shimming of main gear

[givo]

Dear all , I'm new in this forum so excuse me if I ask some already answered question or if I?m posting in the wrong area . I have an RV-7 and some time taxing I notice a shimming , a vibration forward and aft of the legs of the main gear , especially when I have to vacate quickly so I need some speed . I have noticed that this happens when I inflate tires at 2,0 - 2,5 bar ( 30 - 40 psi ) ,but if I inflate at 1,6 bar ( 24 psi ) this does not happen ..... can that be true or the pressure of tire does not influence this behavior , is something else ? thanks for answering . Giulio

[RV3bpilot]

This subject has been on going. I have a shaking wheel and have done almost everything one can do to stop it.
I have made my own gear leg stiffeners
I balanced the wheels
changed tires
adjusted the pressures

The thing that helped the most was the gear leg stiffeners.
The second best was changing brand of tires. I'm not going to specify tire brands because some have luck with one brand and others with another.

Without gear leg stiffeners on my first taxi test it shook so hard I thought the gear leg might separate from the fuselage! Then I made the stiffeners per Van's manual and all the shaking went away. But when I turned the tires around so I could wear them evenly, they wear more on the outsides, (normal wear), then I had a mild shake come back in the left leg.
I tried a different brand of tire and it was worse!
I still have a tire shake on the gear left leg but it is mild and only last a few seconds as I slow down.

I made my own tire balancing jig and that did help some. The tire shake on almost every RV seems to be at about 15 to 20 mph.
Type in gear leg shake in the search bar and you will find what others have done.

Good luck

[Bevan]

Gear shimmy was non-existent for the first hundred hours or so and then I started to get a shake around 20-25kts taxi speed. Balancing and changing tires did not make a difference. It turns out my tire gauge was becoming faulty and the actual tire pressure was too high. I bought a very good pressure gauge and started playing with the pressures using a video camera mounted under the fuselage. I've found 25-30lbs to be ideal for the mains, and 35 for the nose wheel.

Bevan

[givo]

Originally Posted by Bevan

Gear shimmy was non-existent for the first hundred hours or so and then I started to get a shake around 20-25kts taxi speed. Balancing and changing tires did not make a difference. It turns out my tire gauge was becoming faulty and the actual tire pressure was too high. I bought a very good pressure gauge and started playing with the pressures using a video camera mounted under the fuselage. I've found 25-30lbs to be ideal for the mains, and 35 for the nose wheel.

Bevan

Dear Bevan thank for the info , could you please specify the pressure units ? .... 25-30 is in psi I guess ? in atm should be 1,7 - 2,0 is that correct ? thanks Giulio

[givo]

I have changed the brake disks and I have installed new tire . The problem of shimming has almost disappeared ....