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Old 03-25-2018, 07:52 PM
TKoehn TKoehn is offline
Join Date: Mar 2018
Location: Boise, ID
Posts: 3
Default Shimmy

Hello All

I hate to bring up an old subject that has been discussed in length already. But I have been fighting some leg shimmy for a while now on my -6. I have, and have tried the following:
-No gear stiffeners(removed them after I repaired motor mount cracks)
-Flight Custom 3, 6ply tires
-Psi from 25 up to 50(much worse with high pressure)
-Tires new in 2015 with 200hrs
-Recently rotated on the rims(shimmy before and after)

Now my question. While balancing them the other day I noticed that they were significantly out of round. And required a lot of weight on one tire. The flat spots seemed to be the side that had been sitting on the ground for the past couple days. Is this a normal out of round condition? Will new tires also flat spot as these do when they sit for a couple of days? Or does this warrant replacement? They have a fair amount of life left on them and would hate to throw away expensive tires. I appreciate any opinions.

Last edited by TKoehn : 03-25-2018 at 07:58 PM. Reason: Add information
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Old 03-25-2018, 08:38 PM
Bob Martin's Avatar
Bob Martin Bob Martin is offline
Join Date: Jan 2005
Location: Richmond, Virginia
Posts: 1,114

WE use 40 psi. Good compromise between high and low.
Low will lead to flats!
Yes the tires will get flat spots from sitting and take a little taxing to smooth out. Seems like you should take the wheel assembly off the plane and let it round out before balancing.
Some tires need lots of weight to balance.
Good luck.
Bob Martin
RV-6, 0-360 Hartzell C/S, Tip up, 1150+TT
James extended cowl/plenum, induction, -8VS and Rudder. TSFlightline hoses. Oregon Aero leather seats.
D100-KMD150-660-TT ADI2- AS air/oil seperator. Vetterman exhaust with turndown tips.
Louisa, Virginia KLKU N94TB
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Old 03-25-2018, 09:48 PM
TKoehn TKoehn is offline
Join Date: Mar 2018
Location: Boise, ID
Posts: 3

Thanks for the psi recommendation but I have tried the 40 psi range. Anything above 30psi makes the shimmy much worse. Maybe I should pull the wheels and let the tires (round out) for a while and then try to balance again.
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Old 03-25-2018, 10:04 PM
rockwoodrv9 rockwoodrv9 is offline
Join Date: Dec 2011
Location: Meridian ID, Aspen CO
Posts: 2,461

I sent you a PM. I am at KEUL.
Meridian Idaho
O-320 D2A
Awaiting DAR Inspection
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Old 03-25-2018, 10:48 PM
Tracer 10 Tracer 10 is offline
Join Date: Mar 2011
Location: Oregon
Posts: 89
Default Shimmy

1. Check the bolts that hold the axel to the gear leg for proper torque. They will loosen over the years and may need new hardware.
2. Check for play where the gear leg slips into engine mount.
3. Check bolt & nut for proper torque where gear leg is bolted to engine mount.
CW4 (Retired) U.S. Army
A&P: I pay double dues (it's worth it)
Oregon RV-6
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Old 03-25-2018, 11:35 PM
TKoehn TKoehn is offline
Join Date: Mar 2018
Location: Boise, ID
Posts: 3

I just reamed the gear leg mounting bolts up to an oversized NAS to remove the play I had there. But I have not checked the axle mounting bolts. Thatís a great idea that I have overlooked. I will check that too. Thanks
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