My father had some really bad rear wandering when he had radial front tires and bias ply back tires. He made the switch for bias ply front and rear and says the car handles much better. His car runs 11.40's around 120 mph. I raced my grandfather's Demon with radial front and bias ply rears and it handles great. The Demon runs 12.50's around 110 mph. I think the faster the car the more it is effected by mismatched tires.