Tire damage question

[earp73]

Go figure. I drove to AK and back via the Cassiar Hwy. - twice - and never had a flat. We go out for a family camping trip this weekend up near Lake Almanor in CA and I get one. We were on a freshly graded dirt road with a fair amount of rock. One of the sharp rocks from the grading was surely the culprit. The tire was blown with a gash and might be beyond repair.

I changed out the spare, which is a GrandTrek that came with the rig and drove on to our destination. My question is this...Is there any concern with running a spare with more tread and of a different type than the other three that is the same size?

This may be a stupid question, as somewhere from my memory banks my mind tells me it's a bad idea. I am in need of a new set of tires, not desperately, but by winter. I wanted to postpone the expense until then, but if there are negative ramifications (drivetrain or?) I'll bite the bullet.

Thanks in advance for the input.

[breathed]

Running different sized tires is is not a good idea. When moving in a straight line one tire will be rotating more or less than the other three.

I have no idea, however, how much difference in size or distance driven will cause harm.

[e9999]

in principle it's a bad idea if you're gonna lock things up.
In practice, the diffs and the VC will probably handle a slight difference for a while if you keep it unlocked, I would think. Say 1/4" tread wear out of 33", you're talking only 1% difference in rotational speed. I doubt the VC will start boiling up quickly with half that much slip. Then again, I would not run it for long on the freeway that way myself, simply cuz I'd rather not take the chance. But coming back from a trail that way, I would not hesitate. May stop once to let things cool down just in case, though.

Now, if the spare is a different size altogether (say 31" vs 33") now you're starting to talk problems...

and obviously, if the type is completely different (street vs Mud) you're talking traction, handling, and stability issues (I would not do that in rain or snow for sure)



Oh, and anything that helps you get rid of GrandTreks is for the better...

[Tools R Us]

I have zero problems with that wear difference. Mine is much more severe, like new tires on the front, 1/4 tread on the rear and they are 37" muds, so a much greater size difference. Had no problem with locking them dozens of times in the ~300 miles of off-road travel on the Utah trip a couple of weeks ago.

[hj60]

C'mon guys, do you think Toyota engineers really thought wed be running under ideal conditions all the time? That's Dodge. Sheesh.
We replace single tires all the time on our fleet trucks. Some have LSDs, to boot.
Whatever's cheapest and available at the time usually, as it's a road call. And the road service guys don't always get it right. They mix brands, load ranges, traction vs steer, you name it. We've yet to have a single diff fail.
Planned tire changes are always done in pairs, but unplanned ones are far more common.

[e9999]

keep in mind the size difference only matters when locked, of course, and perhaps with a LS. If you have open diffs everywhere, you can run 33" on one side and 20" OTO with no problem except perhaps hot oil in the diffs.... (and attract unwanted attention from low riders on the one side.... )


added: OK, obviously, when I said "when locked" I meant "when locked on asphalt"... not on low traction surfaces where there is no issue, of course....

[Tools R Us]

Originally Posted by e9999

keep in mind the size difference only matters when locked, of course, and perhaps with a LS. If you have open diffs everywhere, you can run 33" on one side and 20" OTO with no problem except perhaps hot oil in the diffs.... (and attract unwanted attention from low riders on the one side.... )

The biggest "problem" as it relates to the FZL80 is the viscus coupling. If you run different size tires, front to rear, it can overheat and die. The question is, how much difference does it take to cause damage?

Running 33" on one side and 20" on the other would likely wear out the spider gears in short order. If lockers are properly used their a zero issue. Lockers are used when one tire on the axle has lost traction, so with that tire slipping, spinning it doesn't matter what size it is.

[e9999]

Originally Posted by Tools R Us

The biggest "problem" as it relates to the FZL80 is the viscus coupling. If you run different size tires, front to rear, it can overheat and die. The question is, how much difference does it take to cause damage?

Running 33" on one side and 20" on the other would likely wear out the spider gears in short order. If lockers are properly used their a zero issue. Lockers are used when one tire on the axle has lost traction, so with that tire slipping, spinning it doesn't matter what size it is.

yes, I mentioned the VC a bit above, here I said "open diffs"

the 20" was a euphemism, of course, but why do you think the spider gears are so delicate anyway? Just smaller? I mean, heck, you got gears everywhere in your TC and trans and they're good for 200,000 miles....

[Tools R Us]

Originally Posted by e9999

...
the 20" was a euphemism, of course, but why do you think the spider gears are so delicate anyway? Just smaller? I mean, heck, you got gears everywhere in your TC and trans and they're good for 200,000 miles....

Spider gears only turn to allow different tire speed, this is normally only a couple of revolutions as the rig turns, then are mostly stationary. They aren't designed, or have bearings for high speed or constant operation.

[e9999]

Originally Posted by Tools R Us

Spider gears only turn to allow different tire speed, this is normally only a couple of revolutions as the rig turns, then are mostly stationary. They aren't designed, or have bearings for high speed or constant operation.

fair enough, I was being facetious.
Anyway, forget the 20" bit, I would not worry about differences in tread with an open diff.

[jaymundy]

Short answer to your question: The small size difference from worn tread vs new tread given the same basic tire size (and design) shouldn't cause you any problems.

[douglashuft]

Long silly version:This is why we need twin sticks and all four selectable hubs . Stick the mismatch on the rear (where it will be less of a steering issue) freewheel the rear hubs and use the twin stick to select the front axle only as a drive axle. Or more realistically, pull your front axle, drive plates and lock the cdl and run the mismatch on the front. If it were me, I would just drive on them as is with the "funny tire in the rear". I will admit that I just bought 5 tires for my rig and rotate them all in order to avoid this "problem". Of course 5 tires only works until you destroy one tire and then you still end up with a newer different tire.
Short version: Dont worry about it.