Torque steer

Torque steer is the unintended influence of engine torque on the steering, especially in front-wheel drive vehicles. For example, during heavy acceleration the steering may pull to one side, which may be disturbing to the driver. The effect is manifested either as a tugging sensation in the steering wheel, or a veering of the vehicle from the intended path. Torque steer is directly related to differences in the forces in the contact patches of the left and right drive wheels. The effect becomes more evident when high torques are applied to the drive wheels either because of a high overall reduction ratio between the engine and wheels, high engine torque, or some combination of the two. Torque steer is distinct from steering kickback.

Root causes for torque steer are:

The problems associated with unequal length driveshafts is endemic to the transverse engine layout combined with an end mounted transmission unit; some manufacturers have mitigated this completely by mounting the engine longitudinally but still driving the front wheels - this indeed was the solution adopted on the earliest front wheel drive Citroens. Early Renault front driven models such as the R4, R5 Phase I R12, R18 and certain R21 models also adopted this layout, as does Audi to the present day in its midsize models upward. The key disadvantage is packaging; in the case of Audi, which mounts the power unit ahead of the front axle line, this compromises handling by going against the perfect 50:50 weight distribution. This configuration does however facilitate the easy addition of all wheel drive - Subaru also uses the overhung longitudinal engine for the same reason, but mitigates the problem of unbalanced centre of gravity by using a "flat-four" boxer engine. Renault, on the other hand placed the engine behind the front axle line, but this compromises interior packaging since it forces the engine further back towards the firewall.

Rear-wheel-drive vehicles still are affected by torque steer in the sense that any of the above situations will still apply a steering moment to the car (though from the rear wheels instead of the front). However, the torque-steer effect at the rear wheels will not send any torque response back through the steering column, so the driver will not have to fight the steering wheel.

This page was last edited on 22 May 2018, at 00:57 (UTC).
Reference: under CC BY-SA license.

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