They run 'softer compound tires' than series like FIA GT, WTCC, V8 Supercars, the WEC GTE class etc. The normal pace for those cars (GT500) is a bit faster than lmp2's. Take Fuji for example, lmp2's pace is around 1:32s for pole. GT500 was 1:31s for Kazuki Nakajima in the SC430. GTE class pole in the WEC was around high 1:38s while GT300 pole was 1:37's this year for the BRZ GT300. People complain about the soft tires in GT5 saying they're 'arcadey' blah blah. My theory is you run the closest type of tire the series uses. Super GT cars have high grip tires. So Mediums or Softs I think represents close to what they use. Mediums last a bit longer, but not as fast. Series like FIA GT3 will probably run a hard tire that has great life to it. LMP's are both. They have tremendous grip and long life (triple stints at LeMans).