awd question

[Underground_Killah]

i was told that on awd cars (all wheel drive) that when you have to replace one tire (blown out, flat, etc) you must replace all four. is this true? and why?

[psychorallyfreak]

Uh.....no. It wasn't the guy at the tire shop, was it?

[Moppie]

Its import to maintain the same rolling diameter across an axle so that the differential in the middle is not over stressed and subjected to excessive wear.

In a 2WD car this means the two drive wheels have to be the same size, and the two non driven wheels can be of a differnt size.
However an AWD has an extra differential between the two axle sets and on many AWD cars having just one tyre that is a differnt size can place extra strain on it, as the front tries wheels turn at a differnt speed to the back wheels.

[Underground_Killah]

nah, i don't believe a word any one at the tire shop says (even my cousin who's the manager) i was just told at the subaru dealership about it today when i was with my girl looking at cars

[psychorallyfreak]

Well, if Mr. Killah here is even that stupid (and he better not be!....ha ha just kidding) as to put tires on his car that differ THAT MUCH as to put undue stress and strain on his car, then he shouldn't be driving.


(EDIT: can't friggin' type!)

[Moppie]

Originally Posted by psychorallyfreak

(EDIT: can't friggin' type!)

Not a bad thing,since you don't have some real technical knowledge to share it might be best if you didn't type anything.




Take a brand new tyre, and a badly worn tyre, measure the differnces in rolling diameter. It won't seem like a lot, but now work out the differnt speed each tyre will be rotating at say 100kph. Its easily enough that if you drive only a few hundred kms (say to and from work for a week) you can do serious damage to a differential.

[psychorallyfreak]

How badly worn?
Plus...what kind of differential are you using?

And, I did not enjoy that "no real technical knowledge" stab. I didn't insult you, so I would like it if you didn't insult me.
Personally, I've been working on cars since I was about 12. I've developed my "technical knowledge" in the real world, not yet in a classroom (but it's in my five-year plan).

I don't want to argue, and I'm sure what I said above doesn't help the situation, but I wanted to get that out there.

To finish my wanderings off, I just want to say that in my experience of working on shitty cars where the tires aren't the same rolling diameter between the four tires, none of them have had a worn out differential because of it.


Thanks for your time...

[Ground Rat]

You won't hurt anything if you just replace that one tire.