What Tire Size ?

GMC-AT · November 22, 2014

I have a GMC AT right now with 275/55/20. I have a 2in level up front. My question.. If I want a tire that is a littel bit taller.. and a little bit wider.. what would be the perfect size?

My AT rims get curbed real easy... I would like to get a tire that is a little wider to protect them better. Also a little taller since I have a 2in level...

mafd2 · November 23, 2014

285/60/20 a little taller and wider but is all terrain. 275/60/20 is taller but about same width.

Panik · November 23, 2014

I can't answer your question, but this might be fun/helpful to play with if you aren't already aware of it:

http://tire-size-conversion.com/tire-size-comparison/

The page has a pretty neat visual comparison feature.

GMC-AT · November 23, 2014

Ok.. so If I go to a 285 .. the tire will be about 1.5 wider according to the chart ... my question is ,.. will this extra 1.5 in actually protect the lip of my rims any better ?

If not.. I will just get a 275/60/20..

Mojado · November 23, 2014

I have the All Terrain with a 2.5" level. Been thinking about getting the 295/60/20. I was just going to go to discount tire and ask them about trying it out to test and make sure there is no rub or anything. I haven't had issues with the stock tires not protecting the rims though.

Mojado · November 23, 2014

Thanks Panik for the little chart, cool visual. I think the 285/65 might give you what you are looking for, that's probably what I will try out in the KO2's

blackout07 · November 23, 2014

Ok.. so If I go to a 285 .. the tire will be about 1.5 wider according to the chart ... my question is ,.. will this extra 1.5 in actually protect the lip of my rims any better ?

If not.. I will just get a 275/60/20..

No it won't. The tire width won't do anything to protect the lip. Certain tire manufacturers like Nitto make their tires with a lip protector. The sidewall actually protrudes past the lip of the wheel by a about a quarter of an inch. That is what you need to look for.

GMC-AT · November 23, 2014

Cool... do you guys know any other tire makers that may this?

Spurshot · November 23, 2014

The OEM tires are all around 31.5 or so. A 33" (actual 32 1/2" on most ) works out nicely.

The width of a 285 is 10mm wider than a 275. 10mm is about 3/8" . This is the "Section width", which is not the tread width. It's measured across the shoulder of the tire.

A 33" x 11.50 fits into the well easily Push it up to a 33" x 12.50 and it gets pretty tight and wheel offset gets important. You can trade a little width and put a larger diameter in the well without rubbing. Someone had some 34" tires in a leveled truck. My recollection was that they were something like 275s.

An interesting fact is that increased diameter works better in soft terrain (sand, loose dirt, mud) than an equivalent contact area (wider) in a shorter tire. It has to do with the entry angle of the tire to the ground. Honda's skunk works did a bunch of testing many years ago on this and a friend made some test rig for the project. Hence the reason dirt bikes all went to tall front tires long ago, and why a minibike steers like crap in sand (LOL).

redwngr · November 23, 2014

Larger diameter also gives a 'longer' footprint for the same tire width, resulting in greater contact area, therefore less lbs per sq in.

Panik · November 24, 2014

Cool... do you guys know any other tire makers that may this?

I just picked up a set of Hankook ATM RF10's in LT275/65R18:

I bought them because I wanted something in AT flavor that wasn't too aggressive and was a good all around tire. Apparently I got lucky because at least the LT variety comes with rim protection.

So far I love'em. Haven't run them on snow or ice yet, but in dry conditions and heavy rains they work well. If I remember correctly they might be right at or just shy of 50lb per tire in the size I purchased. I may have lost about .5 to 1.0mpg going up in size and weight. Still not sure about it because: A) temperature dropped significantly and stayed down right after I got them and B) I haven't reprogrammed the computer to compensate for the size change.

I'm sure if you look around there are probably plenty of AT/MT tires that have rim protection. Good luck.

Mojado · November 24, 2014

Cool... do you guys know any other tire makers that may this?

I had the BF Goodrich all-terrain KO on my old truck. They had a little lip that protruded past the rim. I remember it being annoying when I was plasti-dipping my rims!

Big Whiskey · November 25, 2014

A lot of guys have been running 285/55/20's and 295/55/20's on their stock rims with 2"-2.5" leveling kits. They're both a little taller and a little wider than stock. A 275/60/20 or 275/65/20 will also work, but they're the same width as stock, just taller. The first number is the width of the tire in millimeters. The second number is the height of the sidewall, expressed as a percentage of the tire's width. So, on your stock tires....they're 275mm wide, and the sidewall height is 151.25mm (55% of 275). You need to take both numbers into consideration when deciding on tire sizes. For example, a 275/65/20 tire is much taller (but skinnier) than a 305/50/20.