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Suburban Tire Question

post #1 of 9
Thread Starter 
I have a 91, 1500 Slowburban with 31 x 10.50 R15LT tires on it. I believe the rims are 16". I want to put the largest tire on it possible without going to a different rim and without adding lift. The local shops can't seem to come up with an answer to what size will fit and not rub the wheel well or cause some other problem. Anyone have any ideas.
post #2 of 9
31x10.50R15LT translates into a 31 inch diameter, 10.50 inch section width, and 15 inch rim diameter. The R is for radial and the LT is for light truck.

Your biggest concern is really rim width. Is there any way you can get the width of the rims the tires will be mounted on?
post #3 of 9
Thread Starter 
I believe the rim is 8 inches wide.
post #4 of 9
Just a couple thoughts...every increase in tire diameter will rob more power. It takes more torque to turn a larger diameter tire and even more additional torque in a soft material like sand. That also means more fuel consumption. If that's not a concern, don't worry about it. If it is a concern, I'd try to go wider but not taller, or maybe only one size taller.

There are also some specialized tires by Dick Cepek and/or Mickey Thompson that come in 13" or 14" widths at only 31" diameter or so. They would probably require wider rims, though.

Some tire manufacturers make a 31 x 11.50 in 15". That isn't a widely popular size, but I have owned some tires of that size before as replacements for 31 x 10.50 on a Bronco and a Ramcharger (Bridgestone Duelers). It's not a big difference in width (1"), but there is more rubber there to float out wider without increasing diameter.

To go up one size in diameter, those rims will no doubt fit 32 x 11.50 tires, and that is a fairly common size. I've done them on a Ramcharger before, also (General Grabber AP). I think you'd probably get the next size up - 33 x 12.50 - on those same rims, also, but that's probably the biggest. I can't speak for a Suburban specifically, but for the Ramchargers, even 33 x 12.50 will fit. The rears should be fine, and I don't think the fronts rub, at least not on the Ramchargers. Some of our state DNR's Ramchargers and military-surplus Chevy Blazers had that setup with Goodyear Wranglers in 33 x 12.50 15".

I just got a new set of tires for my '99 Grand Cherokee, and I got just about the largest size that would fit without rubbing...255/70/16. I wasn't sure about them at first, so I had the tire guys mount one and test it on the lift first to make sure it fit ok. The lift was the kind that didn't let the wheels "dangle" down as low as they reflected the normal position of the wheels. They turned the wheel all the way left and right, and the clearance was fine. So, I'd just have your tire shop do that...a bit of trial and error to see what fits the way you want.

My $.02. Good luck.
post #5 of 9
15inch rim? Probably a 265-75 would be safe, you might be able to squeek a 285 on there.
This forum is amazing and will surely help you out.

[ 07-15-2005, 12:56 AM: Message edited by: AMMODYTE ]
post #6 of 9
On an 8 inch wide rim, my personal preference is to stay with a 10.50 inch wide (or metric equivalent of 265mm) tire. An 11.50 inch wide tire might work, but any wider and the tire is being pulled in too much for my liking. A 12.50 inch wide tire really needs a 9-10 inch wide rim.

BeachguyDE said about the power, a general rule is for every inch in tire diameter the rear end ratio is reduced one-tenth. So, if the rear end ratio is 3.55 with 31 inch tires, then it would be 3.45 with 32 inch tires.

I looked at the fitment guide from National Tire & Wheel. Here are their maximum recommendations:

Stock: 31x10.50R15
2in. Lift: 32x11.50R15
3-4in. Lift: 33x12.50R15
6in. Lift: 35x12.50R15

There is a 33x10.50R15 tire made by BFGoodrich (and probably a few others) that might be worth a look. I am not sure if the width or the diameter is the biggest concern with GM vehicles.
post #7 of 9
Originally posted by Horse Shoe:
I believe the rim is 8 inches wide.
then I doubt they are OEM ...

I believe they all get 7" wheels ... I increased mine 94 to 8" W (16"dia) aftermarket and now I'm going to do it again and dump my 20" wheels/tires

I agree about getting a local place to experiment (like a shoe store), but whenever I've done that it was a place that charged too much for their tires in the first place.

Why not give tirerack. (you know what) a call and talk to a tech rep.
post #8 of 9
My 97 Z-71 has 285x75x16's on factory wheels ...not a problem.

post #9 of 9
Likewise, I run 285-75R16 on a 7" rim.

Important point, at least with BFG ...

The sizes like 31x10.5 are "flotation" tires.
They are designed to operate on reduced pressures.
When I told them that I run 12 PSI in my 285-75R16 T/A KO, they were adamant that I should NEVER go below 20 PSI. When I explained flotation and 10 MPH, they patiently let me finish my rant, and then explained that my "LT" tires were not designed to operate in flotation mode. There is more to tire parameters than dimensions.
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