13" versus 15" wheels

[Smithy77]

F1 remain with13" as a legacy, that is the point. They are designed with little and poor suspension characteristics and make use of the tyre to provide suspension. They are engineered around the tyre because of the tyre. They would need a radical change to make use of a different configuration which would give them packaging issues etc and certainly rebate the grid

if they were so great why would not see all race cars set up so, lemans, WTC, etc etc etc.

Mavic, fair point. However, tin top racing (Lemans, WTC, BTCC etc) are evolutions of road cars, therefore there is an emphasis to stay in-keeping with road cars (as opposed to a specific performance advantages, one could argue). 

I think most (if not all??) purpose built race cars, i.e. single seaters, use the more traditional small wheel/high profile set up, from F1 down to Formula Fords (OK, FFs might not be quite as extreme as the high profile of F1 tyres, but they a far from the rubber bands used in tin tops)

But the point about having to design and enginer all other aspects of the chassis to get the most out of what ever tyre/wheel combination the car has is the pertinent point here - you could probably get small wheels/big tyres to handle just as well as big wheels/small tyres by designing/setting up the chassis accordingly. So I guess the optimum choice comes down to a combination of preference of 'feel' you want to get from the road, and what the basic Caterham chassis is best suited for - can anyone catergorically confirm the latter point?

[AntonyH]

why have F1 cars used 13s with huge profile tyres for years?

Because that's what the rules say must be used?

http://www.autosport.com/news/report.php/id/114907