4WD & Tire Question

[Triple J]

OK...here's one for all the automotive experts:

I got a flat on my Xterra this morning. Looks like its a razor blade, or a 1-2" flat piece of metal or something in the tread so apparently it can't be fixed...I need a new tire. Bummer, as the tires on the vehicle are only about 15 months old (~12,000 miles or so). They still have a LOT of life left in them.

The guy at the tire store is saying I should get 4 new ones because the tire diameter between the new ones and the old ones will be greater than 3/32", and I will damage my transmission/transfer case if I ever use 4WD for decent periods of time. Now, I can see needing 2 new ones, and keeping them either on the front or rear...but all 4 new? That seems like BS.  Seems to me tire inflation variation can cause more of a diameter increase that 12,000 miles of travel....but I admit I'm no expert and could be wrong.

So, what's everyone experience? Do I need 1, 2, or 4 new tires? Keep in mind, when I use 4WD it is mainly on the road (ya...I know that's lame) so it may be engaged for a while.

Thanks 

[Sinister]

I would say you need two.  What tire store did you go to?  Schwab's?  I only trust Les Schwab, with my tires.

[Triple J]

I would say you need two.  What tire store did you go to?  Schwab's?  I only trust Les Schwab, with my tires.

Ya, 2 I could see, but who knows.

Discount Tire. Les Schwab is WAY more expensive, and they only carry their brand. I  like BFG or Bridgestone for all terrain tires. I checked around on prices when I got this set and Discount was the best.

Discount has actually been great...they rotated and balanced the tires for free for me last weekend, and this repair would have been free. I'm just wondering if the guy knows what he's talking about.

[Bun-bun]

You need two new ones, and you need to get them from a different store.
I absolutely hate shit like this. Some douchebag is having a bad month, so he tries to up his sales thru deceit.
As a 4x4 owner since 1981, I can categorically state that the difference between new and 12k miles will never damage your transfer case or tranny. Period.











Oh, here comes my nurse with evening meds.

[Sinister]

I'm just wondering if the guy knows what he's talking about.

That's why I like Schwab's; I trust their guys...and they have great tires.

[silentbob]

Depends on the type of transfer case and the difference in tire diameter.  If you have a center diff in the t-case you will be spinning up the gears the entire time you are driving.  The circumference doesn't change based on tire pressure for a radial tire.  How much difference between front and rear is acceptable?  Hard to say.  My Hummer eats front tires much faster than rears and it never seems to bother the t-case.  Which is full time 4wd with a center diff.

[Speedbag]

I would say two at the most as well, but there can't be much difference in diameter at that mileage versus new.

If the vehicle has high miles and you can get one tire of the same brand and size I'd say screw it and just replace the one....

[LMT]

See if your tire shop has any take offs.  I have always got tires for my Jeep this way.  All the people that take off the OEM for something bigger save me a bundle of $.

[sno_duc]

Full size spare of the same make / model tire ?? If so... one new tire and the spare on an axle and the tire that was on that axle becomes the spare. 

[Popeye the Sailor]

Dang-sno_duc beat me to it!

[A.duc.H.duc.]

If it was me, I'd only replace the one. I like to replace my tires in sets of 4 when I do, so in your case, I'd buy the one, and then swap all 4 when the other 3 are due. Keep the 4th as a spare if you need it.

I've replaced a lot of tires, and I've never seen a diference as small as 3/32nds make a lick of difference.

Let's say you have tires which are approx 29in in diameter, I'm just guessing based on your vehicle. At that size you're only talking about a .644% difference in circumference That isn't much movement in the differential. If your truck has a 5 ft wheelbase, that would be like you 2000 ft diameter circle all the time. You won't see any decernable wear.

Justin

[Triple J]

Full size spare of the same make / model tire ?? If so... one new tire and the spare on an axle and the tire that was on that axle becomes the spare. 

That would be nice, but this is the 2nd set for the truck and these are a bit larger than the previous.

I think I may just get two and make the extra one the new spare so my spare is the same as the tires I have now. My OEM spare is a full size tire...but it's still smaller by a bit than ny current tires. Of course it may not fit up under the rear of the truck, so I may just get one.

If you have a center diff in the t-case you will be spinning up the gears the entire time you are driving. 

The circumference doesn't change based on tire pressure for a radial tire.  How much difference between front and rear is acceptable?  Hard to say.  My Hummer eats front tires much faster than rears and it never seems to bother the t-case.  Which is full time 4wd with a center diff.

How do I know what type of T-case I have? I have a mechanical lever inside (i.e. not electrical push button), but I don't have to lock the hubs.

May not matter...sounds like tire wear doesn't affect your Hummer though...which would seem to be a worse case with the center diff.

While diameter wouldn't change due to air pressure alone, wouldn't it change if the tire was underinflated so when it was loaded it squatted more and thus had a smaller effactive radius? 

That's why I like Schwab's; I trust their guys...and they have great tires.

I hear ya, but for a couple hundred bucks I'd rather call them on their BS, but still save the money. I used to have some Schwab Wild Country tires on my old Chevy 1/2 ton and I thought they were crap. 

Thanks for all the help guys! 

[the_Journeyman]

I'd say do what you want.  The difference between a worn tire and a new tire can't be *that* much.  At least not enough to cause a problem with the transfer cases.  Maybe if you were in 4-wheel on dry pavement or something but under normal use I'd think you'd be fine ~

JM

[Mother]

I fairly certain Silentbob's example only pertains to the + 10,000GVW vehicles. In a passenger vehicle the only thing that makes any difference is the diff, not the T-case. if you have open differentials then it is no big deal. if you have a locking diff then it matters what type, a clutch style locking differental will get hot much faster with the difference in tire diameter any other the clutchless type will simply eat up the tires. I used to be a Schwaby and things have changed, I do not like them anymore. 

[Triple J]

I fairly certain Silentbob's example only pertains to the + 10,000GVW vehicles. In a passenger vehicle the only thing that makes any difference is the diff, not the T-case. if you have open differentials then it is no big deal. if you have a locking diff then it matters what type, a clutch style locking differental will get hot much faster with the difference in tire diameter any other the clutchless type will simply eat up the tires. I used to be a Schwaby and things have changed, I do not like them anymore. 

Definitely open diffs.