But then what’s this roll-center thing? The “Roll-Center” (English term, in Portuguese “Center of Rotation”) is the point in the space over which the axis rotates. As a rule, when we apply the suspension and reduce the body level to the ground, we also lower the Roll-Center, in a greater proportion than what we lowered the bodywork.
The way to calculate it is that it’s not that direct. Each suspension geometry has its own way of determining the “IC” (Instant Center in English, Instant Center of Rotation in Portuguese) and consequently the RC (Roll-Center).
1 – Determine CI in a suspension of overlapping triangles
2 – Roll Center in a suspension of overlapping triangles
3 – Determine CI in a McPherson-type suspension
4 – Roll Center on rigid shaft
Roll Couple is called the Roll Center distance to cg (Center of Gravity), and it is not advisable to be increased too much. The torque exercised from the bodywork on the suspension arms increases dramatically, increasing the tension in the body components. The Camber he earns in suspension work for the perfect attack on the curve we want will no longer be the same.
And who suffers from this? The tires! This effort combined with a larger game between the screwed-up body connections, leading to constant unwanted re-grips in case of more severe driving.
This adjustment of the position of the arms of our “wheels” are justified by numerous reasons, some with influences in others. We could simply adjust the RC as close to the CG as possible and expect an approximate behavior of the perfect, but here come several variables such as suspension geometry, alignments, mass distribution, tires… Phew even tired!
One of them, very usual, is if we want him to have an oversteer or understeer behavior, as we show you in this image.
If the RC on the front is taller than in the rear, they will behave oversteer, or the other way around, if it is lower than the rear.
Conclusions?
It is no accident that the cutting edge of engineering development lies in motorsport. After developing with all these details, they have another team with unparalleled experience where they take into account every detail, for each track and for each rider.
On our wheels, I’d say we can explore anything we want too, why not?
However, NipponLAB advises you to always correct the position of your car’s suspension arms whenever you lower it. You’re going to like the result!