Tall 15" tires?

[jagarra]

I am looking for some tall 15" tires to fit my 62 GMC, most I have found are in the 29-30" range. Does anyone know of a manufacturer that has something a bit bigger in diameter? I have a 3;54 rear end ratio, SM420 tranny.

thanks

[James]

You might have to go with a larger rim. I went with 16" rims and my tire diameter is 31.7". I too have a 3.54:1 rear axle and a SM420 transmission.

[jagarra]

James,

You may be right, from all the looking I have done the best is 30.5" diameter and that was in a snow tire. Problem is that I have original 3 piece rims with hub caps that I don't want to give up. Probability is that I won't take it much on highway anyway so it would be hard to justify buying all new rims and tires for an extra 5-7mph on the road.

thanks,

gg

[James]

According to my numbers with a 30.5" tire you will have:
2150 rpm = 55 mph
2350 rpm = 60 mph
2550 rpm = 65 mph
2750 rpm = 70 mph

With a 29" tire:
2250 rpm = 55 mph
2450 rpm = 60 mph
2650 rpm = 65 mph
2850 rpm = 70 mph

On my truck with 16" rims and a 31.7" tire:
2050 rpm = 55 mph
2250 rpm = 60 mph
2450 rpm = 65 mph
2650 rpm = 70 mph

All of these numbers should be within ±2 mph.
There is not a lot of different between the tire sizes. So whatever you decide to use, it is not going to make a big difference.

[63gmc4x4]

Im running 31x10.5 on min 8 wide wheel lowered 4 inches no rubbing

[BillT]

Not sure of the height, but I needed a taller tire for the Rears on my '72 C-10. I am using 265/75/15's. Not a whole lot, but it did make a difference.

[James]

Originally Posted by 63gmc4x4

Im running 31x10.5 on min 8 wide wheel lowered 4 inches no rubbing

According to the info I found online for this tire size it is approx. 30.67" dia.

Hope this is helpful.

[jagarra]

I decided to go with an option that let me keep the 3 piece rims. When I purchased the truck two tires were shot so I replaced them with new keeping the best of the ones left on there, I matched a set of Lee tires for the front. I believe these tires are pretty old and I have been getting the square tire ride for the first hour or so of operation. So I ordered some mud/snow tires from STA (30") that will go on the rear and the ones purchased a couple years ago will go on the front. This should give me some rubber that should last for awhile. I do have a set of chrome spoked wheels that are 15x8" diameter that came with truck if I decide to go to tubeless radials.