What size tires? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

*six-T-seven* · 05-03-2012, 05:34 PM

I have a set of wheels (18" x 8.5" w/4.5" backspacing) that I need some help with determining tire size.

The truck is a '72 stepside that's soon to be bagged and wanted to know your recommendations for tire size. I would like to have a little taller tire in the rear, but with only 4.5" backspacing I am afraid the tire will rub.

Any suggestions?

Pro Performance · 05-03-2012, 08:17 PM

If you have 8.5" on the rear with 4.5 of backspace, you will be Ok with a larger tire. How much is your truck lowered?

Just as a starting point, you can go with the sizes below, but may not work on a truck that is really low. These are sizes from the Nitto 420S line.

255/50/18: 28" Tall
255/55/18: 29" Tall

Give us a little more info and we can make a better recommendation.

*six-T-seven* · 05-05-2012, 12:27 AM

Thanks Pro Performance for the reply.

The truck will be on bags when the tires/wheels are installed. My concern is the lip on the underside of the fender rubbing the tire sidewall. The 71-72 had a wider (1 1/2" wider) rear end than the 67-70's from what I read here, that's where my concern comes in. I want to be able to "tuck" the tire/wheel in the rear fender without rubbing. I've seen the earlier models tuck the tire, but then again the rear end is narrower.

Pro Performance · 05-05-2012, 12:55 PM

No problem....

You will be Ok with that backspace. On a 10" wheel, a 5.5" backspace works great, but since you have an 8.5", the 4.5 will be fit no problem. Since it is narrower, you can have that shallower backspace. If anything, you have more clearance to the inner and outer fender than a 10" would @ 5.5 BS, and guys will run that on a bagged truck.

I don't see it being a problem at all.

*six-T-seven* · 05-05-2012, 06:06 PM

The rear end is wider by 1.500 inches, not narrower. The truck is a 72.

A friend of mine has 15 x 8 truck rally's with 255/60-15 tires on his bagged 71 and they rub at full dump. Does anyone know the back spacing on stock 15x8truck rallies?
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Pro Performance · 05-05-2012, 07:15 PM

Yeah, with the wider rear, they will be ok. I don't know about the backspace on the stock wheels, probably 4.5 if I had to guess. The wider rear plays to your advantage in this case.
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05-03-2012, 05:34 PM	#1
six-T-seven Account Suspended Join Date: Jan 2012 Location: Here and There. Posts: 100	What size tires? I have a set of wheels (18" x 8.5" w/4.5" backspacing) that I need some help with determining tire size. The truck is a '72 stepside that's soon to be bagged and wanted to know your recommendations for tire size. I would like to have a little taller tire in the rear, but with only 4.5" backspacing I am afraid the tire will rub. Any suggestions?

05-03-2012, 08:17 PM	#2
Pro Performance Registered User Join Date: Aug 2010 Location: AZ Posts: 3,069	Re: What size tires? If you have 8.5" on the rear with 4.5 of backspace, you will be Ok with a larger tire. How much is your truck lowered? Just as a starting point, you can go with the sizes below, but may not work on a truck that is really low. These are sizes from the Nitto 420S line. 255/50/18: 28" Tall 255/55/18: 29" Tall Give us a little more info and we can make a better recommendation.

05-05-2012, 12:27 AM	#3
six-T-seven Account Suspended Join Date: Jan 2012 Location: Here and There. Posts: 100	Re: What size tires? Thanks Pro Performance for the reply. The truck will be on bags when the tires/wheels are installed. My concern is the lip on the underside of the fender rubbing the tire sidewall. The 71-72 had a wider (1 1/2" wider) rear end than the 67-70's from what I read here, that's where my concern comes in. I want to be able to "tuck" the tire/wheel in the rear fender without rubbing. I've seen the earlier models tuck the tire, but then again the rear end is narrower.

05-05-2012, 12:55 PM	#4
Pro Performance Registered User Join Date: Aug 2010 Location: AZ Posts: 3,069	Re: What size tires? No problem.... You will be Ok with that backspace. On a 10" wheel, a 5.5" backspace works great, but since you have an 8.5", the 4.5 will be fit no problem. Since it is narrower, you can have that shallower backspace. If anything, you have more clearance to the inner and outer fender than a 10" would @ 5.5 BS, and guys will run that on a bagged truck. I don't see it being a problem at all.

05-05-2012, 06:06 PM	#5
six-T-seven Account Suspended Join Date: Jan 2012 Location: Here and There. Posts: 100	Re: What size tires? The rear end is wider by 1.500 inches, not narrower. The truck is a 72. A friend of mine has 15 x 8 truck rally's with 255/60-15 tires on his bagged 71 and they rub at full dump. Does anyone know the back spacing on stock 15x8truck rallies? Posted via Mobile Device

05-05-2012, 07:15 PM	#6
Pro Performance Registered User Join Date: Aug 2010 Location: AZ Posts: 3,069	Re: What size tires? Yeah, with the wider rear, they will be ok. I don't know about the backspace on the stock wheels, probably 4.5 if I had to guess. The wider rear plays to your advantage in this case. Posted via Mobile Device



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