Anti characteristics theory

Questions:

1.Can you completely prevent the rear spring from extension during braking? (at least theoretically) If yes, explain how

2.What is the maximum anti-squat that the rear suspension of a front wheel drive car have?

3.What is the front suspension anti-dive angle needed to produce 30% anti-dive in a vehicle with CG height of 500 mm, wheelbase of 2600 mm and a rear brake bias of 35%?

4.Should the wheel recede or advance in jounce in order to have good impact performance?

Answers:

1. Yes. Theoretically, it is possible to completely prevent rear springs from extension by arranging the links to have e/d=2*h/l

2.The maximum anti-squat the rear suspension of front wheel drive can have is zero. This is due to the fact that the power from the engine is transmitted to front wheels and the rear wheels have zero throttle proportion factor,which would result in zero force,and thus zero moment produced.

3. Given:

CG height, h = 500mm

Wheelbase, l = 2600mm

Rear brake bias, phi(r) = 35% = 0.35

Front brake bias, phi(f) = 1-0.35 = 0.65

Anti-dive equation for braking,

Phi(f)*(e/d) = (h/l)

0.65*(e/d) = (500/2600)

(e/d) = 0.1923/0.65

(e/d) = 0.2958

Also, tan(theta) = (e/d)

Tan(theta) = 0.2958

Theta = arctan(0.2958)

Theta = 16.48 degrees

Required anti-dive = 30%

Theta = 0.3*16.48

Theta = 4.94 degrees.

4. The wheel should recede in jounce in order to have good imapact performance.

This is possible when the instant centre is:

1. Either ahead and above with respect to wheel centre
2. Or behind and below with respect to wheel centre.