ok, so i need two new front tires, theyre toyo proxes 4 235/35/19, i have 2 on the back already with 70% tread left on them. If i just bought 2 new ones for the front (the fronts wear fast anyway due to weight distribution). I should be fine right? (with the quattro system). thanks
do a search, I believe you are out of the acceptable range in the difference in tire depth for the quat system. I THINK it is something like no more than 1/4in in depth difference between any of the tires. Have you been rotating your tires? The quat system is very robust, so you have that in your favor.
With quattro each tire has to be within 3% of each other. In your size the tire diameter is 25.5 inches. 3% of that number is .765. If you divide that number in half, to account for both sides of the tire, you are left with .385. When measured in inches this is 12/32. Since typical tire tread is 10/32 or 11/32, with a 12/32 tolerance, you are theoretically always within tolerance when you change a tire. With that said, I would only keep the old tires if they had at least 6/32 of tread.
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treadwear question - 
