>>>subaru 4 tire replacement scam
What dogmush said. If there's a significant difference in revolutions between the 4 axles, the powertain management unit lights up the dashboard like a Christmas tree.
My personal experience had a tire shop put 3 blizzak ws90s and 1 blizzak ws80 (all 4 the same size) on my WRX as we headed out of town on a 7000 mile cross country drive. A few months after the trip it was no longer winter and time to reinstall the summer Dunlops.
I realized at that time one blizzak was different, checked the differences in specifications between the 80 and 90, and scoured the Subaru factory repair manual for reference or confirmation of this legendary "4 tires or carnage" myth. It did not appear therein.
I made the call to the tire shop and took the wheel with the odd tire and the bill of sale and left with one brand stinkin new ws90.
The 0 mile tire, when installed with 3 - 10,000 mile snow tires (arguably 25-30% worn) ran flawlessly, and resulted in none of the promised metallic chunkage.
The dashboard lights had no comment.
Single data point.