Lateral Roll Center Position

For LTO application. The attached image shows two front geometries with basically the same roll center height. I have a good understanding of the effect of roll center height change, however will appreciate any information on the effects of moving the roll center laterally left to right. As I understand it, jacking effects come into consideration but not fully grasping what the impact will be to handling / load distrubution when in this specific example where the height is unchanged but moving the lateral location roughly 11 inches further left.

My concern wouldn't be so much the jacking, which may be more dependent on the lower link angle, but the longer the distance to the virtual roll centre the less camber that will be gained/lost in compression/droop and so in roll. While some is desireably, too much will make it difficult to get control of the 'contact patch'as the loading will be moving quickly acros the tread and also affecting the effective scrub radius, which will give a really unpleasant feel through the steering, especially when the surface has bumbs or undulations.

Might be wrong, though.

Hi Richard,

When it comes to the lateral movement of the roll centre, as you point out there will be some effect on jacking, but for the relatively small lateral movements you are talking about here, these won't be significant.

For me, one of the important considerations for lateral roll centre location is more useful to think about by going one step back and actually considering the instant centre positions. Start by considering the lateral (inertial) forces that act at each of the non-sprung centres of mass during cornering. Lateral roll centre migration will result from non-symmetric instant centre vertical migrations (roll, for example).

If you consider the forces applied to the non-sprung masses, and that the centre of rotation for each of these is about the respective instant centre, you can see how the suspension position (either compression or rebound) is influenced by whether the respective instant centre is above of the below the non-spring mass centre of gravity height. Meaning: the direction of suspension movement due to the lateral forces acting on the non-sprung masses can be either compression or rebound depending on the height of each instant centre - and therefore the amount of lateral roll centre movement.

Let me know if that's not clear, happy to draw you out a diagram if it helps 🙂

Thanks for the info Gord / Tim.

I think I understand what you mean Tim in regards to above or below CG. I guess that’s akin to squat / anti-squat concept?

A drawing would be great.

Yes, it's a similar concept. Laterally applied rather than longitudinally.