Tyres, another subject often debated.
I would guess that the W9533 (Ferrari 375) and W9206 (Sharknose are made of the same compound. The four tyres give a nice range of sizes, it's just a pity Scalextric will not supply them!
Once the wheels are done I will look into tyres. Urethane casting is fine, but not for large quantities, so enquiries are now being made regarding manufacture of tyres to a pattern.
All the available (occasionally) tyres are somewhat wide, with the Sharknose fronts at about a scale 7.5" and the 375 tyres about 7.35". By comparison, the tyres for the Maserati, (slightly larger I/D), are a scale 5.6", not too far out for a pre-war racing car.
Thus, an open question. Would it be worth getting tyres made similar (!) to the Scalextric fronts? The target price would be £4.00 per set.
I'll pop on a couple of pictures if so required.