4x4 Tire size difference allowance

I've tried searching the forums and Google, but I was wondering if anyone could tell me what tire size difference is acceptable for a 4wd. I've heard in general 1/2" or less in diameter discrepancy is okay. Obviously less is better, but hard to match sizes when only one needs replacement after 20k or so. Anyone know is 1/2 is okay or do I need to really try to find something exactly right?

 

Year? Stock? Lift?

 

Why can’t you find the size tire you need?

 

If you're talking about getting a new tire that's the same size and are worried about the other three being worn down, I would not be remotely concerned. The differential will make up for any size differences, I would think you could even go quite extreme (like multiple inches) for size differences without any issues ever arising.

 

I've always heard that it puts strain on the diff to do something like that?

My tundra is a 2010 on tires that are 255/80/17 on a 1.5" suspension lift. Not exactly a common size but I like the narrow tall tires for snow. I just meant after 20k on them, would it be advisable to throw a new single on when only one has worn uneven due to a bad alignment?

 

You’re fine. You’re talking fractions of an inch, possibly. If your other tires are that low on tread at 20k, it’s time to replace all of them anyway. The difference won’t make a difference.

 

Ideally they are all exactly the same size. But that is never possible. Turning the steering wheel while driving will put more strain on the 4x4 system than one tire being ½" different.

 

Cool so it sounds like it's mostly tire salesman blowing it out of proportion? Appreciate the feedback guys

 

there is a legitimate concern for spider gear wear in solid axle vehicles when the tires are mismatched. It never quits since the rotation is never equal…


I’ve been taught if you have a mismatched spare - best to run it on the axle with independent suspension if you have that option. Again though, talking different sizes - not a few 1/16ths of tread wear. It’s a differential issue - not really a 4x4 issue. You’d have the same concerns on a RWD truck.

 

I agree with running the miss-match on the non-driven axle. However, I think that this is more because of the potential steering issue that can result from one bigger and one smaller driven tires.
I also don't think that the spiders will wear out...... the spiders are 100% spinning as fast as possible on the front axle when in 2WD.

 

True - but there is no load when the spiders are spinning in the front diff since the driveshaft is disconnected.

 

This is an issue on awd vehicles because they would sense the fraction of a difference in wheel speed and try to compensate. On part time, especially when we are talking tire wear, give 'er.