AWD car needs a new tire; Replace one or all 4
 

On Jan 10, 8:51*am, phaeton > wrote:
> Went to Firestone today because I have a slow leak in one of my tires.
> The car is a 2002 Subaru Impreza TS with factory spec tires 195/60/R15.
> * Turns out the slow leak was due to a puncture in the sidewall of the
> tire, so that tire is garbage. *The tires are all about a year old and
> have decent meat on them, but the tech said you can't just replace one
> tire on an AWD car, you have to replace all 4 as a set, because the new
> one will be some sixteenths of an inch larger than all the rest.
>
> Of course he'd say that :D
>
> Now, I understand the concept and theory of this- *if all wheels are the
> same circumference, they all rotate the same amount and internal
> drivetrain components (center diff or viscous clutch) don't have to take
> up the slack. *But... I have a hard time believing that an amount
> measured in sixteenths of an inch is significant. *Surely a few pounds
> of pressure off, or an unbalanced load (i.e., some fatass sitting in a
> seat opposite some 80 pound child) would make just as much difference?
>
> I declined to make any purchase at this time. *I know I'll need to
> replace that one tire, but I have another vehicle to drive for now. *I
> would like to replace the one tire only. *Replacing all 4 is a bit
> unnecessary, right?
>
> Thanks
>
> -J

I immediately thought of a guy here who run mismatched tires on front
and back axles of
a quattro audi (torsen based one, not haldex crap based one
obviously).

the drivetrain was making all sorts of noise to a point that snake oil
salesmen offered to ditch the driveshaft essentially converting the
car to fwd.

all the noise was gone once the guy had installed 4 matching tires
audi requires.

the drivetrain on subaru would've been probably ruined by the same
treatment
but torsen seem to take this kind of abuse better, or so i would like
to believe