RA-1's do take a longer time to warm up...they help for AutoX compared to most street tires, but don't ever heat up enough to get their max grip. I had run RA-1's last year for AutoX...I just switched to Hankook's autoX tire and the difference is night and day! Just look at the difference in the amount of rocks the 2 tires pick up...the Hankook's are on top, the RA-1's on the bottom (I had brushed off both tires, but the rocks in the Hankook's were stuck!):




-Peter