jl4069

Here is an excerpt from Road and Track magazine written by Doug Milliken author of the classic, Race Car Vehicle Dynamics. Its seems rather on target:
PS- I think it would be great if some of the more knowledgable here could add to this list as I think while it is a good start its still rather general:

Handling: The Dynamicist's View
Handling is really the sum of the driver and the vehicle. The driver provides the input and the vehicle responds with feedback. Without an easy way to characterize the driver, we are left to study the vehicle response, or the vehicle dynamics.

To make sense of handling, it is also necessary to define the task. For example, highway driving and racing are very different activities, with different requirements for both the driver and the car. The general question, "How do you like the handling?" can be answered in many different ways. Specific questions applicable to the road and track are needed: "How do you like the high-speed tracking?" Or, "What do you think about the balance under braking? Is it stable when you turn in?"

While all of the car's controls are important (throttle, brakes, gearbox, etc.), the steering is key to good handling. In the 1950s, aerospace-engineers-turned-weekend-sports-car-racers from Cornell Aeronautical Laboratory in Buffalo, New York, came up with a list of handling criteria originally titled "Desirable Vehicle Characteristics." The following is an annotated version of the list:

Steering response to be fast and well damped, with the car showing minimum roll angle and roll/yaw coupling. The car should follow the steering with minimum fuss. This applies to any car at any speed. But it is most important for racing — the interaction between body motions and the steering (i.e., roll steer). Some design factors to consider are low weight and rotational inertia, stiff springs, hard shock-absorber settings and wider, stiffer tires.

Steering ratio appropriate for the speed range and adequate for emergency maneuvers. Race cars require a sensitive touch on the wheel; the steering is fast for catching skids without shifting hands. For the road, the opposite extreme is the "sneeze factor" attributed to Harry Grylls of Rolls-Royce, with suitably slow steering so that the driver can sneeze and not change lanes.

Smooth steering control force with progression in normal driving, definite on-center feel and moderately fast return. Here is one area where the road car is often heavily compromised. A light car with good non-assisted steering will usually give the best road feel.

Minimum steering backlash, springiness and shake. Modern steering systems have eliminated backlash. Minimum steering-wheel vibration is desirable in street cars, leading to the use of rubber isolators, but some imprecision results.

Minimum change in car direction, pitching and control response with road roughness. Street cars deal with much rougher roads than road-racing cars.

Modest aerodynamic and tire/road steady-state stability over speed range. By definition, a stable car will return toward the original path after some disturbance, say, a bump in the road. In the equations of motion, stability has two parts: (1) Understeer and oversteer. They remain roughly constant at any speed. And to make best use of all four tires, balance is important, especially for racing. (2) Yaw damping. It decreases with speed, and is primarily a function of the tires and the wheelbase. Long-wheelbase cars with big tires have more yaw damping. Short-wheelbase cars can feel "squirrelly" at high speed.

High side forces, or ultimate cornering adhesion. One of the easiest and most common measures of "handling," yet only one part of the whole picture. This is good for lateral-g-force bragging-rights for street cars, but rarely used on the road, even in emergencies. However, it is critical for race cars because it is used on every corner.

Satisfactory skidding characteristics: adequate skid warning, gradual rear breakaway and easy natural recovery. With very few exceptions, wide tires have more abrupt breakaway characteristics and are less forgiving for use on the road. In racing, the levels of driving and of concentration are much higher, and cars with less skid warning are still acceptable.

Minimum change in behavior with braking and acceleration. Load shift to the front wheels (on lift-throttle or braking) tightens the turn, while acceleration (except rear wheelspin) straightens the turn. Many of today's street cars have had these "natural" effects tuned out completely by careful design. Steering with the throttle is fun, but too much and the car might be virtually uncontrollable.

To sum up, handling has many dimensions. It's really too simplistic to talk about "good handling" in an overall sense. It's all about compromises and a good balance of handling design factors for the intended purpose of the car. — Doug Milliken

Steve Whitehorn

iTrader: (13)

(Edit - Doh! Should have posted this on the main thread where you are asking about understeer oversteer - never mind)

Here are my thoughts I posted on an earlier thread on the understeer/oversteer thing


Simon
What do you think of the understeer v oversteer thing.
I have been trained in fast road driving, defensive, offensive and tac driving.
This is where I am comfortable, I have very limited track experince. So am not a good track driver
So for the road
My feelings are that for the road the key is how progressive is the grip is lost.
All this is broad generalisations I know
Many cars having large amounts of grip but letting go in an unprogressive way
Many cars having low levels of grip letting go in a progessive way.
Which is why I enjoy scoobs as they have huge amounts of grip but if driven correctly let go very progessively all be it at fairly high speeds in an understeery kind of way

So given that the progresive loss of grip is the key

Oversteer v Understeeer for the road
As you point out Oversteer does give you more more options and is certainly more involving therefore can see the appeal for the track. ('I drive a powerful RWD car, I can handle it, Ive got hairs on my chest etc - fair enough actually)

Back to real world of a wet drab A road Tuesday at 10.00 hours in Berkshire.

However on the road making swift but safe progess from A to B I don't want to play about I want to get there f**king quicky but safely. I have always felt that predictable understeer is better. You kind of need less space to sort it out. What do you think?

People knock understeer but can you see where I am coming from.
Subaru
Huge amount of grip - normally associated with RWD
Progressive loss of grip - normally associated with low powered stuff
When it losses grip - Understeer
PERFECT

Sorry about the ramblings - but always interested to find different points of view from experienced people. Please feel free to disagee

Cheers
Steve
(Understeer for the road fan)




...However as Simon has rightly pointed out. Understeer is engineered into many road cars as the inexperienced will have a tendancy to lift off when they panic a bit. They are far more likely to sort out an understeer moment.

...He also mentioned that oversteer gives one far more options/ability to control a car in that window when you asking too much of the tyres grip.
And this seems to be the favoured option for many people.


So my comments reflect what works for ME on the ROAD. Not elsewhere and perhaps not for other people.

Best wishes
Steve

Hope I haven't put too many words into your mouth SDB - aiming to give a balanced reply

jl4069

Steve,

Thanks for the well thought out posting. Your words remind me very much of John Barkers (the road test editor at Evo mag) writings through the years. Funny enough, before I read your post, I wrote about the similar idea of road space back on the general area postings. I agree that road-space has got to be a key issue, if one is to consider sliding about on the public road.

Which Impreza do you run? Have you found any other 4WD's with a similar level of progressivness and stabiltiy as the Impreza? Maybe the older Audi's, or maybe the Ford Saphire Cosworth? Another car that might be good, though its not available in the UK is the BMW 3series with 4WD- kind of like a modern version of the 525ix that was in the UK a few years back. Thanks again for the experienced view, JL

Steve Whitehorn

iTrader: (13)

Not running a scooby at the moment. Don't want the expense.

Although seriously thinking about a 95 WRX and puting 4/6 pots on the front and getting a close ratio box (like found on RA) into it as the next one. I would probably try and stiffen it up a bit too.

I have been making rapid but safe progress in 1.0 micra for a year now - occasionaly having a play with other more accomplished german marques

I have also been driving a 330Ci Sport quite a bit. - which although a very 'nice' car with a wonderfully smooth power delivery - really leaves me a bit cold. It really grips but and does communicate to a degree, but it dosen't seem to talk to me though my hands, feet and **** like some other cars.
Perhaps it is just me.

Also been driving various S class mercs for work. Although don't get them much above 30/40 most of the time.

The other FWD car I have driven is the EVO and personaly I prefer the Subaru. I would like to try an Escort one day though.

I agree that space/ lack of it is a key factor in road driving in many instances. Spacial awareness, the abilty to judge closing distances, anticipate what other road users are going to go (what space opens up and what closes), anticipate where your escape space is at all times, what is the limit point looking like, inducing a car to that window where you are playing with its grip - what extra space have you/do you require? and so on.

I would even put it as strongly as this - In a way the intelligent use of space buys you your life on the road.

This seems to be an area that is ignored by many other road users that I come across. Although I have noticed that more people do keep a good 2+ second gap now on the motorways than a few years ago.

Anyway rambling now so better go
Best wishes
Steve