Farm tractors are fairly narrow. When used in the forest, the front and rear wheels should be placed in their widest position. The increased width improves side stability. Row crop tractors with narrow front ends can not be used in the forest.
The weight of an attachment or trailer makes the tractor light in the front end, which makes the tractor difficult to steer. Front end weights help to keep the tractor in balance.
Tractors are also prone to backwards roll over. The risk of roll over is higher when traveling up hill, because the front end is already much closer to the plumb line of the tractor . A roll over can happen in a couple of seconds, even when the tractor is moving at slow speed. Uphill slopes must be avoided, especially when skidding or when pulling a trailer. The trailer tow hook should be mounted low and under the tractor.
The combination of tractor, the attachment and the load should put at least 30% of the total weight on the front axle. Generally speaking, when winching or skidding loads, the tractor will require front end weights.
FRONT END WEIGHTS
Some tractors have more weight in the front than others. A tractor with a front end loader is heavier in the front end, and filling the loader bucket with dirt improves the weight distribution even more. The rule of thumb for adding weights for stationary tractors is that if the attachment is short and light add front end weights equaling half of the weight of the attachment. If the attachment is heavy and long, such as a wood processor, add 60% of the weight of the attachment to the front end. This rule does not apply to tractors that are moving or pulling a load.
While skidding, a farm tractor often becomes light in the front end due to the weight of the attachment or the resistance of the load. This makes the tractor difficult to steer andicreases the risk of roll over. Front end weights will help to stabilize the tractor.
For skidding or pulling a trailer with a 2WD tractor, the rule of thumb is to add 10 lbs of front end weight for every horsepower of tractor engine power. For example, on a 40 HP tractor one, add 40 x 10 lbs = 400 lbs of front end weights. This assumes "average" conditions and tractors without tire chains. Tire chains increase traction on inclines. To compensate for the increased traction, add front end weights to reduce the risk of tractor roll over. Some experimenting may be necessary to find the right amount of weight for your tractor and terrain.
On 4WD tractors, all of the weight of the tractor is always on the driving wheels. Therefore, these tractors can and should be loaded with the maximum front axle weight specified by the manufacturer.