Quote:
Originally Posted by Taxi645
However, the change was opposed by Pirelli both for reasons of practicality and because of the potential marketing impact. I'm quite sure that they didn't switch from 13'' to 18" for practicality reasons so that leaves marketing as the only reason to go to 18''. Just as I have said before in this thread.
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Most racing categories use 18" tyres, so that does make sense.
What puzzles me is,
if lighter smaller diameter wheels with higher profile tyres are faster, when given a free choice (the only rule being overall maximum diameter) why did ALL the Super Touring teams immediately go to the largest possible 19" wheels?
So that suggests wheel weight is not that important? After all, many F1 teams were using 15" wheels with relatively low profile tyres, before 13" wheels were made mandatory and eventually Bridgestone decided to make front tyres the same diameter as the rear (now the case from 1997 to the present day).
For example, here you can see the low profile 13" fronts and relatively lower profile 15" rears on the older Grand Prix car, in stark contrast to the very high profile 13" tyres front & rear mandated for the 1990's Grand Prix car:
If lower profile tyres on 15" rears were slower than high profile tyres on 13" rears and lower profile front tyres were slower than high profile ones, why would March specify them?! The profile of the fronts is also not far from current F1 cars either (obviously the profile will be reduced more in 2026).
The Super Touring and F1 examples tend to suggest that, overall on balance of unsprung rotational mass, tyre weight, sidewall deflection, kinematics, tyre contribution to wheel rate (undamped, uncontrolled wheel rate which is bad), the low profile tyres & heavier wheels are
not slower (at least not for a circuit car, unlike a drag racing car where there is huge deflection of the rear tyre).
For pure inertia-dominated straight line acceleration the smaller wheels + high profile tyres are faster, and for wet conditions the high profile tyres that deflect more are faster
BUT overall for a circuit racing lap in the dry, it seems the way the stiff short sidewalls better manages cornering forces may actually be faster despite the greater rotational inertia (testing by the likes of Tyre Reviews' Jonathon Benson backs this up for road cars, 17" fastest in the wet, 19" fastest in the dry).
Quote:
Originally Posted by Taxi645
Marketing over the core interests of the sport itself.
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I don't think it is clear cut that 18" low profile tyres are slower than 16" or 13" higher profiles on a
dry circuit,
even with the extra 25kg of rotational mass.
Why can it not be performance as well as marketing?
