Rear roll steer ?

[pav8427]

I know that if a person has rear steer that if anything you should have roll understeer.
Short of running anything through a susp. program, is there a actual
amount (ie. 1/8" difference in wheel base between left and right) that would be considered 'max'?
I know every rig will react different and depending on the application, some is better than none and more is worse than some, and anything would be better than oversteer.

Thanks,Doug

[Norm Peterson]

Somewhere around 3% roll steer is probably appropriate for most PT-oriented cars (the axle steers 0.03° for every degree of sprung mass roll relative to the axle). Coincidentally, that 1/8" difference-in-wheelbase-during-roll figure agrees quite well with 4° roll (not including tire deflection effects) and a 60" track.

The geometric construction of the axle's own roll axis isn't particularly difficult, and can be done in a simple spreadsheet. Its slope is the rollsteer %. Just keep in mind that it will vary a bit in both directions (from more U/S to less U/S or even going slightly O/S under extreme braking) as rear ride height varies with changes in the loading (e.g. passengers, trunk load, accelerating, braking).


Norm

[Bow Tie 67]

I have a question, my wheelbase is not equal on both sides. I have aligned the front end ( although the right front could use more + caster ) and aligned the rear end dead even with the front tires.

I'm thinking if I add more + caster on the RF it will increase the difference between wheelbase side to side.

Currently the W.B. measures driver side 107 29/32" WB and the passenger side reads 107 23/32".

Camber 3/4* both sides

Caster 2.8* left & 2.5* right Can this slight difference change the W.B. by a 3/16" ????????

Is there an acceptable limit on W.B. difference while static? Or am I splitting hairs?

I would assume that depending on which side its " staggered to " would decide which turn direction the car would react to better.

Matt