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.
> =A0 Turns out the slow leak was due to a puncture in the sidewall of the
> tire, so that tire is garbage. =A0The 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
>
because that's what FHI requires.
Now, I understand the concept and theory of this- =A0if all wheels are th= e
> 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. =A0But... I have a hard time believing that an amount
> measured in sixteenths of an inch is significant. =A0Surely a few pounds
> of pressure off, or an unbalanced load (i.e., some f***ss sitting in a
> seat opposite some 80 pound child) would make just as much difference? >
> I declined to make any purchase at this time. =A0I know I'll need to
> replace that one tire, but I have another vehicle to drive for now. =A0I
> would like to replace the one tire only. =A0Replacing all 4 is a bit
> unnecessary, right?
That's what you'd like to believe. But it is does not make it right. If it makes you feel better I see subarus and quattro outfitted audis run on single axle brake force testing contraptions right and left. (during annual technical "inspections" for example)
I never saw a gadget for testing brakes in a US of A auto shop, not the one that spins two tires at the time (ruining awd hardware on subarus).
I specifically do not buy a used subaru because of the cheapskates like you: one never knows what thew center diff was subjected to.