I'm assuming these are G-Force R1s and not the previous incarnation of the R1s (no G Force printed on the sidewall). The prior R1s reacted completely opposite to all other R tires, because of their stiff sidewall - lowering the pressure tended to reduce sliding on that end - typical hot pressures for the old R1s were 23/25. The latest G Force (from last year) reacts like most other R tires - higher pressures than optimal tend to reduce sliding at that end - typical pressures for G Force tires are 27/30. Optimal tire pressures are car dependent on weight, suspension and alignment. Using a pyrometer correctly is best, but you can gain some idea by altering pressures at an autocross and track and noting the differences - you may find that lowering pressures induces a slightly mushy feel but drops lap times, or that raising pressures increases responsiveness, but that the car wants to slide more quickly. There are no hard and fast rules regarding tire pressure.
Randy W
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