The experience of Iowa farm users of 199 sets of pneumatic tractor tires indicates satisfactory durability and field performance. These users, selected as a representative sample, were located in 73 counties and represent the equivalent of 381 years of individual observation.
McKibben, Eugene G. and Davidson, J. Brownlee
"Life, service and cost of service of pneumatic tractor tires,"
Bulletin: Vol. 34
, Article 1.
Available at: https://lib.dr.iastate.edu/bulletin/vol34/iss382/1