Spare Tire Question

[StarsnBars]

Morin all, Great spring day here in the midwest. I upgraded my tires to 35's except for the spare. Its a 33. Question,,, Will a smaller tire hurt my driveline if I get a flat ?? It would be short term till I could get the flat fixed. My service rep at the Hummer dealership said it wouldnt be a problem as long as I kept the speeds down and got the flat fixed ASAP.. Getting ready for our yearly fishing trip and trying to decide if I need to spring for a new 35 for my spare. Really dont want to spend the 200$ for a spare, but messing up my drive train fer sure isnt a option. So any helpful input would be nice. Thanks..

[evldave]

Originally Posted by StarsnBars

Morin all, Great spring day here in the midwest. I upgraded my tires to 35's except for the spare. Its a 33. Question,,, Will a smaller tire hurt my driveline if I get a flat ?? It would be short term till I could get the flat fixed. My service rep at the Hummer dealership said it wouldnt be a problem as long as I kept the speeds down and got the flat fixed ASAP.. Getting ready for our yearly fishing trip and trying to decide if I need to spring for a new 35 for my spare. Really dont want to spend the 200$ for a spare, but messing up my drive train fer sure isnt a option. So any helpful input would be nice. Thanks..

I've heard different things from different people on this subject. I used to have an XJ w/33" and used the stock 28" spare a couple times. I always used the spare in the rear (because your steering goes wacko w/two different sized tires on the front). And NEVER use the locker - you'll either get non-stop tire chirp or worse mangle your rear dif. I don't know what the FT 4WD will do w/a different tire, but I can't imagine in an emergency situation it would kill you.

Why not also carry around a simple tire fix kit. They are $5 at wallyworld and if you have an air compressor you can fix most flats on the trail in no time at all.

[fourfourto]

[
Why not also carry around a simple tire fix kit. They are $5 at wallyworld and if you have an air compressor you can fix most flats on the trail in no time at all.[/quote]

Thats what I do I dont want to lug around that spare.

maybe lower psi in the 35's and increase psi in the 33 spare if being used for a short time.
I dont think I would use the 33 with the 35's not worth the risk.
Also the 35 will look good hanging off the back.

[f5fstop]

Just make sure it goes on the front, and if in the back, DO NOT lock the locker (if you have one). Get the flat repaired ASAP, and don't drive too long on a highway or at high speed, and there should be no problems.

[StarsnBars]

Thanks for the replys. I think Im just going to spring for a cheap 35 I found,,, Dont want to hurt my ride. Again,, Thanks

[Casey]

Bringing this back up. Won't different size tires cause problems with the TCS trying to kick in? I remember a recent thread that when the wheel speed sensor was lost, the TCS kicked in and I think fixes were discussed to prevent false triggering on that event. I can see where this could cause similar problems.

In any all-wheel-drive vehicle, you really want all wheels sized the same.

Anyone here try running an odd sized spare that can comment?

[blindzebra]

Originally Posted by Casey

Bringing this back up. Won't different size tires cause problems with the TCS trying to kick in? I remember a recent thread that when the wheel speed sensor was lost, the TCS kicked in and I think fixes were discussed to prevent false triggering on that event. I can see where this could cause similar problems.

In any all-wheel-drive vehicle, you really want all wheels sized the same.

Anyone here try running an odd sized spare that can comment?

All wheel drive?

[Casey]

Correct me if I am wrong but in order to support 4hi (non-locked) operation there is a center differential in the transfer case which I believe is a limited slip torque biasing type. My definition of all wheel drive is one which has a center diff which allows on-road manuverability (such as subaru, mitsubishi, etc) and 4 wheel drive is one which has a locked center which provides 50/50 torque split and identical speeds to front and rear driveshafts (95% of 4wd applications on the market). In 4hi-lock operation is basically e-lock for the center differential.

I know in the eagle talon I own, the center differential is a viscous coupler which allows 50/50 torque split and differential speeds on the front and rear output shafts. However if front to rear differential speed to too high over an extended period of time, the fliud in the coupler will overheat and ruin the diff. The same is true for a clutch type limited slip differential. If you were to run different size rear tires, the clutch packs would always be slipping and burn up in short order.

Now I believe the H3 has true open front and rear diffs, and a torque biasing center type. Open diffs would not be a problem but its the center I would worry about.