12 March 1999

Tubeless rubber takes over

Theres little point having

the power if you dont have

the traction. We start our

tyres and wheels special

with a look at the benefits

tubeless tyres can offer

TRACTOR tyres without tubes have been available commercially since the late 1980s and now, 10 years later, they have taken over most of the market.

Some estimates put the tubeless share of the UK tractor tyre market as high as 90%, and Andy Wyatt thinks this is probably correct.

Mr Wyatt, sales manager at Fieldens, the Suffolk-based agricultural tyre and wheel specialist, has seen a big rise in the number of tractors equipped with tubeless tyres.

"When I joined the company in 1990 about 90% of the tractor tyres were used with tubes and only 10% were tubeless, but the situation has changed quickly and I would guess that the market share figures have reversed.

"It is a logical trend. Tubeless tyres are a better deal for the customer and we always encourage those who still use tyres with tubes to switch to tubeless," he says.

Paul Condle, agricultural tyre specialist at Michelin, agrees that tubeless tyres offer advantages, including lower cost. This is because they avoid the cost of the tube, which is about £30 for an 18.4×38 drive wheel. Running costs are also likely to be lower because of a saving in replacement valves.

"Valve damage is a significant factor with agricultural tyres," says Mr Condle. "Dealing with the problem is generally less expensive and easier with tubeless tyres."

The biggest benefit of tubeless tyres, the experts say, is the reduced risk of punctures. This is because chafing between the tube and the outer casing is a significant cause of punctures and can occur when air or dirt is trapped between the tube and the casing.

Chafing is also caused by using tyres and tubes with less than the recommended inflation pressure, which is further compounded by the faster speeds of modern tractors.

"Another reason why tubeless tyres tend to have fewer punctures is that they do not have inner tubes with too many old repair patches," says Mr Condle. "Obviously you can stick a patch on a tube and put it back on the wheel, which is cheaper than buying a new tube, but if you have too many repairs on an old tube the risk of punctures increases."

Some farmers prefer using tyres with tubes because they think punctures are harder to repair in a tubeless tyre, but according to Mr Condle this is a myth. he maintains a tubeless tyre puncture can often be plugged from the outside, without removing the tyre.

"When tubeless tyres have punctures the air loss is often slow enough to allow the driver to get the tractor out of the field and back to the yard, where it is easier to repair. Air loss is often much faster from a tube because the tube is under tension, which helps to open the hole and let the air out. That can land you with all the problems of a repair job in the field.

"I am sure the trend towards tubeless tyres will continue. Manufacturers are producing them in a wider range of sizes, and they are now available for row-crop wheels and in many implement and trailer sizes. Cross-ply tyres with tubes are still produced for Third World countries which prefer their tractors with a really basic specification, but tubes are fading out of the picture in countries such as the UK." &#42