center to make the tires stick out?

or do you want to know how far in the wheel can be from the drums and not hit something when you turn?




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Scrub
70 GMC 1,000,000 + miles
72 K-20 project, 456 Dana60 front, Corp14 rear w/locker, 265R19.5 tires 20-ply. Warn 12k winches both ends, Cross-over steering with raised tie-rod, Powerbox steering, 4500 watt 120-AC power, Air, Hydraulic aux power, 4 inch lift, 5000 lb air-bags both ends.

[Mike C]

This isn't really a question for the internet, but for a tape measure and straightedge. Many factors determine what will and won't fit, including how your individual truck is put together. You never said what diameter wheel or what width or what tire you want. Things like tie rods might interfere with a 15" rim but not a 17".Take a tire off, get a straightedge or make you a fitment gauge from a piece of all-thread and 1" angle iron. The angle should bolt to the rotor or drum face and the all thread should be the section width of the tire you expect to run. The all thread should run through the angle iron at a distance equal to the radius of the tire from the centerline of the spindle. Now you can adjust backspacing with the all thread and turn the tire left to right checking ACTUAL clearance on your truck. Wheels and tires can be ordered from this.

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70 GMC 3/4 ton Sierra Grande 402/TH400
72 Jimmy 4WD 4spd 4" & 35's
64 Corvette Coupe
68 Camaro 'vert TPI & TH700
69 Z/28 355 12.6's @110
72 Datsun 240Z-ol' reliable

[71GMCstreet]

4 3/4" is as about as close as you are going to get. With that said, a 15x10 rim with that backspacing will hold.....comfortably...a 275 - 60 - R- 15 tire. If you want more backspacing, and a wider profile, there is a very, very cheap and real quick way to do that, I'm gonna do just that this year on mine, while the bed if off the truck.

[Tim Christian]

As Mike C said it is hard to answer this question but I have asked it myself on my daily driver(fleetside) which has a 72 frame under it(this rearend is longer than my 67) I have 15x10's with 4-1/4 back spacing running 275/60/15 tires and on my ground up a orginal 67 stepside I am running 15x10's with 275/60/15's with 4-1/2in backing spacing. So like 71GMCstreet said about 4-3/4in is about all you are going to get without mods.

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67 GMC Stepside(UNDER CONSTRUCTION)
67 GMC Custom
67 Chevy C-30