Quote:
GR said:
A smaller tyre sidewall will decrease the tyre's slip angle during cornering, i.e. the amount it can twist away from the rim to go straight on rather than where you want . On the fronts, this leads to earlier understeer but it is countered by earlier oversteer at the back. But despite the earlier onset of a slide with a large sidewall, the trasnsition from grip to slip is longer and smoother. In a nutsshell, the larger wheels grip more but let go more suddenly, which is generally deemed unpleasant.

Then there is the increased weight of the larger wheels, which any engineer will tell you is not good. The less unsprung mass (wheels tyres, brakes etc.) the better the turn in.

The differences were quite noticable when I tried the 17" and 18" wheels back to back when speccing my 986. Also on that car, the larger diameter tyres were proportionally wider at the back, which increased understeer but I am not sure on the differences between the new 18" and 19" wheels/tyres.

And as you say, ride is compromised with the biger wheels but also, tramlining increases (when the car follows the camber on the road, rather than where you're pointing it).

All the Porsche driving instructors I have met in the UK preferred the 17" wheels on the 986 and 996 C2 and C4 but I have not spoken to any regarding the 987 and 997. My guess would be that they prefer the 18" on the new cars

So your choice depends on how hard you want to push your car and how controllable you like it right on the limit, compared to how it looks and rides. Personally the smaller wheels win for me.



Thanks GR, It's got to be the 18's then for me, but the 19's in the promo. shots look so good.