I've mixed and matched tires, especially in long enduros when maximum grip and performance wasn't the key factor to win a long race.
I also did it at the last minute before a ITB sprint race where I had made a lot of suspension modifications including stiffer shocks, sway bars and springs. Car was understeering really bad which I couldn't fix before the race. I stuck Goodyear GSCS (Hoosier grip) on the fronts and Toyo RA1s in the rear so I never did get a chance to test. I expected the Goodyears to grip much better than the Toyos but what I didn't consider was the time differential it takes the 2 tires to warm up and get to maximum grip. In turn 3, which is an off camber corner of the race when we were just getting up to speed at Thunderhill raceway , the rear end came around and I nearly spun out. I kept my foot in it and just barely managed to keep the car on the track and not lose any positions. Car got really wide in the corner and I think nobody wanted to pass a car on the verge of spinning!
By the end of the 1st lap, Toyos came up to temp and the car handled beautifully. I worked my way to 4th position and my lap times were within .1/sec/lap of the best laps of the top 3 finishers.
So yes, it can be done but be careful.
Joe Craven
71 ITB Capri
72 ITA Capri
77 GTI Cup
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