O n The front tyres of my one-ton van tend
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to squeal on corners and tyre wear seems to be unduly high; a business acquaintance who runs a similar vehicle says he has not had this trouble and he obtains a higher mileage from his front tyres.
I took my van to a service station specializing in checking steering geometry and various adjustments were made, but the trouble persists. The local distributors of the make have confirmed that the geometry is correct. Can you suggest a cause and a cure?
AThe probable explanation is that the "toe-out-on-turnsgeometry is incorrect. When a vehicle is negotiating a curve, the centre of turn of both front wheels must be the same. The inner wheel must, therefore, be moved through a greater angle than the Outer wheel, so that it toes-out more than the outer wheel toes-in.
The track rod of a steering system is connec
ted to the stub-axle assemblies by arms that are angled inwards an equal amount when the steering gear is set to give straight ahead running. Because a fault in toe-out-on-turns geometry is rare, an appropriate check is not normally made when the steering is tested.
If the toe-out-on-turns geometry is incorrect the fault almost certainly results from one or both arms being of the incorrect length; in some systems there is an intermediate arm which could be of the wrong length. In no case can the fault be rectified by adjustment. You are advised to notify the distributors that you suspect the type of fault described and to request that a re-check of the steering be made to include a test of toe-out-on-turns. A comparison of arm lengths with the lengths of spare arms could readily be made.
Toe-out-on-turns should not be confused with front wheel toe-out when the wheels are approximately in line with the axis of the vehicle. Normally the wheels are toed-in a small amount but on front-wheel-drive vehicles they are generally toed-out; in both cases the initial setting is such that the wheels occupy a straight ahead position under average driving conditions. The length of the track rod or rods can be adjusted to give the correct toe-in or toe-out or, of course, a zero setting.