Just bought Jeremy Clarksons No Limits and it pretty good.
There was the bit with the 172 (in red, looked very very nice) they had Jonathan Palmer driving round a track with 3 different sets of tyres. The standard one, some remoulds and some performance tyres.
The performance tyres were a second quicker than the standard and the remoulds were slower. I think the peformance tyres were Yokohama AVS Sport.
Just goes to show what difference a tyre can make!