First of all, thanks very much to Alice.thomas222, mud, and ratta tat tat for replying, and also for your nice comments regarding my car.
To mud and ratta tat tat, the reason for using this tyres have a mix of what you are saying. First, according to regulations we have to use street tires, Second, G1 cars are not that powerful, so in circuit races, besides of using street tires, we use a smaller size, (165/70/13 and 3.89 C&P), to have a smaller final ratio. when we are in rallyes, we use either one combos, beeing the other 175/70/13 tyres and 3.54 C&P, and if the rallye is very twisty, well, another combinations of tyres and C&P can be made. In all cases we have LSD.
In this pic we have 165/70/13 with 3.89
Cheers,
Eduardo