danjr2010

So I have some 265/70r17s on my Cherokee right now. The back two are pretty worn, and a buddy is giving me three good 255/75r17s. From what I understand the tires my buddy is giving me are larger by about .5" Is this right? Can I run the 255s in the rear and the 265s in the front? Obviously in 2wd it won't matter. But in 4x4 is this bad for the transfer case or any part of the driveline? I don't run 4x4 on pavement, only on offroad.

Thanks for the help!

Woody32

I believe the new ones will be more narrow than what you have now. There is a very specific math problem involved, and honestly math is not my strong point. However, having run two different sized tires on a 4x4 before I put the bigger tires in the front.

mud-dog27

it can be done, but it shouldnt be.

having 2 separate sizes on the same axle will cause the differential[open] to go crazy as one tire will be going faster than the other, like your cornering causing added wear as it tries to compensate and figure **** out.

if your running lockers issues will be similar

265/70/17 = 31.6x10.4/17


255/75/17 = 32.1x10/17

OOdynamite

He's not running 2 different tires on the same axle, he's running different size tires upfront then in the rear.

But either way, it's bad. I wouldn't put it in 4wd, the smaller tires will want to turn faster then the bigger ones, and your tcase will not take kindly to that.

mud-dog27

my bad i didnt catch that, thought he ment he was going to run 3 of one size then one of the other, but either way i wouldnt advise it but as long as you dont run it in 4wd i dont see it causing any issues just have a bit of a rake.

OOdynamite

Oh haha, yea, that would be real bad.

ktmracer419

i wouldnt want to do it with a chain driven transfer case but ive competed with a rig that ran different gear ratios in each axle successfully and reliably. but the half inch you are talking about is the difference between new tires and bald tires. even less. i wouldnt worry about it.

Gorillaxj

I wouldn't do it on a 4wd.

danjr2010

Thanks for the info guys. I will Not be running different sizes on the same axle haha

danjr2010

That's what I was thinking. The difference is so small that its no different than having two worn and two new. Plus if its offroad tires can slip a very minute bit if necessary

eastonarcher1993

Not advised but as earlier said bigger up front. I just would keep em all the same size

RenegadeT

I'd try it. First I would measure the tires, see what the actual diameters are, or at least set them side by side.
Another point to consider is the axle gears...they are never exaclty 2 digits (ie 4.10), some axles are 4.11, etc., it depends on how many ring and pinion teeth. There is some rounding off there.

90xjcjf

If I'm not mistaken the 255's r smaller. The first number should be the height and the second is the width. Well from what I have been taught but I'm not an expert. U should be fine running two of the same on the front and two of the same but different than the front on the rear. U just don't wanna run two different on the same axle.

danjr2010

The second number is actually the aspect ratio I think, either way it changes the height from the rim edge to the outside of the tire. like a partial radius if that makes sense. Idk how it works exactly, I just found a site that you could plug in the size and it compared them. The 255s are slightly taller, yet narrower.

Dan91

Metric sizing works like this (it's pretty ridiculous)

The first number is the width of the tread in millimeters
The second number is the sidewalls height as a percentage of the first number
The third is the rim size

So...a 235/75/15 is 235mm wide and the sidewall is 75% of 235mm so the height would be the sidewall measurement times two plus the rim size (don't forget to convert your units so they are the same!!).