We recommend that the tire pressures be checked before doing any other adjustments, as this may be the problem and any further adjustments would also require the tires be properly inflated beforehand.

Tire pressures are stated in Pounds per Square Inch (PSI) measure. The factory settings for residential riding mower tires are generally 10 PSI for rear tires and 14 PSI for front tires. But it's a good idea to always check the side wall of the tire itself, as the tires on a particular model may not always be standard equipment tires. The maximum tire pressure is embossed on each tire. This is the maximum tire pressure. Inflating tires to 2-3 PSI under the maximum is also acceptable. as long as the pressure in both front tires are the same and both rear tires are the same.

If this doesn't solve the problem, a deck leveling adjustment may be needed. The deck leveling adjustment varies by model and is explained in the Adjustments section of the Operator's Manual. Please refer to the Operator's Manual and follow these instructions as they relate to the particular tractor being serviced.

If the above actions do not correct the problem, it may also be one of two other situations:

1. The blades and/or spindles could be worn or out of balance. 
2. There may be bent or damaged deck hangers that would require replacement.

If further assistance is needed, please visit a local authorized service center and have them visually inspect and service the mower.