Rear tire pressure.

in a post below Bill from Scotland asked about tire pressure. Some said they run as little as 5lbs of pressure. I thought that was incredibly low, especially for a 150 hp+ tractor. When I had my 1370 I had to run about 20 lbs in the tires to keep the sidewalls from buckling and causing chattering and jumping. I'm wondering what all of you run in your tires?

On the 1256 with 18.4x38 (8ply),18 lbs.The other tractors are similar.However,in 'tractor pulling',we often let the air down to 3-5 lbs.

For radials on tillage tractors we run about 13-14 psi. Yard tractors with bias tires usually go 16-18. Several years ago I visited the Dakota Lakes Research Farm by Pierre, and they had oversize radials on tractors running around 6 psi to minimize compaction.

Depends on radial or bias, and axle loads.
Generally, for bias, take the width in inches and add 2. For example, 14 psi in 12.4's, 18 psi in 16.9's or 20 psi in 18.4's.

rear tire pressure is determined by how the tire sets on the ground. park in a spot where the tire is on a hard surface. now lower the pressure till the tire sets flat on the surface. check pressure to see where you are at, every tire will be different. it depends on size composition and weight of tractor.
Walt

"Loaded Tires" require much less pressure to be properly inflated...

Ron..

On our JD 4960 we run 8-10 PSI on the rears when pulling the finisher in the spring. They are Firestone 20.8 x 42 radials. This pressure is within the design for weight and load. It really makes a difference in the surface compaction.

When I originally weighted this tractor we took it to the local grain elevator and weight the front and back axles. Then the total tractor. Then I played with front and rear wheel weights to get where is should be.

Here is how the numbers turned out. I wanted 115 lbs. per horse power for total weight. So 200 x 115 = 23000. Then I wanted the final weight to be 60% rear and 40% front. So that worked out to be 13800 lbs on the rear and then 9200 lbs on the fronts. Then I looked up the rated weight carrying capacity at 6-8 MPH on the rear tires. This is divided by four when we run the duals and two when we are not. That worked out to be 8 PSI with the duals and 18 PSI without.

The fronts tires at full ballast weight require 20 PSI. When we remove the duals we also remove most of the front weights. We then run the front tires at 15 PSI. It makes the tractor ride much better. I am considering front duals for tillage but at $6500 for them I am not jumping right now. We have been thinking about getting a full 4wd for heavy tillage.

I think that's why some guys get such a harsh ride when they load their tires.

Everyone here wants to run everything at sidewall max pressure. I lowered the rears on the 4840 to 18 inside and 15 outside (18.4-42), fronts to 30 from 45, and didn't bounce out of the seat planting.

Had to find some balance between carrying a 16 row planter down the road and ride quality in the field.

For real Field-Work, I always felt that loaded tires give a better foot-print (traction)..than an equal amount of weight added to the wheel or tractor..
The more a tire is filled with fluid, the less air volume is available to compress (cushion) when the tire hits anything..but, a loaded wheel always needs far less pressure than one that is not loaded..

Ron..