As I posted in another thread on CSL prices, the Cup tyres do make a difference to lap times but not as big a difference as you seem to suggest.Nordschleife wrote:It is really easy to forget that the tyres make all the difference to lap times. The discussion here is about differences whichj are less than the differences which arise from changing to optimal 'road legal' track tyres. My friends with M3 CSLs have 3 sets of wheels - winter, spring & autumn, and summer. The summer tyres are lethal out of season and not even much good on wet roads. These are what the car is shipped with ex-factory. If you substitued these tyres for those which the Porsche Turbo and Lamborghini Gallardo have as standard, the relative ranking would change. This is especially true at the Ring as the M3 CSL is lacking in the top end on such a high speed circuit.
The factory default for a CSL was normal M3 19" wheels with normal tyres - you had to explicitly order the special CSl wheels and Cup tyres and also had to sign a disclaimer in order to have BMW provide them.
It's untrue to say that the Cups are lethal out of season or that they are'nt much good on wet roads. There are several M3 CSL owners here in the UK who run Cups year round - the particular conditions that Cup tyres don't like are temperatures lower than 7C or deep standing water when obviously their limited tread depth makes then very prone to aquaplane more than normal tyres. If you're aware of these two limitations then they're OK. With regard to your top end comment, I don't know whether the CSL that did the lap time at the Ring was derestricted but if it was then there is'nt much in it at top end speeds between it and the Porsche/Lamborghini.
As I commented on the other thread, the CSL even when shipped with CSL wheels and Cup tyres by BMW is'nt optimally set up (suspension wise) to get the best out of the tyres. Setting the suspension up to optimal Cup settings would undoubtedly see the 7.50 figure come down further.
