I have watched a few videos before this one about roll centres and it didn’t fully click. You did a great job to explain this in a clear and logical manner. Now I get it! Thank you so much
Thank you so much!!! I watched so many roll center video these days. This one with the dynamic arrows to illustrate, plus the scenarios really made it the easiest to understand. Thx
also one thing that is not mentiond about roll centers is they are not static as on the paper but as soon as the car starts to bump squat and lean in a turn or a slight change of ride hight makes the roll center to change and move around up down sideways. the picture is just a static formula done during setup to make sure roll center is in theory in the right place compared to front as they rooling around roughly the same axis like a boat that tossing back and forth front and back need to be in sync or the boat or this case a car will act as if its trying to brake itself apart.
Pink Floyd I feel it :) That was an excellent explanation on roll centre. I race on road only these days. But sometimes depending on the traction at the track a higher roll center will give more grip especially on the initial turn. I believe that is because the force applied to the tyres are higher at this point. Maybe on a lower traction track a lower roll center works because we need the car to roll to create more traction. IMO. Please correct me if I’m wrong.
Yeah thats about right. The main difference and the simplest way to explain this is with a higher roll center more force would initially transfer from the inner tire to the outer tire. With lower roll center the forces between the inner and outer tire will initially be more balanced.
Great job Max. Very well explained. After watching this and other vids again and again it slowly makes sense to me. However I am still wondering if its possible to totally fuck up a car by roll center setup. For instance on cars of the major brands like Kyosho, Mugen, Mayako, Asso, Sworkz and so on, is it possible, for instance, to set the roll center that low ending up with positive camber gain? Or are the setup options always on the save side on a well designed car?
For Kyosho and Mayako I don't think the roll center setup can be totally fucked up. Mugen, Asso and Sworkz on the other hand have very wide tuning range and the window where the car works consistently is narrow. And currently Mugen and AE run a positive camber gain in the rear thanks to the super long link.
The reason why the car is traction rolling is because the car is resisting roll geometrically. This means that the forces in the linkages will want to raise the car up and then we see that traction roll effect. When the roll center is lower the car is not resisting roll geometrically so the car is allowed to roll under the suspension and the forces through the linkages wont be there to lift the car up as much. Basically the angle of the upper link being higher will tend to want to raise the car up.
Roll center is the point which the center of gravity tries to roll around. Center of gravity is the same point in both ends but the roll center is dependent on the suspension geometry in both ends. Now to make your car work properly you want the rear end and front work in harmony while they roll. This doesn't mean that both ends have exactly the same roll center rather both ends need to be tuned so that the roll on each axle matches the grip on each axle. Another way to try and think about this is roll axis meaning an axis drawn connecting both the front and rear roll centers. If the axis is in a really weird angle your car will roll in a very weird angle.
