rear indipendent suspension caster

[UBYVISI]

thread800-445691

I read that rear caster would affect car balance, maybe even in case racing one, as I understood by a very clear post, more caster with the same convention as for front, adds more oversteer and vice versa. Can someone explain me the mechanism?

Thanx a lot

 

[cibachrome]

Simple: The rear caster trail adds an extra moment around the rear uprights. It is reacted by a toe link or a bending something. If caster is + (as in front convention) then the Fy induced moment toes the rear wheel outward just as it would if it was in the front. Only now it's an oversteer effect instead of an understeer effect. Statistics show that a lateral force understeer compliance effect is prevalent out there in parking lots. Lateral force oversteer compliance is usually found in solid axle trucks. There is a ride and durability element to this, though. Spindle offset is another option for inducing this compliance. The spindles are not on the steer axis if you accept that there is a 'steer axis' on an unsteered rear suspension. Just break a toe link sometime and see what changes !

 

[moon161]

I have a 82 Benz 300TD with rear steer problems until I replaced all the rubber in the rear suspension. I has a rear subframe with semi-trailing arms. It was a laggy oversteer that had the rear end wanting go down the crown of a road, oversteer on a cloverleaf and the presssure wave of a truck passing you would point the rear end away, so the net effect was like being pulled into the trucks path. A rear tire flatted and I barely kept control pulling it over. I flatted a rear tire last week and it was nothing at all to stay in control with the new bushings in place.

 

[NormPeterson]

Simple: The rear caster trail adds an extra moment around the rear uprights. It is reacted by a toe link or a bending something. If caster is + (as in front convention) then the Fy induced moment toes the rear wheel outward just as it would if it was in the front. Only now it's an oversteer effect instead of an understeer effect.

As in early/prototype examples of that Shogun creation before somebody figured out what was going on.


Norm

 

[UBYVISI]

Thank to all who replied. I now have it confirmed, I thought there was something more due to tyre behaviour.

Once again thank to all.

U