SOIL STRESS AND COMPACTION EFFECTS FOR 4 TRACTOR TIRES

Compaction effects and soil stresses were examined for four tractor ty res under three inflation pressures: 67, 100 and 150% of the recommend ed pressure. The four tyres were 18.4 R 38, 520/70 R 38, 600/65 R 38 a nd 650/60-38 and they carried a wheel load of 2590kg. The 650/60-38 wa s a bias-ply tyre while the other three were radial tyres. Increased i nflation pressure significantly increased all measured parameters: rut depth, penetration resistance and soil stress at 20 and 40 cm depth. The 18.4 R 38 caused a greater rut depth and penetration resistance th an the other tyres, which did not differ significantly from each other . The soil stress was highest for the 18.4 R 38, followed by the 650/6 0-38.The low-profile tyres decreased compaction compared with the 18.4 -38 tyre, mainly by allowing a lower inflation pressure. The use of lo w-profile tyres did not reduce compaction if not used at a lower infla tion pressure. The bias-ply tyre caused a higher stress in the soil th an the radial tyres when used with the same inflation pressure, but th e compaction effects in terms of rut depth and penetration resistance were not greater for this tyre than for the radial low-profile tyres. (C) 1997 published by Elsevier Science Ltd on behalf of ISTVS.