The claim is far from new, but in spite of considerable publicity in the 1990s it is surprising how few haulage operators put in place a preventative alignment programme. With fuel prices in excess of 90p/litre, and tyre prices going up by 20% last year alone, it may now be worth considering this oprtion.
Research conducted by the Transport Research Laboratory, Steertrak, MAN and others has shown the link between wheel alignment, fuel consumption and tyre wear. If just one axle is misaligned by just half a degree, fuel consumption could increase by 3% to 5%. “The increased drag means the vehicle doesn’t pull smoothly, and it soon becomes the one that always sits in the corner of the yard because nobody wants to take it out,” Steertrak managing director Andy Cornish told Tyres & Accessories.
Once in motion, misaligned tyres suffer from uneven wear patterns and an unnecessary build up of heat eventually leading to premature tyre failure. If the axle is slewed back on the off side, then the outside edge of the nearside tyre and the inside of the outside tyre will show excessive wear. This can also be indicated by tyre wear on the steered axle.
Steer-axle wheels can either be parallel to the direction of travel, or pigeon-toed (pointing a little towards one another) at the front edge. This is known as toe-in. Toe-out is where they point slightly away from one another at the front edge. Too much toe-in and equals rapid wear on the outside shoulders of the tyres. Too much toe-out and you get rapid wear of the inside shoulders. A toe out of just 0.75 degrees can mean a tyre is dragged sideways 19.28m for every mile it travels.
further concern is the castor the angle at which the king pin is tilted. The upper end is usually tilted backwards slightly. An excessive angle either way will not affect tyre wear or mileage, but can have a dramatic impact on the way the truck steers. The steering can become unstable and develop a strong self-centring motion or no returning action at all. “Once the tyre tread and shoulder wear pattern has become so uneven as to be noticeable, in many respects it is too late. You can rescue the situation as far as fuel consumption is concerned, but as for the tyres the damage has already been done,” Cornish explained.
The best course of action is to ensure that alignment is checked regularly. Of course, Cornish recommends the Steertrak fleet programme as a cost effective method of control. Steertak technicians are contactable on a free phone number and can carry out measurements and adjustments on site, he adds.
The alignment process starts by hanging self-centring gauges on the front and rear of the vehicle, which allow the true centreline to be determined. This approach does not use the back axle as a reference point because it is not unusual for this to be misaligned.
A laser is then attached to each wheel in turn, mounted on a special adapter, which is adjustable for different size rims. The wheel rim run-out needs to be eliminated to calibrate the equipment to the stub itself, as the tyre and rim are not an accurate enough reference point. Working progressively around the vehicle, readings are then taken from the front and rear by projecting a laser beam over its entire length. From these readings the steering geometry is then calculated and adjustments made where necessary.
Steertrak has 14 engineers providing nationwide onsite service, round the clock, seven days a week, all year round. They service 8000 customers. But what does it cost? For one off prices an engineer will check and adjust alignment on a single steer-axle for £65, and a twin steer for £110. According to Cornish, this normally pays for itself within weeks and fleet users can expect a discount of up to 25%.