17" Sidwall Stiffness

[edevlin]

Well I just got my worn-out Pirelli's replaced with 4 new Michellin's. The Michellin's give a noticably smoother ride on my Boxster. While I was waiting for the tires to be put on at the dealer, I got to test drive a 2006 Boxster S with 19" wheels, wow.

I was amazed at the smooth ride and the very quick handling of the new car with 19" wheels compared to my 2000 2.7L with 17" wheels. When I would turn the steering wheel in the 2006 Boxster S, it would go there - right now. In comparison, my car felt sluggish and soft when I would do the same amount of turning. I was wondering how much of the "sluggish" stearing in my car is due to flex in the sidwalls of my 17" tires and how much is differences in suspension.

I was also impressed that the ride was smoother even in "sport" mode in the new Boxster S. I thought the 19" tires would give a rougher ride. Any thoughts?

Ed

2000 Boxster
48K, stock suspension
17" stock wheels,

well most people in this forum think that 19 inch rims are not a good choice for a boxster. i for one love the way my car handles with 19z. i've read so much here that 19z were not the way to go. well i never listened and put the 19z on anyways. the car feels exactly the same as when i had 17z. i feel no difference, other then i have to be carefull not to bend a rim. the 19z are just more accecptable to bending/denting.

actually the car feels very stable with the bigger 19z.

i'd even put 20z, but the porsche race shop guys would of killed me.

[SD987]

There's some significant chassis/suspension changes between the two models but I'm thinking the difference you noticed was the variable steering ratio on the 9X7s which use hydraulically-assisted rack-and-pinion steering.

The ratio around the center position, i.e. for small movements of the steering wheel, is similar to that of the 986. As a result, the vehicle remains very smooth at high speeds. But the steering ratio becomes increasingly more direct with steering wheel movements of more than 30° to 240° (approx. 1/8 to 3/4 steering wheel revolution). This is achieved through a gear rack with variable tooth pitch.

The steering wheel revolutions from stop to stop were also reduced from 2.98 on the 986 to 2.62 on the 987 which greatly improves agility.

As far as the 19s verse the 17s, I had 17s on my 987 base and 19s on my 987S (which also has PASM) and the handling feels pretty much the same. If anything, I'd actually say the 987 base feels more tossable than the S although I think there are other factors that give this impression in addition to the tires. However, I think the 987S would run a faster slalom time, although it might not feel like you were going as fast. I don't feel the 19s with Sport mode is too harsh, although I'm one of those who think the 987 is best suited for 18s, which would lead me to believe that 19s aren't the best fit for the 986 (although I obviously don't have an owners perspective there).