4-bar setup question

[Norm Peterson]

Best answer I can give without more details is that you'll have too much rear axle roll steer (making the car understeer more) and it'll ride a little harder (because as the wheel moves up into jounce as it steps over a bump it also moves forward, sort of "into" the bumps).

To try to put some numbers on the roll steer, a 10* down angle on the bars toward the chassis ends is in the neighborhood of 17%, give or take a few % depending on exactly what elevation a PHB or other main lateral locating linkage is positioned. For comparison, 7% is still a bit high and 3% to 5% is a better target.

In normal to moderate driving you may or may not particularly notice the roll steer, but probably would during more during hard maneuvers (such as slaloms).



Reducing the angle is likely the best way of improving the ride, as it also helps the roll steer. The simplest alternative is to use relatively soft bushings and give away some accuracy of axle location and pinion angle control.

There may be other solutions.

Norm