這是來自Alexander Hagberg 的
Chassis roll can be controlled by altering the position of the roll center. This is done by small changes in the suspension geometry: upper link and lower arms length and positions, as well as widening or narrowing of the track width. The changes will have the following effect:
Raise upper link on the outside: the roll center is raised.
Raise upper link on the inside: the roll center is lowered.
Raise the link on both points: the roll center is lowered, albeit slightly.
Widen track width: raises the roll center.
Longer upper link: the roll center is lowered. The roll center itself will go lower throughout the roll. Whereas, when the upper link is shortened, the height of the roll center has less of a change.
Roll center affects and is affected by many other areas of the car such as camber, shocks, shock springs, camber gain etc. It is therefore important to understand that this change in set-up cannot be considered as an effect of its own.
The rule of thumb:
Higher front roll center:
Decreases chassis roll at the front end of the car. It will make the car under steer off-power. The car will have better on-power steering as less weight is transferred to the rear wheels. Will make the front tires overheat less. The car will have a quicker initial response.
Lower front roll center:
Increases chassis roll at the front end of the car. It will make the car have less on-power steering. The turn-in will be better (corner entry steering) off power. The car will absorb bumps better. The car will have a slower initial response.
Higher rear roll center:
Decreases chassis roll at the rear end of the car. On-power steering will be decreased. Off-power steering (turn-in) will be increased as more weight will stay on the front wheels at corner entry.
Lower rear roll center:
Increases the chassis roll at the rear end of the car. The on-power steering will be increased. The corner entry steering will however be decreased.
Alex’s hot tip:
The quickest and most powerful way to change the roll center is to alter the position of the upper links. On most modern touring cars, this can be done by mounting the link into one of a few different holes in the upper bulkhead clamps. Usually there are three different positions which allows for different lengths of the link to be used. On the upright of the rear suspension, there are usually 2 holes available to allow for a longer or shorter link in the rear suspension. The position of the link can be changed by the use of shims underneath its mounting points. My tip is to start with the kit set-up. Take note of the handling of your car at the different parts of the corner: entry, mid-corner, and exit. Then use the above instructions to determine which adjustment is needed to suit your needs. This is an extremely sensitive tuning tool which can be fine tuned for each track and condition. |
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Thx for share!