It's because Michelin developed the tyres to suit the LMP1 class as it was a couple of years ago, and the best way to make Porsche, Audi and Toyota happy was design them to work best with the 4WD cars. They didn't bother making a set specifically for ByKolles because...it's ByKolles.
It's not that the teams are required to run those tyres, it's more that that's all that's available for them to run.
|