Through a series of calamities, I've ended up with a spare tire with a slightly smaller diameter than than other four - 205/70-15 vs 205/75-15.
I rarely need 4wd mode, but what (if any) complications can I expect if the smaller spare is used temporarily? The law of averages dictates the spare would likely be used on the rear axle in 2wd.
Oh, the truck is a '96 S15 Sonoma.
TIA!
From what I have read you should use the smaller spare on the non-drive axle. So if you get a flat on the rear you need to move a wheel from the front to the back and use the spare on the front.
In 2wd, temp. use should be ok. In 4wd, if you have open diffs and are in snow, you should be ok for a short time. If you have locking axles, get a correct spare.
It might be interesting to do the math on the differential use. I wonder how many miles of city driving, that requires sharp turns and differential use, would equal straightline driving with a mis-matched tire?
Unequal tire sizes put a lot of strain on the drive train when in 4wd.
If you want to see wind up, just put the truck in 4wd drive and make a sharp turn, stop and jack up one wheel.
Short answer: Dont do it. Long answer: Don't do it unless a "I am broke down on the corner of 5th and Kill Whitey and must get home NOW." situation arises.
just carry a can of SUV-size fix-a-flat and forget the wrong-sized spare.
93gsxturbo wrote: Don't do it unless a "I am broke down on the corner of 5th and Kill Whitey and must get home NOW." situation arises.
you're just saying that to get your quote in the magazine 
No big deal on that truck.
In 2wd, it doesn't do anything. Which ever axle it's on, it will make the pumpkin rotate slowly to compensate for the difference in rotation rate. Nothing different than the way the pumpkin rotates when you go around a turn and the wheels rotate differently.
In 4wd mode, it puts a bit of stress on the transfer case, as the driveshafts will be rotating at slightly different speeds. Just like they do when you go around turns. So the tires slip a little bit. This is just fine on dirt roads, wet pavement, snow, etc. It creates a little more stress on things when you do it on dry pavement.
You've already experienced all these stresses just driving on dry pavement in 4wd.
foxtrapper wrote: You've already experienced all these stresses just driving on dry pavement in 4wd.
Shouldn't be driving on dry pavement in 4WD.
Had a customer, 4cyl,4wd pickup, complained that his truck would lose power every time he put it in 4wd. I went out to look at the truck. Turns out he had two brand new tires on the rear and the fronts were almost bald. told hime to put two new tires on the front and his problem would go away. Took some explaining as to why.
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