Date: Wed, 08 Nov 2000 22:54:53 GMT From: Bob <uctraingnopsamanet.com> Subject: Re: Doubts about the 9-3's "nervousness"
On Wed, 08 Nov 2000 03:31:49 GMT, "Brian Greene" <Delinquent1nopsamdnet.att.net> wrote: Brian: I agree with your conclusion but I think you have a little misunderstanding about wheels & tires. >I have to agree with Steve on this issue. The most appealing aspect of a >17" wheel is not comfort, it is not additional weight... Additional unsprung (wheel) weight is *always* a negative. No car ever needs additional unsprung weight and it will never help handling. It sounds as if you're suggesting that a heavier wheel might actually be of some benefit. >it is the fact that >the bigger the wheel, the more rubber touches the asphalt. Given a vehicle of the same weight, the same area of rubber touches the road with a wide or narrow tire of any wheel size. However, a 17" wheel implies a low profile (40 to 45 series) tire and the reduced sidewall height allows more tire to stay in contact with the pavement in severe cornering. When properly sized, a 17" tire has the same diameter as a 15" tire on the same car - it just has a shorter sidewall. > The more rubber on the asphalt means >less torque drive (torque drive definition: speed wobbles when you stomp Wider wheels/tires generally _increase_ torque steer or "tramlining". This is due to the fact that to fit the wider tires, you have to reduce the offset of the wheel - the extra wheel/tire has to go somewhere, and there's no room on the "inside" of the wheel. When you reduce the offset you increase the track width and increase the aforementioned problems with it. >gas). Low profile tires are not only utilized because of the rigidity of >the sidewall but because there's not a whole lot of room in the Saab wheel >well. If you change the size of the wheel then you adjust the size of the tire as well - at least if you're doing it properly. The goal is to have a larger wheel with a shorter sidewall but a tire of exactly the same diameter. However, as you are making the tire wider, you also run into clearance problems. So, larger low profile tires, which are also wider, DO NOT HELP AT ALL with the "size limitation" of a wheel well. FYI, Bob
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