Weight matters, but placement matters more.
From wheel weights and front weights to underbelly and rear weights, there are many ways to balance a tractor. But the real question is: Where is the right place to put the weight?
Getting the right balance
A typical guideline is a 60/40 weight distribution between rear and front axles. Too much weight on the front is a common issue, leading to reduced traction and unnecessary stress on the axle. Rear weights often provide better stability when carrying front-end loads, whilst wheel weights improve grip directly at the tyres – power goes where the weight is. Underbelly weights lower the centre of gravity and spread loads more evenly, especially on slopes.
It is important to consider weight on the rear axle with rear implement lifted, and front axle when the rear implement is in work. Similarly, consider front axle when the front implement is lifted. Common scenarios where over loading occurs are:
- Fertiliser spreading: rear axle when spreader is full, front axle when spreader is empty
- Drilling and cultivations: front axle when implement is in work, rear axle when rear implement is raised
- Grain trailers: Front axle when trailer is empty
Weight and horsepower
The relationship between weight and horsepower is also critical. Depending on the work, machines perform best at:
- 35kg per horsepower for transport, such as pulling trailers
- 45kg for light cultivation and low draft activities
- 55kg per horsepower for high draft work such as subsoiling or ploughing
Too little weight leads to slippage, whilst too much increases fuel use and risks overloading axles. As a rule of thumb, 1000kg of additional unrequired ballast can use an extra litre of fuel per hour.
Tyre pressure and axle load
Weight placement is crucial, but is only part of the picture. Tyre pressure and axle load both have significant influence, particularly when it comes to soil health. Topsoil compaction is driven mainly by tyre pressure, whilst subsoil compaction is caused by axle load. Exceeding safe limits in either case can result in lasting damage to the soil structure. As machine sizes increase, we are seeing irreparable damage to subsoil and it is crucial that axle loads are no larger than necessary. Where the level of weight required is higher than desired, a competent wheel specialist such as Brocks Wheel and Tyre will advise on the best product available to mitigate damage.
How to get the ballast right
Getting ballast correct comes down to balance. A few key takeaways:
- Aim for a 60/40 split between rear and front axles
- Match the total weight to the horsepower (35kg per hp for transport up to 55 kg per hp for draft work), and avoid adding unnecessary mass that increases fuel use and overloads axles.
- Use the right combination of rear, front, wheel and underbelly weights to keep the tractor stable.
- Adjust tyre pressure and watch axle loads to protect both the topsoil and subsoil.
When each factor is considered together, the tractor runs as intended and the soil health is preserved.
