Zero Turning Radius (zero turning radius) riding mowers (Figure 1) can do a wonderful job of maintaining turf, but the rapid response and maneuverability that make them so handy can cause problems if you aren’t careful.
Zero Turning Radius mowers allow you stop, turn or reverse direction almost instantly by rapidly moving the steering levers. Sometimes the momentum or inertia of the mower resists rapid changes in speed and/or direction, causing the drive wheel(s) to slide or spin. This is an especially common problem on wet turf, but it can (and does) happen on dry grass also. It is a serious safety problem when mowing on hillsides.
This slippage has several detrimental effects. First, it causes a loss of control. If the mower is sliding or spinning, you are not in control of the vehicle motion. It is easy to run into a tree or other obstacle when the mower slides. Second, wheel slippage may cause severe turf damage. A rapid start, stop or turn can strip the turf from a square foot or more, leaving the soil bare for months until the turf recovers (Figure 2).
A more serious problem is side slippage on slopes. If operated on a slope, the mower may slide all the way down the slope before it stops. If there is a ditch, pond, creek or dropoff of any kind at the bottom of the slope, the mower can overturn. Most Zero Turning Radius overturns are the result of sliding. It can also slam into a wall, fence, tree or anything else that happens to be at the bottom of the slope. Ideally, you should back up a slope and drive down rather than driving across the slope, but that recommendation is not always possible to follow. In fact, tire slippage may make it impossible to back up a slope with a Zero Turning Radius mower. If you do have to drive around a contour on a slope, you may notice the rear tires slipping downhill slightly, causing the mower to run at a slight angle to the direction of travel (called “yaw”).
The best advice for avoiding these problems is to move the steering levers smoothly and slowly. It is also important to have a rollover protective structure (ROPS) on your mower.
Just because you have the capability of spinning the mower around its center or stopping on a dime doesn’t mean it is wise to do it often. You should avoid pivot turns -- you will cause much less turf damage if you keep both drive tires rotating while you turn. You can make short turns without slippage or turf damage if you just decelerate gradually before the turn, then turn slowly and accelerate gently. With a little practice, you will learn how gently you have to drive your mower under different turf conditions. Avoiding wet turf certainly helps minimize slippage problems.
If you encounter slide slippage or yaw on a slope, you will have to speed up the lower drive wheel and slow the upper wheel, thus allowing the mower to run with the amount of yaw angle necessary to maintain your travel across the slope.
In summary, fully using the quick-maneuvering capabilities of your Zero Turning Radius mower can damage turf, cause you to run into fixed objects or cause you to slide all the way down a slope. A gentle touch on the steering levers will do the job just as fast but with minimal slippage and damage.