awd tire replacement

[laz_10]

i dont own a AWD....yet, but i overheard a mechanic over at sears automotive center telling a customer who owns a AWD car, that she would have to replace all 4 tires even though just one needed replaced. he told her that if she replaced just one tire, it wouldnt be good for the LSD, because it would throw it off or something like that. that one tire "in theory would either be going faster or slower than the other tires, which wouldnt be good for ur car", now is this B.S or is there truth to this?

[vvtlikick]

Differently sized tires can ruin a LSD. I remember the S2000 spare tire can only be used on the front for this reason. A flat in the rear requires you to move a front tire to the rear and use the spare up front.

I think the most wear will change the size of a tire is around 2% or 3%, but I don't if this is enough to cause damage.