ksg@houxj.UUCP (K.GRANT) (05/28/85)
It seems several people on the net have been posting detailed technical discussions about how suspensions work. For all us dummies, could someone please explain the basics. For instance, What is camber? How do sway bars help your ride? What does your suspension do when you hit a bump? What else makes your suspension better? Thanks. Please continue the invovled discussions, but explain yourselves. -Kevin
chas@ihuxe.UUCP (Charles Lambert) (05/29/85)
> What is camber? Look at the wheel from the front of the car, with the car standing on a level surface and the wheels in the straight-ahead position. If the wheel is perfectly vertical, that's zero camber. If the wheel is tilted from the vertical, then the angle it makes with the vertical is known as camber. When the wheel is tilted so that the top is further out (away from the car) than the bottom, that's negative camber. The reverse is positive camber. (Just for confusion, the deviation of a road-surface from the horizontal is also referred to as camber.) I'll leave discussion of the benefits of these arrangements to others. > How do sway bars help your ride? They don't make the ride any smoother. Their purpose is to reduce body-roll. A sway-bar connects the suspension on one wheel with that of its mate on the opposite side of the car. Under this arrangement, both wheels can move up or down together without the sway-bar having any influence - for instance, when riding over a ridge in the road - but when the car starts to roll, one wheel going up and the other down, the sway-bar resists the differential movement. This may (I only say *may*) improve handling for the reasons discussed later. > What does your suspension do when you hit a bump? In the steady state, when the car is at rest or moving over a "perfectly" flat road, the compression (deflection, torsion - depends on the design) of the springs is just enough to balance the weight of the car. When the wheel hits a bump it is forced to move upwards (due allowance being made for the flexibility of the tyre) and so is the end of the suspension spring connected to it. At the other end of the spring is a massive object, the car, which is inclined not to move if it can help it. The instanteneous result is that one end of the spring moves whilst the other does not, producing compression in the spring. Now the compression in the spring is greater than the downward weight of the car, so the spring forces the car to rise but at a slower rate than the wheel had to. The problem is, the car moving upwards tends to overshoot, extending the spring which begins to lift the wheel off the road until the car drops back again, compressing the spring again. In a perfect world this would go on forever, much to the detrement of car-control. These repetitive motions are called oscillations, and for a given mass of car and a given strength of spring they occur at a fixed rate known as the "resonant frequency" of the system. So the dampers are built into the suspension to control this. They are basically energy-wasters. The spring loses some of its energy in overcoming the resistance of the dampers, can impart less force to the car and so the car has less tendency to overshoot. > What else makes your suspension better? Depends what you consider better. Softer springs and dampers make for a smoother ride on the straights but they leave the car wallowing around curves. That's bad for car-control because the body and suspension move more slowly from the steady straight-and-level attitude to the steady leaning-around-the-curve attitude and while it's making the transition the steering response is changing, so it's less predictable. Stiffer suspension, that's stiffer springs and harder dampers, cut down this transition period and so the car's cornering response is more predictable. That's where sway-bars help. There are innumerable other ways to alter the behaviour of suspension: adding extra links to alter the attitudes through which the wheel moves; or tie-bars to prevent the rear-axle from "winding up" (on a rear-drive car) under accelleration; changing the geometry of the suspension to lower the "imaginary" point about which the car rolls; etc. etc. etc. What's "better", and how to achieve it, will probably be a subject of heated debate in this group until the day that the net.flamers drop the bomb. Charlie @ the Death Star, IL.