18” race rubber by Continental, Bridgestone and Metzeler is readily available, cheap and sticky. Marvic can make you a set of magnesium wheels in 18” for around $2400. Weight for both is less than the weight of 1 OEM.
17” tires are readily available but now you have a wheel problem.
go to 18s and you have no problems.
speaking from experience here, not BS. I run 18” Continentals 130 rear and beat guys on 150/160 wide 17s all the time.