The lower rear tire pressure may increase footprint and ultimate traction, but should increase the slip angle of the rear suspension, making the car handle more neutral.

Slip angle is the angle the wheel actually travels vs. the angle of the wheel. Using front tires for a simple example, if you have the wheel turned 45D, the path over the road will be slightly less (let's assume 43 Degrees). Move this to the rear axle, when cornering loads are applied, the wheel will travel over the road at an angle off the linear axis of the tire. Increase this angle, and the car will "oversteer" without losing it's static coefficient of friction (skidding).

I don't think the guy is skidding around the corners (i.e. fishtail or 4-wheel drift) but the slip angles influence the cornering characteristics of the vehicle.

I recall reading all about this in someone's book on high performance driving. A fun test for you kids at home - drop your rear tire pressure to 15 psi, go out on the highway, and see how squirrelly the arse end is (oversteering) to get an idea. (Closed highway. Professional driver.)

I may be completely wrong here, but that would be my thinking.

Keep off the cones and hit your apex,

Ludwig


posted by 207.124.16...

• Autocross 99 suspension >>, BobD, Thu, 27 Mar 2003 00:04:56
  • Re: Autocross 99 suspension >>, GM, Fri, 28 Mar 2003 22:14:37
  • Re: Autocross 99 suspension >>, james, Thu, 27 Mar 2003 20:09:49
    • rear axel question, GM, Sun, 30 Mar 2003 15:14:55
    • to cut brake signal from apc, gorper, Thu, 27 Mar 2003 20:28:37
  • Re: Autocross 99 suspension >>, Eric Law, Thu, 27 Mar 2003 08:05:37
  • Re: Autocross 99 suspension >>, gorper, Thu, 27 Mar 2003 00:31:48
    • Re: w/~4 lb psi lower in rear, officeboy, Thu, 27 Mar 2003 11:58:53
      • f/r pressure differences, gorper, Thu, 27 Mar 2003 17:03:02
      • Increased slip angle, chris, Thu, 27 Mar 2003 13:10:46 <-- Viewing This Message
        • Actually, I've found higher rear pressure was better, CFishgo, Thu, 27 Mar 2003 19:51:04
          • Yup..., Andy E, Fri, 28 Mar 2003 04:59:07
        • Re: Increased slip angle, lms, Thu, 27 Mar 2003 14:33:30

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