Ko. 6. DEPARTMENT OF AGRICULTURE. 1003 



public expectation, in a large majority of cases the draft was ma- 

 terially less when tires six inches in width were used than when the 

 tests were made with tires of standard width, 1^ inches. The follow- 

 ing is a summary of the results: 



I. On macadam street, as an average of the two trials made, a 

 load of 2,518 pounds could have been hauled on the broad tires with 

 the same draft that a load of 2,000 pounds required on the narrow 

 tires. 



II. Gravel road. In all conditions of the gravel road, except wet 

 and sloppy on top, the draft of the broad tired wagon was very much 

 less than that of the narrow tired wagon. Averaging the six trials, 

 a load of 2,482 pounds could be hauled on the broad tires with the 

 same draft required for a load of 2,000 pounds on the narrow tires. 



III. Dirt roads, (a) When dry, hard, and free from ruts and 

 dust, 2,530 pounds could have been hauled on the broad tires with 

 the same draft required for 2,000 pounds on the narrow tires, 

 (b.) When the surface was covered with two or three inches of very 

 dry, loose dust, the results were unfavorable to the broad tires. The 

 dust on the road in each of these trials was unusually deep, (c.) On 

 clay road, muddy and sticky on the surface and firm underneath, 

 the results were uniformly unfavorable to the broad tires, (d.) On 

 clay road, with mud deep, and drying on top, or dry on top and 

 spongy underneath. A large number of tests showed uniformly 

 favorable to the broad tire. The difference amounted to from 52 

 to Gl per cent., or about 3,200 pounds could have been hauled on the 

 broad tires with the same draft required to draw 2,000 pounds on 

 the narrow tires. In this condition of road the broad tires show 

 to their greatest advantage. As the road dries and becomes firmer, 

 the difference between the draft of the broad and narrow tires 

 gradually diminishes until it reaches about 25 to 30 per cent, on dry, 

 hard smooth dirt, gravel or macadam road, in favor of the broad 

 tire. On the other hand, as the mud becomes softer and deeper, the 

 difference between the draft of the two tj'pes of wagons rapidly 

 diminishes until the condition is reached when the mud adheres to 

 both sets of wheels; here the advantage of the broad tire ceases 

 entirely, and the narrow tires pull materially lighter, (e.) Clay road, 

 surface dry, with deep ruts cut by the narrow tires in the ordinary 

 use of the road. In every trial the first run of the broad tire over 

 the narrow tire ruts has shown a materially increased draft when 

 compared with that of the narrow tire run in its own rut. The 

 second run of the broad tires in the same track where the rut is 

 not deep completely eliminated this disadvantage, and showed a 

 lighter draft for the broad tire than the narrow tire show^ed in the 

 first run. Where the ruts were eight inches deep with rigid walls, 

 three runs of the broad tires in its own track over the ruts were 



