Incorrectly aligned front wheels can result in a severe reduction in tractor tyre life. Checking tracking and setting it correctly doesn’t take long but could help to save substantial sums in tyre replacement costs.
“A misalignment by as much as 12mm, which is not uncommon, can cause losses of up to 40%,” warns Peter Debenham, Michelin’s technical manager.
With tractors now travelling on roads at faster speeds and for longer distances, front wheel alignment has become a critical factor in front tyre wear.
A new tractor’s pre-delivery inspection (PDI) by the dealer should include a wheel alignment check, he says.
“Many dealers neglect to do this. It can be a big mistake to assume the tractor manufacturer has set up the front axle correctly,” he insists.
“Most manufacturers buy in front axles from a separate supplier and they are not necessarily checked during tractor assembly.”
While the penalties for incorrect wheel alignment can be expensive, the task of ensuring they are correct is simple and relatively cheap to achieve.
All it requires is a spare half hour and a special measuring tool which can be purchased for under £100.
With the steering wheel set straight, the tool is used to measure the distance between the wheel rims, first at the front and then, with the wheels rotated half turn, at the same point on the rims when they are at the rear.
Using the same point on the rims ensures that any deviation there may be due to bends or scrapes does not affect the result.
The difference between these two measurements should not be more than 2mm, says Mr Debenham.
More than this and the adjustment to the steering track rods should be made to put it right. Equal adjustments should be made to both sides to ensure the wheels are not only parallel to each other but also pointing in the right direction relative to the steering wheel’s position.
“In my experience, as many as 20% – one in five tractors – are running with sufficiently poor front wheel alignment to cause premature wearing of tyres,” he says.
“It’s only when the near-side tyre tread starts to wear excessively that is becomes apparent that something is wrong – and even then most farmers assume there is a fault with the tyre rather than the tracking – such is the lack of knowledge of this problem.”
However, Mr Debenham points out that nearside wear caused by misalignment should not be confused with wear caused by road camber.
“The natural pull to the left caused by road will cause wear to the nearside tyre but his tends to be exacerbated when the alignment is wrong,” he explains.
“The driver turns to the right slightly to hold the tractor straight on the road and this results in the offside wheel running straight and the nearside being turned to the right – effectively running at an angle to the direction of travel and causing excessive wear on the tread.”
On older tractors – particularly those that have had a lifetime of use with a front loader – it can be that track rod end joints have become worn which will also result in wheel misalignment which no adjustment can correct. The only solution in this case is to replace the joints.
“At the end of the day, adjusting front wheel tracking so that wheels run parallel to each other is not difficult or expensive. It just makes good financial sense.” insists Mr Debenham.