Auto Gossip

Press, Volume CIX, Issue 31974, 29 April 1969, Page 19

Auto Gossip

by

A. J. P.

Under And Over Many motorists, I find, do not know what understeer and oversteer mean, although when it is explained, they often admit that they have experienced both on occasions. Basically, the term describes which end of a car starts to lose adhesion first when cornering. In an understeering car the front starts to go first. On a corner, therefore, the front of the car will tend to run wide, even carry straight ahead in severe cases, and the driver has to I turn the steering wheel a considerable amount to make the car turn a lesser amount In an oversteering car. the back wheels tend to lose adhesion first, the rear end of the car swings wide. and. in effect, the car turns more sharply than the driver might expect from the amount of lock he puts on. In severe cases, if no correction is applied. the “tail hangs out” to such a degree that the car goes sideways, and even spins. Demonstrated Understeer and oversteer can often be seen demonstrated on a racing circuit: the car that sledges ahead on a corner although the front wheels are locked over is understeering: when the tail of the car swings wide and the driver has to apply opposite lock it is a case of severe oversteer. All cars are designed to be basically understeerers, as this makes them more stable in a straight line —they naturally tend to run straight on. But as cornering speeds rise, the characteristics change to neutral the car goes where it is pointed—then to oversteer. The rapidity of the change and the cornering force necessary to

bring it about largely gov-i eras how well the car I handles. Ideally, a car should have slight basic understeer • for stability, neutral characteristics to high cornering • speeds for ease of control, and the oversteer should ap-i pear gradually and progres-' sively again for ease of control and safety. Alter Pressures I To a considerable extent, lone can alter the understeeri oversteer characteristics of a ; car by altering front and rear • tyre pressures relative to each other. Raising the pressure in a tyre makes it retain its grip longer, so increasing the pressure in the front tyres will tend to reduce understeer. Increasing the pressure in the rear tyres only will reduce oversteer. Conversely lowering the pressure will reduce the grip: reducing front tyre pressures will increase understeer, or lessen oversteer. In many cars a change of two or three lbs in pressure will have a marked effect. Preference Personal preference comes into it, of course. I dislike too much understeer, and usually find that running the front tyres about two lbs above the rears adjusts the car’s handling to my liking. Tyre pressures, in fact, are far more important than most drivers realise. A colleague ; came to me a few weeks ago. : for instance, and complained ; that his modern car rolled a; lot on corners when he was

on a trip. I advised him toi raise the tyre pressures by three to four lbs all round,! and he now reports roll-free cornering and much im-i proved handling. Most Important Then there was the driver, who read in a road test that a car he was interested in ; understeered a lot. “But this , is not important at the speeds • we travel at. is it?" he asked i me. Make no mistake, it is j always important. In slip- • pery conditions you can en- ; counter severe under or oversteer at not much more than; •20 m.p.h. And in an emergency knowing your car's understeer-oversteer characteristics could make an . important difference. Quote of the Week "Italy, Germany. France, and Belgium certainly have their share of 40 m.p.h. tumblers, but these either don’t see the flash of your lights as you come up behind them to overtake (in accordance with the nature of 40 m.p.h. fumblers) or register the information and move over. In England, on the other hand, if you come up behind some-; body ambling slowly along—and there is no reason why he 1 shouldn't, provided that he! doesn't take up the whole road in the process—and if you flash your lights at him in a friendly way just to let him know you’re there, he sometimes goes mad when you’ve got past, flashing his lights, sounding his born, or even complaining to the police about dangerous driving.” —From an article in the “Motor” on excitable and incompetent drivers.