Over-steer or Under-steer... that's the question...

[John V]

Originally Posted by MNBoxster

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!

This is where I disagree. I can build you a car with positive camber up front and negative camber in the rear, wider tires in the rear, stiffer front springs and STILL make that car oversteer in a steady state. It's just not as simple as you're making it out to be.

I think you understand what I'm saying and I understand your overall point about having a car that will have the front end lose traction before the rear in a steady state around a constant-radius corner. I guess that just isn't very useful information to have.

[MNBoxster]

Originally Posted by John V

This is where I disagree. I can build you a car with positive camber up front and negative camber in the rear, wider tires in the rear, stiffer front springs and STILL make that car oversteer in a steady state. It's just not as simple as you're making it out to be.

I think you understand what I'm saying and I understand your overall point about having a car that will have the front end lose traction before the rear in a steady state around a constant-radius corner. I guess that just isn't very useful information to have.

Hi,

Again, you're delving into the realm of the Academic here. You may well be able to "build you a car with positive camber up front and negative camber in the rear, wider tires in the rear, stiffer front springs and STILL make that car oversteer in a steady state." I'm not disputing that. Nor do I dispute that there are greater complexities than those mentioned here.

But I don't believe that you can take a Boxster and "build a car with positive camber up front and negative camber in the rear, wider tires in the rear, stiffer front springs and STILL make that car oversteer in a steady state".

The Boxster naturally understeers. This has been both my experience, and many other members' experience. Virtually every Driver Review ever done on the car as well as the view of most Aftermarket Suspension tuners share the same view...

Happy Motoring!... Jim'99

[John V]

Maybe it's a difference between the S and non-S cars, who knows.

I'll happily drive my neutral car and you can happily drive your understeering car and that's just fine.

[z12358]

Just curious, what are the definitions for over/understeering?

Originally Posted by z12358

Just curious, what are the definitions for over/understeering?

Good question, Z! I have used this a few times to educate myself on this topic:

http://en.wikipedia.org/wiki/Oversteer

[GmanMD]

Just thought the following would be interesting to read. It's from Wikipedia:

A car that tends neither to oversteer nor understeer when pushed to the limit is said to have neutral handling. It seems intuitive that race drivers would prefer a slight oversteer condition to rotate the car around a corner, but this isn't usually the case for two reasons. Accelerating early as the car passes the apex of a corner allows it to gain extra speed down the following straight. The driver who accelerates sooner and/or harder has a large advantage. The rear tires need some excess traction to accelerate the car in this critical phase of the corner, while the front tires can devote all their traction to turning. So the car must be set up with a slight understeer or "tight" tendency. Also, an oversteering car tends to be twitchy and ill tempered, making a race car driver more likely to lose control during a long race or when reacting to sudden situations in traffic.

Carroll Smith, in his book "Drive to Win", provides a detailed explanation of why a fast race car must have a bit of understeer. Note that this applies only to pavement racing. Dirt racing is a different matter.

Even so, some successful race car drivers do prefer a bit of oversteer in their cars, preferring a car which is less sedate and more willing to turn into corners (or inside their opponents). It should be noted that the judgement of a car's handling balance is not an objective one. Driving style is a major factor in the apparent balance of a car. This is why two drivers with identical cars on the same race team often run with rather different balance settings from each other. And both may call the balance of their cars 'neutral'.

The full explanation of oversteer/understeer is here: http://en.wikipedia.org/wiki/Oversteer

[z12358]

From the wikipedia article (which was written by who knows who):
"To put things in even simpler terms, when you turn into a corner, oversteer is when the car turns more than you expected and understeer is when it turns less than you expect."

Seems to me one cannot objectively define "overX" and "underX" without objectively defining "X" first -- and X here is "steering". When does the car turn more than you expect? And can different people have different expectations? Is it oversteer if you already expect it?

I know very little on this subject but I liked the 987S MUCH more than the 997 I tested. Much more neutral and controllable.

[Topless]

Originally Posted by GmanMD

Just thought the following would be interesting to read. It's from Wikipedia:
It should be noted that the judgement of a car's handling balance is not an objective one. Driving style is a major factor in the apparent balance of a car. This is why two drivers with identical cars on the same race team often run with rather different balance settings from each other. And both may call the balance of their cars 'neutral'.[/I]

The full explanation of oversteer/understeer is here: http://en.wikipedia.org/wiki/Oversteer

This is so true. How different drivers set up for a corner greatly affects perceived car balance and handling. This is why every car that is driven to the limits of traction should be set up for driver style and preference. John and Jim might (and probably would) drive the same car and one would notice distinct understeer, the other would find the car very neutral to his driving style. Care to guess which one is which??

[MNBoxster]

Originally Posted by Topless

This is so true. How different drivers set up for a corner greatly affects perceived car balance and handling. This is why every car that is driven to the limits of traction should be set up for driver style and preference. John and Jim might (and probably would) drive the same car and one would notice distinct understeer, the other would find the car very neutral to his driving style. Care to guess which one is which??

Hi,

Sorry, but this is not true. Understeer and Oversteer are not nearly as subjective as some here are trying to make it. These are very definite, measurable phenomena.

The definition can be quite simple - Oversteer, the Car steers deeper into a turn than the turn of the steering wheel would indicate and the Rear End will break away 1st, with Understeer the Car turns shallower than the steering wheel would indicate and the Front End will lose traction before the Rear.

But, the reason(s) this occurs are very complex and a combination of many factors from Track (F/R), Tire size and pressure (even Tire Temp), suspension deflection and settings, Body Roll, alignment settings, etc. Several of these are the result of a number of components which if altered, will also alter how the car responds.

All of this assumes the car is driven in a steady state. Change the dynamic of the car, and the handling characteristics will also change.

Now, all this can be quite different when viewed subjectively by a particular driver using their own driving style, but there is still a static tendency which has been built into the car, whether the driver perceives it or not.

The Boxster is setup by the Factory for the Street. As such, it has a slight Understeer dialed into it because this provides safer, more predictable handling (especially at high speed), it is generally more forgiving, especially to a novice or inexperienced driver. But, Porsche also provides optional equipment such as stiffer shocks and springs, anti-roll bars, front transverse control arms with adjustable Caster settings, for those who wish to adjust the car for Track use...

Happy Motoring!... Jim'99