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Originally Posted by John V
Jim, I'm not trying to be difficult, but it's really impossible to know just by looking at the suspension alignment settings how the car will behave. I'm sure the engineers did what all engineers do: they started with a baseline (based on past experience, computer modeling, etc) and then went out and did some testing. From there, I'm sure they tweaked spring rate, tire size, ride height, ARB thicknesses, damper valving, alignment, etc to acheive the balance of ride and handling (and within that, the balance of safety and tossability) they wanted. But no matter how smart you are and how much you know about suspensions, it's impossible to just look at all these pieces of hardware and tell ANYthing.
Someone always mentions the skidpad test. I think it's the most over-published figure of merit when talking about automotive performance. How often are you driving a Boxster around a perfectly flat piece of pavement in a 100' radius curve? Not very frequently. More often, if you're driving spiritedly, you're dancing the car through a series of switchbacks. Or you're driving on a country road with rolling hills and fast, sweeping corners. Either way, it's dynamic. You're on the throttle, on the brakes. The corner decreases or increases in radius.
Forget spirited driving for a moment and consider a complete non-enthusiast driving the car. In certain circumstances, the car's natural tendency is to understeer. In other circumstances, the car's natural tendency is to oversteer. In fact, in my opinion the car is set up to oversteer in a situation which your average driver could encounter - the typical USA freeway exit ramp - which is a decreasing-radius corner after a high-speed straightaway. Go into that corner too hot and drop the throttle and the back end will come out. Your average Honda, Toyota or even BMW won't do that. Of course I like this kind of behavior - it makes the car interesting to drive, and it gives the driver a bunch of options when it comes to driving quickly. But when it's raining outside and my girlfriend has borrowed the car? I'm not thinking about it being a steady-state understeerer, I'm thinking "what are the odds she's going to back it into a guardrail?" (Fortunately, she can drive).
I think this is an interesting discussion, one that comes up frequently in my circle of autocross and track fiend friends.
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Hi,
Well you are being a little difficult. Nowhere did I say that the alignment specs alone dictated that the car over/understeers. But, in the case of the Boxster with + Camber in Front and - Camber in the Rear, coupled with the Tire size, width, inflation pressure, these
do bias the car (any Car) toward understeer. Add the differing Tires widths, offsets, pressures (not to mention Anti-Roll Bars and differing Spring Rates F/R) and you have a car which absolutely understeers naturally - it simply
MUST!
Also, you seem to be denying that a car even
can be setup to favor one characteristic over another. This is just nonsense. Cars are setup to achieve a desired response on the road and manufacturers (and their Legal Depts.) always favor inputting understeer for safety and to make the car pleasurable to an average, or not so average, driver to drive. It's as much a Marketing thing as a Liability one, it gets the Secretaries to line up to buy one as well as the enthusiast. It makes the car
easy to drive by most people's standards.
If the car is so setup, you must mitigate this natural tendency by altering the variables or driving style to negate or overcome these. You said earlier that a car cannot be setup neutrally and still be safe, but you fail to acknowledge that a car can and is setup to favor one characteristic over another. Everything else is just an Academic arguement which no one made, or disagrees with...
Happy Motoring!... Jim'99