The paper develops theoretical formulations of steering-adjustment parameters (camber, castor, toe-in, toe-out, steering axis inclination) for a 10 t commercial truck such that steering performance and driving stability are improved. Optimized adjustments are then evaluated in driving trials. The results compared favorably with theoretical predictions. The following conclusions were drawn:1. The expected conformity between theoretical and experimental results was confirmed.2. The importance of the different steering adjustments depends upon the driving conditions.3. Adjustment of steering parameters for front-wheel driven axles produces changes in stabilizing forces. However, improvement in either steering or stability results in impairment of the other characteristic; hence, an optimization must be attempted.4. The testing methods used in driving trials could be effectively used on unmodified vehicles above 6 t total weight.5. Optimal steering adjustments were made on a truck which produced significant improvements in steering and performance.6. Results indicate that radial tire wear can be reduced by setting camber at 0°.