Avoid extreme pull forces on the Pivot pad

Categories: Operation and Maintenance

shims behind the gearbox mounting bolts

The following is recommended for (usually long) machines that are creating extreme pull forces on the Pivot pad. It may also be necessary if pad is located on the high point in field. Under normal conditions, the gearboxes should be perpendicular to the base beam.

Wheel adjustment procedure

At each drive unit, stretch a string across both tires and measure or estimate the “d” dimension at the point where the string is closest to touching the tire. If the string contacts the outer part of the tire before the inner part, the tire is toed out. We want the tires to be toed in, so the string contacts the inner part of the tire.

Install shims behind the gearbox mounting bolts to adjust the toe-in of the tire. Always shim both the top and the bottom bolts equally whether shimming the outside or the inside. You will also want to shim the bottom center bolt hole (with smaller shim) to prevent uneven stresses on the back of the gearbox when all bolts are tight. We don’t want to adjust the wheel in or out from top to bottom, only from side to side. Shims are available in 0.03″ 0.06″ and 0.12″ thicknesses.

a string across both tires: pivot drive unit

For a 14.9 x 24 tire, each 0.06″ of shim will change the tire toe-in by about 0.375″. On the first drive unit, the bolts should be changed to 1/2″ x 1 1/2″ since so much shim thickness is required.

After shimming, remeasure the toe-in and keep adjusting until both wheels are approximately the same on a given drive unit and both are as close as possible to the recommended “d” dimension.

On the inner towers, get as close to the recommended dimension as possible with the shims available. It’s not necessary to be exact. On drive units more than 1,800″ from the pivot point, try to adjust the tires so the “d” dimension measures 0.0″ – 12″. Under no circumstances should any of the tires be toed out away from the pivot point.

Length to drive unit (feet) “d” Dimension (inches)
150 1.55
300 0.78
450 0.52
600 0.39
750 0.31
900 0.26
1200 0.19
1500 0.16
1800 0.13
>1800 0-0.12

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