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

[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

[jaykay]

.....just to jump in

After a long time on stock S roll bars am contemplating a change. I feel that the car does not turn in sharply enough and lacks front end feel in turns. There is very little oversteer unless it is wet or I have cold tires.

I am on: 18s along with Michelin PSS (for the street); PSS9s; all three strut braces; adjustable rear toe bars. Tire pressure is 30 to 31 up front.

I was considering a change to: both M030 bars and urathane bushes; camber plates to get the top of the front struts solid.

Are there other specific bushings I can target to get some better driver feedback?

[thstone]

Originally Posted by jaykay

.....just to jump in

After a long time on stock S roll bars am contemplating a change. I feel that the car does not turn in sharply enough and lacks front end feel in turns. There is very little oversteer unless it is wet or I have cold tires.

I am on: 18s along with Michelin PSS (for the street); PSS9s; all three strut braces; adjustable rear toe bars. Tire pressure is 30 to 31 up front.

I was considering a change to: both M030 bars and urathane bushes; camber plates to get the top of the front struts solid.

Are there other specific bushings I can target to get some better driver feedback?

The hydraulic power steering only sends a limited amount of feedback through the steering so a Boxster will never feel like a go-kart or an air-cooled 911 in terms of steering feedback.

But reducing/tightening up any of the slop in the front suspension will certainly help. But I worry that it may not completely solve your issue.

A Boxster Spec car (with 255's in front and adj GT-3 sway front/adj sway rear) has huge front end bite into corners and provides ample mid-corner feedback so you might want to head in this direction by increasing front tire width, stiffen the front sway bar, and soften rear sway bar.

Find someone who will let you drive their Spec Boxster to get an idea of what it feels like. And yes, I'll offer a drive in my car if you want to come to Cali.

[jaykay]

Originally Posted by thstone

The hydraulic power steering only sends a limited amount of feedback through the steering so a Boxster will never feel like a go-kart or an air-cooled 911 in terms of steering feedback.

But reducing/tightening up any of the slop in the front suspension will certainly help. But I worry that it may not completely solve your issue.

A Boxster Spec car (with 255's in front and adj GT-3 sway front/adj sway rear) has huge front end bite into corners and provides ample mid-corner feedback so you might want to head in this direction by increasing front tire width, stiffen the front sway bar, and soften rear sway bar.

Find someone who will let you drive their Spec Boxster to get an idea of what it feels like. And yes, I'll offer a drive in my car if you want to come to Cali.

Thanks, Tom I will definitely take you up on that! I may be out there looking for work soon!

Would just the GT3 bar upfront while leave the stock S in the rear provide a reasonable balance and starting point? I know many do it and it is all a matter of personal taste but I don't want to get into too much under steer......perhaps it wont be an issue as I am not on the limit at the track. I am just after some bite..

I am on 225s up front (265s rear) and it may be a while before I am able to source the right sport classic II wheel to handle the 255 tire. I think this may be 911 size somewhere in 993 996 18" offerings.