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roll axis

Glossary “roll axis” Definition:
The longitudinal axis of a vehicle defined by an imaginary line running through the front and rear roll centers.

roll cage

Glossary “roll cage” Definition:
A tubular, cage-like structure surrounding the cockpit of a race car to protect the driver in case of a rollover and to add strength to the overall structure of the vehicle.

rocker arm geometry

Glossary “rocker arm geometry” Definition:
The angle of the rocker arm in relation to the valve stem. Rocker arm geometry is correct when the center of the rocker arm tip contacts the centerline of the valve stem when the valvetrain is at 30 to 50% of its maximum lift.

rocker arm ratio

Glossary “rocker arm ratio” Definition:
The difference between the upper movement of the pushrod, acting on one end of the rocker arm, and the downward movement of the rocker arm acting on the valve stem. Rocker arm ratio is usually around 1.5 to 1 (1.5:1).