Body roll is the axial rotation of a vehicle’s body towards the outside of a turn. Body roll occurs because the compliance in vehicle suspension allows the vehicle body, which sits upon the suspension, to lean in the direction of the perceived

centrifugal force Centrifugal force is a fictitious force in Newtonian mechanics (also called an "inertial" or "pseudo" force) that appears to act on all objects when viewed in a rotating frame of reference. It appears to be directed radially away from the axi ...

acting upon the vehicle.

Cause

Vehicle suspension allows a vehicle’s

wheels A wheel is a rotating component (typically circular in shape) that is intended to turn on an axle bearing. The wheel is one of the key components of the wheel and axle which is one of the six simple machines. Wheels, in conjunction with axl ...

to move independently of its body. This smooths the ride for occupants and cargo while allowing the wheels to stay in contact with the ground over bumps. In a corner, the

range of motion Range of motion (or ROM) is the linear or angular distance that a moving object may normally travel while properly attached to another. In biomechanics and strength training, ROM refers to the angular distance and direction a joint can move be ...

in the suspension allows the vehicle body to lean over toward the outside of the turn as the body tries to continue in a line

tangential In geometry, the tangent line (or simply tangent) to a plane curve at a given point is, intuitively, the straight line that "just touches" the curve at that point. Leibniz defined it as the line through a pair of infinitely close points on ...

to the corner. Softer suspension with more travel will allow more body roll than harder suspension with less travel.

Adverse effects

Body roll allows a vehicle’s centre of mass to move towards the outside of the turn, increasing the load transfer to the outside wheels. This can cause

understeer Understeer and oversteer are vehicle dynamics terms used to describe the sensitivity of the vehicle to changes in steering angle associated with changes in lateral acceleration. This sensitivity is defined for a level road for a given steady state ...

oversteer Understeer and oversteer are vehicle dynamics terms used to describe the sensitivity of the vehicle to changes in steering angle associated with changes in lateral acceleration. This sensitivity is defined for a level road for a given steady state ...

to occur more easily than if body roll was not a factor. Body roll can also be uncomfortable for passengers and cause damage to cargo.

Mitigation

Anti-roll bars An anti-roll bar (roll bar, anti-sway bar, sway bar, stabilizer bar) is an automobile suspension (vehicle), suspension part that helps reduce the body roll of a vehicle during fast cornering or over road irregularities. It links opposite front or ...

are suspension components designed to mitigate body roll. They do this by connecting the wheels at either end of an

axle An axle or axletree is a central shaft for a rotation, rotating wheel and axle, wheel or gear. On wheeled vehicles, the axle may be fixed to the wheels, rotating with them, or fixed to the vehicle, with the wheels rotating around the axle. In ...

with a torsion bar attached to the vehicle body. Body roll can also be reduced by lowering centre of mass of the vehicle body, fitting stiffer suspension springs and reducing the

sprung mass Sprung mass (or sprung weight), in a vehicle with a suspension, such as an automobile, motorcycle, or a tank, is the portion of the vehicle's total mass that is supported by the suspension, including in most applications approximately half of th ...

of the vehicle.

References

{{AutomotiveHandlingNav Automotive suspension technologies

Cause

Adverse effects

Mitigation

See also

References