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Roll Centers and Drifting

    Everybody likes a slammed car. Also, most people think that lower is better for autosports. Lowering a car does good things for drifting but after a certain point, it actually hurts more than it helps. The big factor for this is something called "Roll Centers".

    (image not drawn to scale or to any major degree of accuracy)

    The Science

    The diagram above shows the average lowered car. The light blue dot represents the old center of gravity and the dark blue dot is the new. Statically lowering a car doesn't do huge amounts for the center of gravity but it does have a profound affect on the Roll center. The central location of the roll center is the point where the intersecting lines of the car's main control arms. When lowering the car, control arms tend to point upward in a "V" pattern. This change in control arm angle is what causes the roll center to change.

    For the sake of grassroots drifting and simplicity, there is no need to draw these imaginary lines to find out the true roll center or center of gravity. The roll center is simply the point where cornering force/momentum is applied at the car's center of gravity.

    That doesn't make a huge amount of sense at first. Think of the center of gravity as the hinge of a lever. The roll center is simply the point the forces are applied to to move the lever. Like a wrench turning a nut. Your hand would be the roll center and the nut would be the center of gravity. See the difference between the green bracket and the purple bracket in the image above.

    If you choke down farther on the wrench (away from the nut), you can apply more force to turn the nut. That helps you get a loose nut but this in a car becomes massive amounts of body roll. The same spring rates will have different amounts of body roll simply by raising or lowering the car. The lower the car, the MORE body roll!

    The Solution(s)

    The solution isn't simply to raise the car. That wouldn't help the center of gravity. The solution is to fix the angle of the control arms that are now at odd angles. We want to get them back to factory orientation. Or at least as close as we can get.

    The simplest solution is to get stiffer springs and call it a day. But that isn't a solution. It's more of a band-aid.

    There are only two true solutions. Either raise the subframe or lower the attachment point to the spindles of the wheels. In the rear ends of cars, raising the subframe is usually possible. On most cars, raising the front subframe is impossible or would raise the engine and by proxy the center of gravity.

    Most aftermarket companies make simple bolt on Roll Center Adjusters (RCAs). Some are sold in various heights to meet your level of low. The goal is to get those control arms back as close to factory specs as possible. Even a little bit can go a long way as roll center movement as the car is lowered is exponential.

    If your control arms are hailing Hitler, your roll center is too.