Post Oshkosh Maintenance

Last winter I noticed that the center of my nose gear tire was getting scuffed. It turned out that my gear leg extended a bit too far past the nut and would scrape it during landings. I called the factory and was told to file the aft side of the gear leg until I got 1/4 inch clearance to the tire. I did that and the scraping stopped. I decided to replace the tire anyway, as much for looks as anything else. I bought the tire, but put off doing the work until recently when a little pre- Oshkosh incident brought it back to my attention.


I went out to the airport the day before Oshkosh to do a little pattern work. I took off, remained in the pattern and came in to do a touch and go. Since I was staying in the pattern, I left the gear down.

When the nose gear contacted the runway after touchdown, the airplane shuddered violently and noisily. I knew from descriptions I'd heard that this must be the dreaded nose gear shimmy. I applied full power, lifted the nose and went around.

I came back around and slowed as much as I could on final. I landed on the mains and then balanced braking and increasing amounts of back pressure on the stick to keep the nose wheel off the ground as long as possible. When it finally came down, I got a bad shimmy again, but slowed quickly to the point where it just stopped.

I taxied back to the hangar and felt the side force on the gear. It felt a little light, but not much. I tightened the nut on the nose gear until the nose gear was pretty stiff and took about 20 pounds of force on the back of the wheel to turn. This involved tightening the nut only about a quarter turn.

I taxied back out and did another pattern, this time putting the gear up and extending it again mid-field. The shimmy was completely gone.

In retrospect, I think the incident had a combination of causes. First, I likely let the nut get a bit loose. Second, I was probably a bit out of practice and let the nose gear come down less gently than usual. Third, I landed without retracting the gear in flight.


Normally, I will get a quick smell of rubber when I retract the gear from the nose wheel spinning against the safety guides in the nose. Gyroscopic precession can make the wheel turn slightly as it spins down. The guides straighten it out as it is retracted. I'll bet the nose wheel was slightly turned when I touched down, causing the shimmy.

Now the tire was scuffed on the sidewalls too. I decided to finally put on that new tire I'd had sitting in my hangar. I tried and tried to get the axle out but could only get it part way out before it would jam. If you click on the above picture, you'll see that I got it part way out and then buggered up the slot in the axle.

I found out from the factory that it is not uncommon to have the mild steel axle bend ever so slightly so that it can't be turned out. The fix is to cut out the old one with an air body saw and replace it with a new axle. I ordered a new axle and nut and went flying while waiting for them.

As I was taxiing, I noticed a clicking or grinding noise from the nose gear. The shimmy had been the final straw for the nose wheel bearings, so I decided to replace them as well, since a new set was only $29.

I decided I'd post a few pictures of the nose gear rehab for the benefit of anyone who has yet to do it.

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First step, I got the wheel removed and down to my work shop. You can see the wear from the gear leg on the tire.

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Here is a shot of the new bearings, new axle and new lock nut. The tool at the upper left is a ratcheting allen wrench- very handy for taking the wheel apart. The lower left is a valve stem tool.

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Here's a close up of the valve stem tool. It's best to remove the valve stem before disassembling the wheel.

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Using the air body saw to cut the axle between the spacer and the fork. This actually took only about 10 minutes. I used a clamp to squeeze the tire out of the way.
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Next step, take the wheel apart, pull out the innertube and install them on the new tire. Make sure the valve stem goes next to the red dot painted on the tire which marks the light spot on the tire.
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I couldn't help myself. While it was disassembled, I polished and buffed the fork to a nice shine and polished the wheel. Compare this shot with the first picture in this post for the before and after. Also, note the new bearing sitting on the tire, freshly packed with grease and ready to install.

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Here it is, all rebuilt and ready to reinstall. Now you can see the red dot for the light spot.
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I had been using a huge Channel Lock pliers to install and tighten the nose gear nut. An internet search turned up this 1 15/16 combination wrench for only $18. It worked great.

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You may recall from my Oshkosh post that Carlos from GRT Avionics had pointed out that the display on my TruTrak autopilot was failing. I sent it back to them and they fixed it in 48 hours at no charge. I was impressed. I got it back just in time to get everything reinstalled at once.

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I got out to the hangar to find that Hurricane Irene had blown a tree over at the airport and knocked out power to the airport. No lights, no opening the hangar door. I lined up some flashlights and got it installed any way.

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Reinstalling the autopilot in the dark was even more fun. I got it done and the only thing left to do is inflate the nose tire. Again, no power, so the inflator won't work tonite.

I'll fill the tire and test fly this Friday so that we are good to go for Ocean City for the holiday weekend.
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If you are at the New Jersey shore on  Saturday, keep an eye out for a Velocity cruising down the beach!

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