Torque steer
Torque steering is the influence of the engine torque on the steering for some front-wheel drive vehicles. For example, during full acceleration the steering may pull to one side, which may be disturbing to the driver. This either causes a tugging sensation in the steering wheel, or else the car veers from the intended path. As the Torque Steer Effect is directly related to the engine torque capabilities this problem becomes more and more evident with high output engines with strong low rpm range torque.
Torque steering may be confused with steering kickback.
Causes
Root causes for Torque Steer are:[1]
- Incorrect sidewall ply design allowing deformation of the tire sidewall.[2]
- Nonsymmetric driveshaft angles, e.g. due to
- Nonsymmetric design of the vehicle, e.g. different driveshaft length
- Transient movement of the engine
- Tolerances in engine mounts
- Different driveshaft torques left to right
- Suspension geometry tolerances
- Unequal traction forces due to road surface (µ-Split) in combination with Kingpin Offset
- Open differentials may not equally distribute the torque between the two driveshafts, due to friction in the side gears etc. The same will be seen if a limited slip differential is used. Either way there is a tendency for the slower wheel to receive more torque.
Ways to reduce the effect of torque steer
Use equal length drive shafts --- this will ensure the angle at which each driveshaft enters the outer CV joint is roughly equal.
If possible try and design the differential axis to be at the same height above the road as the road wheel centre.
Reduce body roll.
If unequal length drive shafts are used consider reducing suspension travel.
References
- ^ Jens Dornhege. "Torque Steer Influences on McPherson Front Axles" (PDF).
- ^ Tony Swan. "Car and Driver 2005 Pontiac Grand Prix GXP".