Waylayer

Picked up some somewhat new tires, they are studded and plan on running them in winter. They are Kelly Safari MSR's in two different sizes, two are 255/70/r16 and the others are 245/75/r16. The 245's are .4" taller and alot more narrow. Was going to get another two matching tires but cant find these anywhere. Thinking of running them, if so I plan on putting the wider shorter ones on the back (because they are wider) at full air pressure. Then run 245's on front aired down to compensate. Am I asking for trouble here? If anyone can find these tires in good shape let me know.

Black_1985_SR5

iTrader: (1)

Most definitely dont do that in 4 wheel drive you will bind some stuff up

Waylayer

Should be good running same size tires but similar tread pattern then? Done that on cars before, but they were just beater rigs so it didnt matter. Kelly has the Safari TSR tire that is a similar tread pattern.

Best thing to do is try to sell em, made a bad move buying them in the first place.

niall

.4" is nothing to worry about, you're truck isn't "AWD" in the sense that you're not running a torsen/haldex/load sensing center differential.

Hell, you can run two different gear ratios within reason (not on dry pavement, which you shouldn't be running 4wd anyway).

Waylayer

255's are 30.1" tall and 245's are 30.5" tall. The 245's are worn a little and 255's are about new.

could always throw the 245's on back on someone elses truck and have em roast em for a bit to skim some of that size off. ha.

snobdds

You'll be fine. That's nothing.

dropzone

iTrader: (6)

circumference is what comes into play, as in measured rolling distance.
circumference is 3.14 (p) times the Diameter

Black_1985_SR5

iTrader: (1)

I wouldn't do it in 4wd on pavement no matter what all it takes is that one patch of traction

Jake_D

dont run it in four wheel drive, it wont do anything right away but over time you will end up doing a couple thousand dollars in damage. you can run two diffident tread patterns that are the same size, for some reason people think that all of your tires have to be the same tread pattern.

niall

All of this "don't run it in 4wd" is nonsense.

Seriously, follow normal 4wd rules, ie. don't drive in 4x4 on dry pavement, and you will be ABSOLUTELY OK.

I dare everyone to go out and measure their tires, I guarantee quite a few people's tires amount to more than .4" difference from normal wear.

The only vehicles that it is critical to keep tires of the same rolling circumfrence are ones which have torque sensing center differentials/transfer cases, as the fluid in the center differential carrier is usually a thick silicone based fluid that easily burns up.

.4" amounts to one being 1.33% taller than the other. Or a 1.33% difference in rolling circumfrence. It will not matter.

Run those tires and be happy!

Waylayer

How different would it be from matching tires catching traction? The truck doesnt have any locking diffs. Not exactly sure what would go wrong. Guessing that the smaller tires would spin a hair faster.
Also would it make a big difference whether in 4h or 4 low?
Ive driven this truck alot on bad paved winter roads in 4h, headed too, 50-60mph. Also 4L hauling a massive amount of weight and freighted trailer. Only way it would make it up hill was 4L. Matching tires though, but still putting a test on gearing.

YoungFeller

I also wouldn't worry about that size difference, as long as you're using 4wd only on slippery surfaces. It doesn't matter if it's high or low range.

It turns out that the same tire size from different manufacturers often varies more than that. Just like clothes, some tires run big. Others run small.

Waylayer

Going to get them mounted and get back tires at 35 psi and run fronts lower, going to test out what a good pressure is, there is an added leaf so shouldnt be noticeable. The truck is getting rebuilt with 22r, lift and going to be running 33's when ol man winter doenst have a choke hold on, no more hauling heavy loads with it either, getting rid of beast of a trailer I was using and rebuilding a smaller one to use. Going to have to try to take it easier on this ol girl... thanks for the input on running these.