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Old 12-04-2009, 08:48 AM   #1
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In this area, racing tells us Nothing about our "ideal" tire selection. That can only be determined buy comprehensive testing.

For F1 it's easy, build tires to match the maximum allowed height and width, to fit the maximum allowed wheel diameter. Whatever profile that works out to is purely coincidental.

Using your max. diameter and width numbers, the profile would be between a 46 and 54 "series", depending on tire width. Racing tires usually just use a diameter X width designation, such as 26"X13"-13.

Last edited by stephen wilson; 12-04-2009 at 09:01 AM.
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Old 12-04-2009, 08:50 AM   #2
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Yeah, I didn't think about that issue, my 18's do "tram-line", but I find it acceptable.
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Old 12-04-2009, 09:06 AM   #3
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blue2000s - I may be in the minority, but I'm really happy with my 17s. There's more than enough grip for the roads, the ride is stiff but not painful with the M030, the risk of bending a wheel on a pothole is relatively small, and tires are cheaper. I prefer a little narrower tire for minimizing tram-lining and somewhat increased feedback.

I'm not entirely happy with the style of the stock 2000S wheels, but I actually don't think 18s+ enhance the car's looks given the same wheel style, but that's subjective, of course.


I am going to have to agree with you on this one. I like the 17s for function and asthetics. Tires are cheaper, that is for sure. I just got a new set of wheels for the summer, and again, I went with 17s (though in the BoxS II design).

I love that everyone has their own opinion though. I enjoy seeing what other owners put on their cars in the pics.
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Old 12-04-2009, 09:21 AM   #4
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Wheel size is a compromise. You are balancing cost, weight, aesthetics and responsiveness to direction change.

Basically:

Cost: 17 is cheapest cost, 19 highest - 17 wins

Weight: 17 is lightest, 19 is heaviest - 17 wins

Aesthetics: 19 is prettiest 17 ugliest - 19 wins

Responsiveness: This really has to do with tire aspect ratios not wheel size. For the same overall tire height the 19 will be most responsive and the 17 least. However the 17 will have less unsprung weight which also contributes to responsive handling. Call this one a wash.

The 18" is probably the best compromise.

If you ignore aesthetics then 17" are best. They are lighter. The key is to not use the stock tire aspect ratios with the 17" wheels but instead use the same aspect as the OEM 18" tire. This will give the same responsiveness as the 18" and will lower the car by about 1/2". The combination of reduced unsprung weight and lower CG will result in a noticeable improvement in handling. The reduced unsprung weight will result in better acceleration and braking performance as well as a slightly smoother ride. The lower rolling diameter will result in improved acceleration at the expense of higher cruising RPM, poorer fuel economy and an inaccurate speedo.

The problem with the factory 17" wheels is that the are also narrower than the 18" or 19" so you can't mount as wide a tire.
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Old 12-04-2009, 10:01 AM   #5
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renzop, I agree completely.

To elaborate: I think the aspect ratio is actually a poor specification to use for comparison, as you mentioned, the true indicator is a tire's section height. I believe a section height close to 4" is a great high performance street car compromise.

OEM 17" section heights are around 4.4" front/ 4.6" rear, 18's = 3.7"/4.2" , and 19's = 3.2"/3.7"

Steve
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