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Tire width vs wheel width

Element

Element

1/2 ton status
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Mar 23, 2007
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Location
WV
Trying to decide on a new set of wheels and tires for the truck, but I've read a few conflicting things.

It seems like a 12.5" tire is ok on a stock-width rim for mostly trail use, as the pressure on the bead helps from losing it when wheeling at low psi. However, I have 12.5" tires on stocker wheels, and it seems like it's got a hell of a lot of sidewall bulge, and that worries me because 1 - it seems like that increases the risk of sidewall damage while 'wheeling, even at street air pressure, and 2 - it seriously detracts from handling ability on pavement.

I've been seriously debating tire size, and I don't really have a lot of experience with big off-road tires, so I'm not really too sure what to do. I'm currently running 35x12.5" tires on stock wheels. The truck has 6" of lift and some fender trimming, so I'm not too worried about going to 37" tires. What I'm not sure about is width - whether I should go with 37x12.5" tires, or bump the width up to 14.5" or 15.5". Truck is daily-driven, and will see mostly mud and regular trails, no rocks, once it's suitable for hitting the dirt. Older guys like my dad tell me skinny tires are better, as it allows you to cut down through mud and snow to bite into terra firma. Other people advocate wider tires for better flotation in mud, and a bigger contact patch.

Just want to get a bit of insight from experienced people before I drop $1000-1500 on new wheels and tires.
 
IMHO a 12.5" wide tire looks better on an 8" wide wheel. The factory aluminum wheels are 7" wide and they work good on those also. If you decide to go with a 14.5 or even a 15.5" tire then i would definately step up to a 10" wide wheel. Just remember that the wider the wheel is and the more offset it is the harder it is on bearings and other outer suspension parts like ball joints if you're running a D44 or 10 bolt axle up front.
 
4X4HIGH said:
IMHO a 12.5" wide tire looks better on an 8" wide wheel. The factory aluminum wheels are 7" wide and they work good on those also. If you decide to go with a 14.5 or even a 15.5" tire then i would definately step up to a 10" wide wheel. Just remember that the wider the wheel is and the more offset it is the harder it is on bearings and other outer suspension parts like ball joints if you're running a D44 or 10 bolt axle up front.
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Well, the 1/2 ton axle will be gone as soon as I can find anything on this area, or possibly in December. I won't be getting new wheels and tires until then, as I don't want to have to deal with trying to sell a set of 6-lug wheels and buying 8-lug for the new axles.

I'd honestly prefer 37x12.5" tires, as I like the looks of them more, but I wasn't sure if there was a disadvantage to running skinnier tires compared to wider ones. I know the holy grail of tires is the biggest bogger that'll fit, but I neither want nor need something like that. Just trying to narrow the selection down a bit.
 
12.5" = 8" rim
14.5" = 8-10"

That is the way I see it and run it. Running the narrower rim will help keep the tire on the bead better offroad. If you are running big tires offroad only then I would run 8's also for the same reason unless you go beadlocks.

Also if you decide to do weld on bead locks it adds 1" to your rim size so 8's are now 9's and 10's are now 11's. Unless you are running a super fat tire 11" rims or bigger isn't optimal for offroad use.

Harley
 
What he said...they said.


Nice to be on a 4x4 forum again where a discussion like this doesn't devolve into mall queens talking about the "deep dish" effect of 15x10's...:rolleyes:


Just from my year experience of running 36x12.5-16.5 tires on 16.5x6.25(?) factory wheels yes that width of tire and wheel will work pretty well. Handling wasn't bad, wear was good, and it's the original redneck beadlock.
However if you still have push pull steering the ballooned out sidewall may hit the forward drag link end when turning hard to the right.
For that reason only I say if you have factory push pull steering go with some 8" with about 4" of backspacing. That should keep the sidewalls off of the drag link nicely.
Whatever you do definitely test fit a tire on the driver's side and see that it clears the steering.
 
all i've read, on road the wheel can only be 4" smaller then the tire

i have a review on 37"x14" iroks, liftedtalk.com/review.html
 
I have 37x12.5x15 MTR's on 15x8" wheels. They are 4.5" wider so they can't driven on the street? I am sure 50% of the people on this site are running 12.5" wide tires on 15x7 or 8" rims so they can't drive on the street either?

90% of the guys I run with in AZ DD or did DD there trucks with over 4" difference in tire vs. rim size.

4" may be a rule of thumb for some people but it really isn't a good rule.

Harley
 
I ran my 37/12.50 MT/R's on an 8" wide wheel and I thought it worked fine.

I now run my 42/14 IROK's on the same 8" wheel and I have no complaints. The wheels will be wider ~1" when I put beadlocks on them this winter.
 
I really doubt that the difference between an 8 and 10" wide wheel would "seriously detract" from the handling on the street. Since it doesn't sound like you have directly compared the same truck setup with the exception of the wheels, but I'm guessing narrower tires but much shorter and stock suspension?

My DD has the stock 6.5" wide wheels with 285/75 tires (11"+ wide) and I've noticed no handling changes as compared to the stock 245/75 tires (9.5" wide). My trail truck has 15.5" wide tires on 8" wide rims, and several other guys in our club have similiar setups. In my experience the narrower rims actually protect the sidewalls more and keep the bead much better. My previous tires were 13/38 TSL's on 10" wide rims and while I never had an actual sidewall tear, the sidewalls definitely looked more beat up (cuts down to the cords, etc...) than a buddy's truck with the same tires on 8" wide rims.
 
im running 15 inch wide tire on a 10 inch wide rim with no complaints. I dont think it has to much bulge and the bead is definately seated good. I dont have any issues when airing down at all. I ran a 13 inch wide tires on a 7.75 inch wide rim for a long time and no issues what so ever.When I go up to colorado to hunt my buddy gives me so much crap for running such wide tires. Skinnier tires definately get down to the bottom of snow much quicker and feel much more planted. In gooy mud I like them a little wider and they have a little bit bigger foot print on the rocks but I really doubt it makes that much a difference. So I think its persoal preference really, I like the extra width and for some reason its just feels more stable to me.If I was running anything smaller than 38's I would only run a 12.50
 
all i've read, on road the wheel can only be 4" smaller then the tire
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on my k5, my 33x12.5s are actually 13" wide (company specs and i measured to check) and i run them on and off road on 8" rims. handles well, for a 25 year big truck.

as far as mud goes, i like floatation better than digging. if i had taller tires, maybe i'd think otherwise, but i hate digging in and hanging up the axles. doesn't happen to me much, but it's pretty much the only thing that's ever hung me up. it depends on what type of mud, too. soupy mud with a solid bottom is fine to cut through. but we have a lot of thick clay mud here that holds deep ruts. once the axles dig into that heavy row of clay between the ruts, you're SOL.
 
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