Caster allows the front wheels of a vehicle to self-centre when the car is moving. It’s a bit like how a shopping trolley works. When you push forwards the wheels self-centre, slow down and you can manoeuvre around obstacles with ease. By giving the car extreme caster you induce an affect called ‘wheel shimmy’. This is where the front wheels can move from side to side rapidly. At the other extreme, give a car too little caster, and you can induce over steer, making the car feel ‘nervous’ and ‘skittery’ to drive. Negative caster will reduce the car’s straight-line stability, but will increase steering as you turn into a corner.
Positive caster slows the steering response at the initial turn in point. Negative caster will have the effect of making the car more stable, especially on straight-line stability over negative camber, by improving it. With some cars you are provided with two sets of steering knuckles as standard. These offer distinct variations on caster trackside to give the car two very different handling characteristics on track. Again it’s about trial and error, and varies depending on the type of track you can run on. Also remember that what may work for you, might not for others, so if in doubt… try it out!
Terry Crew – Reality Racing