<VV> Oversteer

kenpepke at juno.com kenpepke at juno.com
Sat Dec 8 08:11:32 EST 2007

 Smitty Says:  Ken youse is a mild driver.  At street speeds and cornering at 25-30 mph 
they do understeer.  Bit there is a transition point as speed increases where they ALL 
shift into oversteer.
I am a mild driver ... but in earlier days I raced both EM & LM on tracks.  I went on to build 'figure 8' cars and then to design and build late model short track oval race cars.  

When I said ' they under-steer much less than front engine cars; that is to say they are much closer to neutral steering' I am referring to chassis design and the engineered 'set up' the cars came with from the factory ... not to a driver going into a situation 'way over their head' or a car in poor repair or even throttle over-steer.  

Those who have seen the GM film 'Car on Trial' viewed the skid pad tests in which they were able to accomplish a .72 G lateral acceleration.  During that test they continually held the steering wheel to the left.  As the car approaches neutral less and less effort is required to hold the steering wheel to the left.  As they did not tell us what that effort was at .72 G we do not know how close to neutral they were getting.  At no time was it necessary to turn the steering wheel to the right to maintain the circle!

It is possible, by arranging suspension mounting points and spring rates to make any car have your choice of under-steer, neutral, or over-steer characteristics regardless of weigh bias.  It is also possible to 'spin out' or 'push out' any kind of car by applying more lateral acceleration to one axle or the other than the maximum traction that is available for that axle.  For most drivers these conditions occur much to their surprise ... they are even more surprised if they miss having an accident.  Driver emotions can determine a point at which they feel the car has shifted into understeering.  That point will vary from driver to driver so it is not acutally reflecting a vehicle's handling characteristics. 

I am not sure why but most drivers are most comfortable in a car that under-steers.  The closer to neutral the car becomes the more uncomfortable the driver will become.  Hardly anyone this side of an experienced race car driver will be comfortable with even a neutral car.  The point is most will feel a car is over-steering long before it gets to even a neutral feeling.  I don't think anyone would want a car with a high degree of over-steering in the 'set up.' 

Throttle over-steering is a completely different situation.  Watch some racing at dirt oval tracks where they have the front wheels turned to the RIGHT in a left turn!  Or watch a kid in a '68 427 Ford doing 'donuts' in a parking lot.  Those cars put to a skid pad test would actually under-steer!  
Ken Pepke 
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