Originally Posted by Skiddins

It depends on the track and how bumpy it is etc.

I have been running progressives all round on asphalt and found it can make the car more consistent. Then at another asphalt track that was faster and smoother I ran 2.9's with 2.7's

2.7 and 2.5 work well on carpet. If grip comes up enough you could run 2.7 front and rear.