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History Suspension 6



Actually, the field of suspension can not really be isolated. Too many factors from other areas also play a part here. Can one e.g., really exclude the downward pressure when cornering, or the possible transfer of vibrations and noises? After all, the suspension has to bring all these influences onto the four, small contact areas where the tyres meet the road and still provide the best possible result, regardless of the driving- or road conditions.

At least in the meantime, the chassis is being paid more attention by the testers. Thus the manufacturers now less often choose cheaper alternatives, of course, they still always have the market placement of the vehicle in mind. As long as a completely adjustable suspension is not available for almost every car on the market, the respective set-up, either sporting or touring, carries a certain amount of importance. It is interesting thereby, that the philosophy changes from manufacturer to manufacturer. Some adjustable suspensions can simply not be made really comfortable.

All in all, as in other systems in the motor vehicle area as well, the trend goes towards applying the more technical solutions from the top of the range models, through the course of model generations, to the lower rated models. Due to the fact that sometimes having fewer differences is cheaper, the more expensive solution, e.g., in on-board computers, is introduced rather quickly into the smaller models.

Over the last years or even decades, the increasing demands on the suspension have been responsible for new and partly also complex solutions. If in the past, the suspension was treated like a poor relation, this is certainly no longer the case. If the accompanying electronics are not consciously put out of use, then the suspension definitely completes the circle of safe motoring. Indeed, also the driving comfort should not be ignored.

What actually, is the extent of the spring travel or, to be more precise, the wheel travel? In some low-slung cars certainly very little. The passengers can hardly enjoy the expensive, height-adjustable spring-suspension units. As a rule of thumb, one can however maintain, the more comfortable the car is, the greater the spring travel is. As a rule, the upper-class models also have more. This is also valid for off-road vehicles. If you've had the opportunity to deal look at the vehicles used in the desert-rallyes (see above picture), then you'll probably know more about their comparatively enormous amount of spring travel.

The problem that this amount of travel has, is to keep the most important wheel parameters constant. This is why, in the case of rallye cars, a particularly long suspension arm is needed, since one cannot take any random suspension and give it a longer travel. Large imparities, e.g., between the upper- and lower wishbones would cause enormous camber differences when compressing or rebounding.

In a normal suspension the caster- and camber values also differ in these two states. This is why, on a wheel alignment bench, a certain amount of load is prescribed. In normal running operation the differences should also not be too great, because too great a deviation from the wheel alignment of 0°, would have a negative effect on the rolling resistance and over a longer period, would cause excessive wear and tear on the tyres. One degree out of alignment is considered to be about the absolute limit.

Did you know, that the wheelbase actually changes depending on the driving dynamics? This can, by the way, best be seen on an off-road motorcycle with it's very long spring travel. And that there are suitable suspensions, that are equipped with an anti-dive for braking actions and also those that prevent lifting when accelerating. Wheels that stabilize themselves in the straight ahead position, the avoidance of vibrations around the center-point of the steering and favourable influencing of the steering forces, these are all achievements made in modern suspension-geometry.

For many years, it was assumed that front-wheel-drive vehicles always had a good bit more weight on the front axle compared with the rear. Some manufacturers have altered the proportions to such an extent, that a ratio of 50 to 50 was almost achieved. Also the apparent low weight on the rear axle of front-engined cars has profited, even moreso when the climb becomes steeper. This is a situation where the front-wheel-drive car is relieved of strain. 03/17


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