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[jimbo]

Are there any automotive engineers out there who can indicate or point me toward determining optimal tire sizes for a given car?

The Solstice will be equipped with P245s on each corner. I just read a post by slowandlow stating he might go to 255s on the rear for more grip and I wonder if it would even be of any benefit.

How did the Solstice engineers determine the optimal width of tire for the car? I don't know how to determine that quantitatively. For all I know it is a complicated balancing act. You want to optimize sports car performance and maximize launch from a standing stop, maximize grip on the skidpad and mimimize braking distance. For all I know, one tire width may not satisfy all 3 conditions.

But wider is not always better. Wider tires have several disadvantages and rolling resistance is the primary enemy. Not only do they increase unsprung weigth, they have less grip on wet pavement, have more inertia to overcome accelerating and at steady state speeds, hurt fuel economy, and possibly increase wheelspin upon launch from a standing start due to less pressure on the rubber surface due to the same weight acting over a greater contact area.

How do they determine optimum tire widths for race cars? Is there a forumula or something accounting for weight, wheelbase, front and rear weight distribution, track, and wheel diameter that they use to determine the best width for racing tires? Not everybody races with 700 HP machines. And I'm sure your SCCA Miatas don't wear the same width rubber as Nascar machines.

So how do race teams determine the best width of tire and how did the GM engineers determine to go with P245s for the Solstice? I'm chomping at the bit to know.