>>2729783As
>>2729788 said, optimal ballasting improves traction while minimizing slip, which saves fuel and allows you to work faster. Filling tires with water used to be quite popular in the past. The issue with water is that it's a pain to put in and get out and that it does little to improve the footprint of the tire. These days it's preferred to use wheel weights that go in the rim while also reducing tire pressure to around 0.8 bar. This also increases the footprint of the tire thus improving traction even further.