No. 6. DEPARTMENT OF AGRICULTURE. 987 



Contrary to general expectations the broad tire pulled the lighter 

 on the hard, inelastic, smooth surface of the rock road. 



In these trials there was a dilference in draft in favor of the broad 

 tires amounting to 20 pounds or oo.7 per cent, in one trial and 20.1 

 pounds, or 10.8 per cent, in another, or an average of 21 pounds, or 

 20 per cent., the trials being almost a month apart. In other words, 

 with the draft required to draw 2,000 pounds over this road on nar- 

 row tired wheels a load of 2,714 pounds could have been hauled 

 on the broad tires in one trial, and 2,322 pounds in the second trial, 

 or 2,518 pounds as an average of both trials. 



II. Gravel Road. 



(a) Hard surface, no ruts, some loose stones size of black walnuts. 

 Trial made October 12, 1890. Length of run, 400 feet. 



Average draft. 



Narrow tires, 218.4 pounds. 



Broad tires, 103.8 



Difference in favor of broad tires, 54.0 " 



Percentage difference, 33.3 " 



(b) Dry, hard and free from dust. A few loose stones lying on the 

 surface. Length of run, 400 feet. Trial made November 20, 1896. 



Average draft. 



Narrow tires, 145.7 pounds. 



Broad tires, 100.2 



Difference in favor of broad tires, 45.5 " 



Percentage difference, 45.4 " 



(c) A large quantity of sand in the gravel which prevented it from 

 packing perfectly. Eoad dry and free from ruts. Run made August 

 29, 1890. Length of run, 400 feet. 



Average draft. 



Narrow tires, 239 . 1 pounds. 



Broad tires, 150.7 " 



Difference in favor of broad tire, 72.4 " 



Percentage difference in favor of broad 



tire, 45.5 " 



(d) New. Before the gravel had become compacted, reasonably 

 dry and firm. No ruts. Length of run, 400 feet. March 20, 1897. 



Average draft. 



Narrow tire 329 .9 pounds. 



Broad tire, 200.5 « 



Difference in favor of broad tire 09.4 " 



Percentage difference in favor of broad 

 tire 20.6 " 



(e) Water standing on surface. Loose sand varied in depth from 



