The Purdue Univ. soil-vehicle laboratory located in the Agricultural Engineering Building was used to study the effect of dual, single, and tandem drives on artificial soils. The dual versus single tire comparisons were made with 4.00 × 8 tires. Two tandem drive combinations were used. The first combination utilized 4.00 × 8 tires for both the front and rear wheels, and the second combination used a 4.00 × 8 tire for the front wheel and a 6.00 × 12 tire for the rear wheel.
Dual tires performed better than single wheels of the same weight when tested on loose soils. The full advantage of dual tires was not obtained without lowering the inflation pressure below that of a single tire of the same weight.
A weight distribution of 60% of the total weight on the front wheel produced better performance for the tandem drive using equal size tires than did the weight distribution of 50% or 40% on the front wheel. The performance at a tire pressure of 6 psi was superior to that at 9 and 12 psi.
The performance of the tandem drive using the smaller front wheel was nearly equal for all weight distributions at higher tire pressures. However, at a tire pressure of 6 psi the weight distribution with 25% of the weight on the front wheel proved to have a higher tractive coefficient than either of the other two weight distributions of 35 or 45% on the front wheels.