31's on '92

[|SkidRow|]

I've been trying to make a pros and cons list for getting 31's on my '92 XL and I can't think of very many, so I thought I'd ask here.

What I have now is:
Pros: Slightly less prone to rolling.
Better traction(newer tires in the northern winter)
Highway MPG will increase(am I correct on this?)

Cons:
City MPG will go down(Only slightly?)
May or may not rub, got mixed results with a search.

I currently have 235/75/15, which comes out to 29/9.25/15 metric and I have the stock rims, 15/7. The tires I am planning on getting are the Goodyear Wrangler Territory M+S Tires, they have a rather aggressive tread, compared to the tires I have on now. If I went with 235/75/15, they would be $20 cheaper than the 31's.

235/75/15-$80ea, 2nd tire 50% off (so buy 3, get one free.)
31/10.5/15-$102.89ea.

And these are listed as LT, not P tires, will I be ok with getting the LT's? I will be checking what gears I have when the sun comes out and will edit my OP.

Also, my roommate has 31's on his '94 and they don't rub at all and they didn't off set his speedo, by very much, maybe one or two km/h (0.6-1.2 MP/H)

Any and all answers would be greatly appreciated.


|SKidRow|

 

[gt fast]

ok let me see if i can help you out. i drive a 92 explorer 4 door 2 wheel drive. stock size was the same 235/75r15 on the stock wheels. i have 31x10.50 15's on my truck and it does alot of good. highway miles didnt change for me in gas mileage, but the city does drop just slightly,1-3 miles per gallon. the only time my wheels rub is during a hard u-turn, but it is a very slight rub. the inside tread just barly grazes the sway bar up front. i bottom my truck out almost every day and it does not rub the fender wall. i have the goodyear wrangler authoritys on and they are a real aggressive tread pattern. they run anywhere from 120-150 a tire. the road noise is slight traction is good and no noticeable body roll from the tires. hope it helps

 

[gt fast]

oh and im not exactly sure but i do believe the 31's made my speedo off by 5 miles per hour. but im not exactly sure couse it may have been off when i bought it.

 

[Anime]

31's don't make it any less prone to rolling than 235's, since the slight width increase is offset by the slight height increase, raising the Center of Gravity.

Because of the narrower width, the 235's are usually "better" in the snow, but 31's sometimes have slightly deeper tread, so it kind of depends on the tire. The wider 31's do give better flotation on other surfaces, though.

Highway MPG usually stays the same or decreases, since even though they are larger diameter, the heavier tire takes slighty more gas to turn, and the wider tread gives more traction, and that means friction. Softer tires compound this even more, so a softer All-Terrain 31 will get lower mileage than a All-Season 235.


31's will usually rub on an all-stock suspension since it's usually sagged over time. You can either get new springs for the front or use some washers to raise the front end 1/4-1/2" back to stock height, which can help take care of the rub at full lock.


I'd say really it comes down to gearing. If you have 3.08 or 3.27 gears, it will put more stress on the tranny, especially an automatic, and it will be a lot slower than with 235's.

If you have 3.73 or 4.10 gears, then 31's will be just fine.


Keep in mind there are also 30 x 9.50 tires, with about a 29.5 inch diameter, just a slight increase over the 235's and slightly smaller than the 31's. These usually offer the deeper tread and look a bit bigger, which is good for rides with higher gears that might not be suited for 31s.

 

[XLT]

I went from 29s to 30s on my 93 and noticed my speedo off by enough. Speedo said i was doing 65mph but i was really doing 72mph. Also confirmed by a state trooper. I lost about 1mpg as well. The only other con from bigger tires was that it felt like i was running my a/c when accelerating. So just a little power loss. I had 3.27 gear but i would still get bigger tires again.

 

[|SkidRow|]

Alright, thanks guys, I think I will just stick with the 235's as they do have about a 1/2" tread and that does make them look a lot bigger than they actually are. Now I'll have $60+ to spend on something else :

Edit:
Just checked, I have Axel Code 41- Open 3200 3.27 gears. I think that shows I should keep to the stock tires right now, until I can upgrade the gears. Also, since the GY Wranglers are LT rated and not P, they are going to be heavier and still add a bit more stress on my tranny? Will I be ok, or should I try and find a P rated tire?

 

[|SkidRow|]

I found someone locally selling a set of 3.73:1 gears for an 8.8 Ford, what the max tire size I would be able to go with those? I'm not looking for something too big, just something bigger than stock. This is all happening down the road as I'm off to Quebec for six months pretty soon. No lift yet, either

 

[Jason94sport]

They would work well with 31's.
Problem is if you want to use your 4WD you also need to re-gear the front.
Biggest problem I had with 31's was the drop in performance. I had no power.(3.27's)
I'm keeping the 235's on my current X.

 

[bats]

If your gears are not at least 3.73 you feel a noticeable performance hit. Spedo will be off slightly and out of the hole will not be as responsive. Ideally you would roll with 4.10's to keep it around stock performance.

 

[fishnhunt18]

I have 31x10.50x15 Pegasus Advanta AT on my 92. They went on while stock, but I have since lifted it about 2.5 in. I noticed when I changed from stock tire size that it wobbles a bit more at highway speeds. Depends on whether you're going for looks or practical drivability and fuel economy.