The ABC of tyres on the farm
LIZE HAYWARD, GROUP PUBLIC RELATIONS MANAGER, GOODYEAR TYRE & RUBBER HOLDINGS (PTY) LTD
Knowing how to get the best out of your farm tyres will not only contribute towards enhanced safety, but will also reduce operating costs and limit damage to soil and crops.
Valuable driving tips
Farm driving brings with it a whole range of operating conditions – everything from ploughing fields to towing trailers on tarred roads. And as varied as these situations are, there are some important rules to follow.
As far as tyres are concerned, some of the key points are to match the type of tyre to the intended application (mud or soft sand); sticking to the vehicle manufacturer's guidelines in tyre size and specification; and more crucially, adapting the tyre inflation according to the load and operating terrain.
It's simply the air in the tyre that enables it to bear the load and tyre manufacturers determine the maximum load ratings for each tyre, within specific speed limits.
Match tyre inflation to tyre load
Heavily loading a vehicle without adjusting the air pressure will result in excessive tyre damage and wear, drastically reducing its operating performance and lifespan.
An overloaded or under-inflated tyre will deflect or bend excessively under these conditions, potentially cracking in the upper section of the sidewall and wearing quickly on the outer shoulders. Under-inflated bias or crossply tyres are especially prone to sidewall buckles when exposed to high-torque driving conditions, thereby damaging the carcass of the tyre. Very low pressure may also lead to the tyre slipping on the rim, tearing the valve off tubed tyres and generally damaging the tyre’s beading.
In turn, over-inflation makes the tyre too rounded, with the wear mainly occurring in the centre. It also reduces the tyre’s contact area with the ground, negatively impacting on traction and increasing the chance of wheel spin that damages the tread and rips up the soil.
If you’re forced to drive a tractor on the slope of a hill, the inflation pressure of the tyres should be increased by up to 30% from the base pressure (depending on the gradient) to provide greater stability. This applies to the rear drive tyres only – the single down-slope tyre if driving in one direction, or both if working in alternate directions.
It is vital to remember to compensate for reduced or increased pressure when altering the operating conditions, such as hitching a trailer or implement, or driving on a tar road at speed.
Click on http://php.grainsa.co.za/documents/SAGraan%20Febr10_Tyres.pdf for the complete article.
Publication: February 2010