Sticker on my 1991 745 T says 195/60R15. I use Yokohama Avid H4S. Good price, great grip (not that I throw the car around that much, but good to know that it is there when you need it), and the typically GREAT Yokohama wear/mileage. If not abused, expect 60,000 miles or better. UTQG is 500 AA A, yes, AA traction rating. And, in my experience, Yokos don't leak much, if at all. They almost never need air.
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Scott Cook - 1991 745T, 1985 RX-7 GSL-SE, 1986 Toyota Tercel (Don't laugh, it is reliable, faithful AND gets 41 mpg!)