18" and 19" Comparison
Had an hour at PDE Silverstone last week, with 2 cars to try back to back. Both had PASM and Sport Chrono, one had 19" Carrera S and the other had 18" Cayman S.
Started on the 18" and spend nearly 30 minutes building up to a reasonable pace on the normal setting. I have driven faster on this track but I wanted to hold back for a bit so that I was smoother and therefore consistent for the comparison. Then the car was put into the sport setting and after a few laps to adjust, I was lapping just as quickly. The body control under weight transfer was much better but the car was deflected slightly more by bumps in the track. No real surprises there and needless to say, the car was fantastic.
Then I jumped in to into the car with 19" on the normal PASM setting. The immediate impression, even at slow speeds, was how the car was more susceptable being deflected by bumps and camber changes than the 18" with the PASM on firm. Turn in was more zealous but but the steering did not seem to have the same linearity. This may have been my mind playing tricks on me but it felt like turn in was being impeded by the added inertia of the bigger wheels, yet at the same time enhanced by the tyre's agility from the lower side wall. It didn't feel balanced. Putting PASM into sport mode helped a little but the car was then even more prone to following the vagaries of the surface.
The upshot was that I found the 19" car much harder to drive smoothly and keep on a consistent line. Of course, this meant I was slower, which was noticable even to a spectator (the instructor picked up on it immediately).
This was all being undertaken to finalise my specification and for me, the 18" are the way to go. On the road (my car will be a daily driver) they are quiter, much more comfortable and apparently wear better (not a massive consideration). Then for the track, they seem to suit my driving style and they'll certainly help me improve, which is a big consideration.
