3. Add air, if necessary: 127 Tire Size Ply Rating Pressure 16 x 6.50 - 8 4 40-193 kPa (6-28 psi) 16 x 7.50 - 8 2 56-83 kPa (8-12 psi) 18 x 8.50 - 8 4 40-152 kPa (6-22 psi) 23 x 8.50 -12 2 40-70 kPa (6-10 psi) 23 x 10.50 -12 2 40-70 kPa (6-10 psi) 26 x 12.00 -12 2 40-70 kPa (6-10 psi) 26 x 12.00 -12 4 40-138 kPa (6-20 psi)