Determining Ballasted Tractor Weight, Weight Split, Axle Loads and Required Tire Inflation Pressures

The Unballasted Tractor Weight Charts provides front axle, rear axle and total weights for all power train and tire size options. Considering this and the information previously provided on weights of various ballast elements (QUIK-TATCH weights and wheel weights), front ballast multipliers and front hitch axle loads (if used), the ballasted tractor weight and axle loads can be calculated. These are needed to determine if total weight and weight split recommendations are met and to look up required tire inflation pressures from Recommended Pressure Charts in Wheels, Tires, and Treads section.

Example 1

So the tractor is ballasted to the level of 11378 kg (25083 lb) / 200 PTO-HP = 56.9 kg (125 lb) per PTO-HP (Medium).

The percentage of weight on the front axle is 4784 kg / 11378 kg (10546 lb / 25083 lb) x 100% = 42%.

From the Table of Recommended Inflation Pressures in Wheels, Tires, Treads (section 80) for calculated axle loads, the required inflation pressures are:

Front Inflation Pressure 140 kPa (1.4 bar; 21 psi)

Rear Inflation Pressure 60 kPa (0.6 bar; 9 psi) but only if tractor is towing an implement that places very little load on drawbar (planter or air seeder).

For implements that generate high weight transfer add approximately 50 kPa (0.5 bar; 7 psi) for a total of 110 kPa (1.1 bar; 16 psi) for rear tires. With the aid of an assistant, visually check tire deflection when tractor is pulling hard in the field to confirm that tires are not under-inflated with these pressures.

For trailers, tankers, or any heavy integral implement the rear inflation pressures MUST be increased substantially to support the extra weight at transport speeds. The exact amount depends on the extra load. Usually it will be MORE THAN DOUBLE the base amount or 130 - 150 kPa (1.3 - 1.5 bar; 19 - 22 psi) for this example. To determine rear axle load exactly, weigh rear axle of loaded tractor on a platform scale.

Example 2

So the tractor is ballasted to the level of 12351 kg (27231 lb) / 225 = 55 kg (121 lb) per PTO-HP (Medium).

The percentage of weight on the front axle is 4438 kg (9783 lb) / 12351 kg (27231 lb) x 100% = 36%

From the Table of Recommended Inflation Pressures in Wheels, Tires, and Treads for the calculated axle loads, the required inflation pressures are:

Front Inflation Pressure 120 kPa (1.2 bar; 18 psi)

Rear Inflation Pressure 80 kPa (0.8 bar; 12 psi) but only if the tractor is towing an implement that places very small load on the drawbar (planter or air seeder).

This is the ideal configuration for a 8270R MFWD tractor when it is used with towed implements such as planters or air seeders. The front weight percentage should be approximately 35% or less to help prevent power hop. Although this tractor is slightly over 35%, it is close enough. Power hop can still occur, but it can be controlled using the procedures given in this section of the manual. If the percentage is much higher, control may not be possible.

When this tractor is used to tow large trailers, the rear inflation pressure must be increased as outlined in Example 1.

If this tractor is used with heavy integral or semi-integral implements, additional front ballast and higher rear inflation pressures will be required.