Author of Race Car Vehicle Dynamics article
 

For all those interested in Vehicle dynamics, I just posted a portion of an article written by the author of Race Car Vehicle Dynamics, to the driving dynamics area of Scoobynet here:

Here's a snipit I found interesting: "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."

I'm curious if wishing for "gradual rear breakaway and natural recovery" is really the only option a engineer should design into a car's handling; that is I wonder if as with many cars, a gradual *front* breakaway might in some on-road cases be preferable, if, and this is a big if, the front losses grip very very slowly and in such a way that the slight use of throttle easily brings the nose back into grip??? I say this as opposed to the scenario where the rear end loses grip (oversteer) and you apply opposite lock and your car winds up hitting another car going the other way, or a tree or a wall? I mean we are talking here about the public road. I suppose what I'm asking is: for the public road, what is a safer handling characteristic if a car is to be driven quickly through corners, gradual oversteer or gradual understeer, provided that both cars are light, great handling- well damped, have poise etc. I think it would make a darn interesting experiment.

http://bbs.scoobynet.co.uk/showthrea...10#post3564110

Thought I'd give this topic one last chance for a chat.

Power understeer is almost universally considered safer, hence why it is present in almost all production road cars(maybe the Noble and TVR marques are an exception, even the 996 and 360's are understeering monsters these days), oversteer is gernerally considered 'a bad thing' in a road car driven by Mr. A.N. Other and is almost always much harder to provoke than understeer.
C

Unless you're a Volvo driver. Came across some site a couple days ago that tried to explain that RWD was MUCH safer than FWD because U/S is more dangerous than O/S. :brickwall

Go and play on a skid-pan. You can get on a course at Hixon for about £45. I found RWD was much more fun with plenty of warning and controllability when things started to go wrong. You could push FWD quiet a lot more before losing it, but when FWD went, there was little you could do to put it right.

If you remove driver car control from the equation.. (assume the most skilled driver on the planet).. oversteer is safer than understeer as it affords you much more control over the car.

The problem is that (For road cars) you can't remove driver car control from the equation, so designers realise that due to the added ability to control the car when in oversteer, many people are afforded the opportunity to make things much worse due to controlling it wrongly! So at least with understeer, there is less chance of making things worse. This, along with the fact that instinctively slowing down (by lifting or braking) is likely to be safer during understeer than oversteer, is why understeer is considered safer in a road car.

All the best
Simon

Watching Formula Women stacking RX8s while 'recovering' from mild looking tail out moments sums it up for me:)

I lost the tail of my (ex) Passat while taking a roundabout too quickly for the road conditions. I reversed steered to correct, and then the car just whipped into an astounding spin, travelled a large distance in spirals, and tore off the rear wheel on the kerb.

I thought I was in control. The experience of being so totally out of control was very sobering. The transition from stable to spin was virtually instantaneous, like a big spring letting go.

If it hasn't happened to you yet, be very afraid ;-)

I don't think anyone gets it right the first time they have a tail out moment, but by finding a safe place to play and getting it wrong a few times you start to develop the right reflexes.

Usually the things that get you are not winding the lock off again fast enough, and/or braking/lifting off suddenly.

Simon,
But don't you think that even very good drivers, simply cannot always have enough room on a public road to do such sliding? I mean how much car control can one exhibit on a thin b-road with other cars around? Or are you saying that indeed such oversteering need not take up that much road space? Again the types of situations I'm speaking of could be, a blind changing radius curve with standing water on the other side, an errant animal that pops up from seemingly nowhere, etc. Thanks, JL

hi JL

What I'm saying is.. when the animal jumps out in front of you, or when things start going wrong, oversteer affords a skilled driver more opportunity to control the car and avoid these things.

This also applies to the amount of room it takes up.. if you're understeering across the other side of the road and into a ditch you're using up all of the available room and more.. but there is more chance that the skilled driver could have controlled the car and avoided using up all that room.

Again, important to note that I'm not saying road cars should oversteer, I'm just making the point about the pure physical situations.

All the best

Simon

Simon,

Good points. Of course I also think its worth noting that while indeed the oversteering cars would give a experienced driver more options, that the same car in other kinds of challenging conditions cheifly those involving slippery roads, would be more of a handful. I suppose it really comes down to horses for courses specific conditions requiring speciifc handling attributes.

Simon, also take a look at Steve Whitehorns responce over in the dynamics area http://bbs.scoobynet.co.uk/showthread.php?t=348011 Thanks, JL