How do you know if they need replacement?

Get on your hands and knees under the wing and use your back to lift the wing. Observe the tire. If it drops any, (about an inch or more), the donuts are compressed and probably need replacement.

How bad is bad?

Worn or compressed donuts will allow the wheel and tire to chatter in the wheel well during flight, from engine vibrations. This will cause unnecessary wear on the linkage bushings. If the donuts are severely compressed, the tire could contact the wing cut-out for the gear.

Most retractable gear airplanes have 'Jack pads', or some call them 'Jack Points', to raise the plane for the retraction test. The Mites don't have them, so the usual procedure is to use a standard auto hydraulic jack at the landing gear to raise the wings enough to place padded sawhorses under them, near and outboard of the landing gear, with a weight on the tail or rear part of the fuselage.

Upon reading the above, Boyd Maddox, N352A, sent in the following comments: "The original factory service bulletin also shows the tail being weighted. But I have a problem with holding the tail of ANY Mooney down. Use a prop stand or engine hoist and lift the front of the airplane. This is the procedure suggested by Mooney even today."

How to install new donuts:

1. Remove the lower part of the gear. Three bolts will have to be removed. 

2. Use an electric drill to drill a pilot hole at the bottom of the frame that holds the donuts. This hole should just be deep enough, so that it will hold the point of a wheel puller center bolt in position. 

3. Install a standard wheel puller, so that when you crank the tension on the wheel puller bolt, it will compress the donuts. Compressing the donuts sufficiently will allow you to...
4. Remove the bolt holding the center spindle that goes through the donuts.

5. Install the new donuts, reversing the procedure. 

CAUTION -- Wear some kind of eye protection, because if the wheel puller should let go, it will do it with a bang, like a shotgun. 

Normally the donuts should last ten years of regular flying. They are still available, although a little expensive. The Mite donuts are the same ones used on the Mooney Mark 20 early models. 

Submitted by Ben Favrholdt, N66MX