Will mis-match tire sizes burn up 4x4??

fifthand · Dec 20, 2008

Hello,

I had someone recently tell me that running mis-match tire sizes will ruin the 4x4 system in hurry. I do not have mis-match sizes but I do have different brand tires front to back. When I bought the truck the front tires were toast but the back were fine. One of the back tires has slightly more tread than the other but are otherwise identical. The front tires are of a different brand but the same size as the back. Shoud I be worried about running the truck in 4x4, considering the front tires are new and may be slightly "bigger" than the back?

NVW · Dec 20, 2008

Slight differences shouldn't matter. When you have mis-matched tire sizes is when I would worry.

Green Machine · Dec 20, 2008

rear tires must be the same with the same amount of tread on them, because if one is smaller then your gears in the rear end are turning way to much then they need and you will burn up the rear.

Running same size tires are important when you have 4x4 engaged and have traction, it "could" bind up some stuff in the T-case. I'm no expert though :/ just what makes sense to me

edzzed · Dec 20, 2008

i don't think mis matched tires will mess 4x4 however, it is more about the tires circumference and or diameter if you know what i mean. Ed

mitchedo · Dec 20, 2008

As long as you're using your 4x4 in slippery conditions only (rainy asphalt is NOT slippery enough), then it shouldn't matter. The slippery surface will allow the tires to slip. It's really no different from making turns with the center diff locked. If you're using your 4x4 on pavement, you're causing great stress to the components. Period.

This applies to part-time 4x4 only. If you have a viscous center coupling, then be very careful with your tire sizes. ...though even that isn't terrible if one's a little out.

As mentioned, I'd be more concerned with running mis-matched tires on the same axle than front to back. ...assuming you're not driving around on pavement with your 4x4 engaged.

will92104 · Dec 20, 2008

I have been told that different size tires will mess up the gears in the differential because the smaller wheel is spinning faster than the bigger one. never tested it but it makes sense. i would say that as long as the tires have the same size stamped on them but wear is different then it should be no problem. I have ran mismatched tires but the same size and had no problems

fallout · Dec 20, 2008

fifthand said:
Hello,

I had someone recently tell me that running mis-match tire sizes will ruin the 4x4 system in hurry. I do not have mis-match sizes but I do have different brand tires front to back. When I bought the truck the front tires were toast but the back were fine. One of the back tires has slightly more tread than the other but are otherwise identical. The front tires are of a different brand but the same size as the back. Shoud I be worried about running the truck in 4x4, considering the front tires are new and may be slightly "bigger" than the back?

Without knowing what exactly your drive train set up as long as the sizes are within .5-1 inch of each other you should be alright the slack in your drivetrain will allow for a variation of this much. Running different gear ratio's or substantially different size tires can cause your chain driven transfer case to go boom. as it is usually the weakest link. That being said I have a buddy that races in the mud bogs and he has 5.13's in the front axle and 4.10's in the rear, But the only time it is in 4 wheel drive is in the bog, and he still finds away for finding the weak link in his drivetrain usually with a big boom and grinding.

modified · Dec 20, 2008

As said, drive on slippery roads and your tires will slip as needed.
If you were really concerned, even if all tires were the exact diameter, improper air inflation will offset tire diameter from front to back.
To match tire diameters as close as possible to minimize drive train binding, measure the rolling radius or each tire installed on truck, (center of axle to ground), and inflate tires as needed to match them. First inflate front tires to the required 55ish PSI, and then inflate rears to match.
If altering weight in rear of truck, to rolling radius will change accordingly.

Dracor85 · Dec 20, 2008

running diffrent size tires on the same axle will mess with more than your 4x4 system. over the summer I had a set of 265/75/16's on my truck and ended up with a flat. my spare was a 245/75/16. it messed with the brakes, making the brake with the shortest tire work the hardest. also I had to use the 4x4 on some wet grass and even with the slippage of the grass you could still feel a skip every so often. that being said if you have the same size tires and one is more worn than the other i would say no to worry about it to much, but to be on the safe side dont run around with the 4x4 on on dry pavement as stated above, expecially if you have a posi or even worse with a locker.

heymccall · Dec 20, 2008

Alright, to expound on what modified posted. Running mismatched tires (regarding their rolling diameter) will cause excessive binding in the 4wd components, namely the transfer case.
To check rolling diameter, with the truck on level lot, mark a line at the bottom of each tire (on the sidewall) (tape or wax pencil), and roll (drive) the truck forward for 10 tire revolutions as seen at one left side tire 'til the mark is at the bottom again. Any mark on the other 3, that is off by more than an inch, indicates a rolling diameter variation beyond acceptable, and it must be corrected to ensure the continued reliability of the 4wd components.

fifthand · Dec 20, 2008

heymccall said:
Alright, to expound on what modified posted. Running mismatched tires (regarding their rolling diameter) will cause excessive binding in the 4wd components, namely the transfer case.
To check rolling diameter, with the truck on level lot, mark a line at the bottom of each tire (on the sidewall) (tape or wax pencil), and roll (drive) the truck forward for 10 tire revolutions as seen at one left side tire 'til the mark is at the bottom again. Any mark on the other 3, that is off by more than an inch, indicates a rolling diameter variation beyond acceptable, and it must be corrected to ensure the continued reliability of the 4wd components.

So you guys are talking no more than 1" of variance on circumference? If so, I would think that is possible with the same size tires unevenly worn. Are certain sides of the axles, front-to-back, more critical? Example: left front must match right rear as closely as possible? I do have a locker final drive. How concerned do I need to be about the two back tires not being exact? Thanks.

Edit: Again, the back tires are the same size/brand/model. It is just that one of them is visibly more worn than the other.

ghitch75 · Dec 21, 2008

if you go from say 265 on the front and 305" on the back....put in hi-lock and you could get e transfer case in your cab...

wagonwheeler · Dec 21, 2008

I wouldn't be terribly concerned if they are just worn a bit different from each other. The difference between the two is just causing the planet gears to turn ever so slowly to make up the difference when driving along - like taking a turn with a 2 mile radius.

Most side gears and planet gears ride on thrust bearings and as long as you have plenty of lube they can take the movement in stride - because there is not much movement except in actual hard turns. Roller bearings can take even more speed of movement.

Think about how much spinning those thrust bearings take when people cut the wheels and stomp the accelerator to get tire spin - if only the inside tire is spinning the thrust bearings on the planet gears are absolutely screaming. But they can take it. They take the movement on every turn you make every day for thousands upon thousands of miles and they spin faster then than due to a minor tire size difference.

Full time 4wd splits driveline windup through 3 differentials. Part time 4wd can actually get more driveline windup when running in 4wd since there is no center diff.

But even running in 4wd with tires aired down on bone dry slickrock in Moab and wheeling hard in low range just causes LOTS of tire wear - driveline windup typically releives itself by slipping tires as it has the mechanical advantage to do so.

Chaser

wagonwheeler · Dec 21, 2008

Are these tcases really that weak? I've alway run geared cases but have never had a problem even w/ front and rear lockers on a part time 4wd locked in for days at a time on slickrock (which has more grip than asphalt).

I've seen cases blown because of improper thrust clearance, low lube, etc... But not from driveline windup.

Chaser

ghitch75 said:
if you go from say 265 on the front and 305" on the back....put in hi-lock and you could get e transfer case in your cab...

ghitch75 · Dec 21, 2008

try it with say 3.73 gears in the front and 4.10's in the back....TC wouldn't be happy!!!...seen bad things happened when i was a kid 4 wheelin' in the woods....with different tires size on trucks.....we where poor and put what ever we could get to get in the mud!!!...

modified · Dec 21, 2008

fifthand said:
So you guys are talking no more than 1" of variance on circumference? If so, I would think that is possible with the same size tires unevenly worn. Are certain sides of the axles, front-to-back, more critical? Example: left front must match right rear as closely as possible? I do have a locker final drive. How concerned do I need to be about the two back tires not being exact? Thanks.

Edit: Again, the back tires are the same size/brand/model. It is just that one of them is visibly more worn than the other.

heymcall stated more than 1" of variation in 10 revolutions, which is equal to 0.100" of circumference variation.

As for your rear locker and your rear tires not exact diameter, the way I understand the G80 reading on this site, the G80 rear locker is designed to lock when rear wheel RPM's differ by >100 RPM's, and unlock at speeds >25 MPH.

Will mis-match tire sizes burn up 4x4??

fifthand

NVW

Green Machine

edzzed

mitchedo

will92104

fallout

modified

Dracor85

heymccall

fifthand

ghitch75

wagonwheeler

wagonwheeler

ghitch75

modified

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