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Pobst Position: Suspension, Hard or Soft?
Page: 1 Links
Pobst Position: Suspension
There's more than one way to skin a lap time, friends, but I know what I like. I'll end the suspense right up front. Compliance. Is it any wonder? I grew up Soloing my street cars, then racing warmed-over sedans for years. My girlfriend Debbie's 1975 Rabbit taught me that bodyroll does not necessarily mean slow. I'm guessing now that an important part of the reason that Rabbit worked so leaned over was the skinny high-profile tires it ran. I could go to the used-tire rack at any grimy old tire store and if I found any european brand, I knew it would be competitive. I still vividly recall being thrown out because my Datsun Roadster did not have the original equipment air injection pump when I was running 175/14 Gillette Golden Bear Specials, from Montgomery Ward, I'm pretty sure. Definitely a cheater looking to win at any cost. Didn't have half the original paint, chrome trim on one door and two fenders, nor more than half the oil in the original shocks any more either. Uh, oh, A.D.D. Randy goes off on a tangent again.

I have always felt that tires have more traction if they are actually touching the ground. We're racing the KPAX/3R Porsche at Sebring as I write this, and I'm in a good mood because I'm likin' the way my car is feelin' on today's test day. Compliant. Many of the racing Porsches I have driven over the last ten years have been quite aggressively sprung and shocked. Brutal, even, sometimes. The closer to Stuttgart, the stiffer. The stiffer your suspension, the more your tires flex. Flexing sidewalls build heat. Heat is the enemy of the tire. What is the upside of stiff? Quick weight transfer for one, no waiting for the suspension to move and settle. Less change in geometry as the suspension moves, as well. A stable aerodynamic platform, for another. If your car has wings, or ground effects, like tunnels, a flat bottom, of even skirts, the suspension may have to be stiff to preserve the proper clearance and angles of those devices. Be sure to pad your seat. By the way, I love the outrageous aerodynamic devices appearing on more and more Solo cars, especially the Modifieds, perhaps the last bastion of creativity in motorsports. Take that, Car of Tomorrow, ha.

I have heard it said and experienced myself that race cars from Europe are often sprung more firmly than in America. One theory is that the tracks are smoother over there. In general this is true, but they still have curbs and bumps anyway, just not on the level of a Sebring or Lime Rock. My thought is that so many racers in Europe start in karts that they get used to the feel of no suspension at all. When the suspension is unrelenting, the tires break loose and regain traction as the tireloads fluctuate due to impacts from the road surface. The driver must constantly correct with the steering, flicking the wheel. Not my preferred style. I like cars that are driven with calm hands. Hooked up. Of course there is a limit. There should be no wallow, no bottoming, and bodyroll should be controlled with a good set of anti-roll bars.

What I like about compliance is that it usually promotes predictabilty, and this is a critical factor in going fast. One must be able to trust the car. Softer suspensions usually have a more gradual breakaway at the limit, enabling the driver to stay right on the limit without going over and testing his car-control ability. Another way to do this is to be sure you have at least a little understeer in your setup. Understeer is easy, and becomes merely frustrating when over-evident. Oversteer is what scares you. Got sweaty palms, or that nervous tension in your belly? Are you regularly puckering your pooper muscles in the fast corners? Soften it up, and add understeer. You will be amazed how easy and fun it can be to drive your formerly tempermental, beastly race car. And guess what? You'll be much faster, too.
Originally printed in Sportscar May 2008
 
 
 
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