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  #1  
Old 09-16-2019, 05:42 PM
Strappe Strappe is offline
 
Join Date: Jul 2017
Location: Omaha, NE
Posts: 17
Default Shudder after takeoff

About the time our 2015 RV-12 leaves the ground on take off I feel a distinct shudder. I think that pressing on the brakes stops it, but not instantly, which makes me wonder if it just goes away spontaneously. At the time of this year's annual condition inspection, I replaced the brake rotors, pads and installed new tires (but not new tubes). The tires had significant asymmetric wear, and rather than just switch them R to L (which requires un-mounting the tires), I put on new tires.

On takeoff for the post-inspection and maintenance test flight, the shudder was still there. I'm wondering if the next step is to balance the wheels/tires?
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  #2  
Old 09-16-2019, 06:05 PM
Piper J3's Avatar
Piper J3 Piper J3 is offline
 
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Location: Hinckley, Ohio
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Might be nose wheel out of balance. Stick-on lead weights fit nicely inside wheel hub.
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Jim Stricker
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EAA #499867
PPL/ASEL 1970 - Sport Pilot since 2007
80 hrs Flying Aeronca Chief 11AC N86203
1130 hrs Flying 46 Piper J-3 Cub N6841H
RV-12 E-LSA #120058 AWC July 2012 N633CM
RV-12 Bought Flying Oct 2015 with 48TT - Hobbs now 510

LSRM-A Certificate 2016
Special Thanks... EJ Trucks - USN Crew Chief A-4 Skyhawk
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  #3  
Old 09-16-2019, 06:18 PM
mflander4 mflander4 is offline
 
Join Date: Jul 2019
Location: Elk River, MN
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If the brakes don’t stop it I would assume nose wheel also. Balancing would be the fix. I’ve researched a bunch and can’t remember what thread but I’m certain I’ve read about a nosewheel shimmy on the 12 a couple times...

Reason for my post though is to ask if the asymmetric wear on the tires is considered normal or should something be adjusted for that?
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  #4  
Old 09-17-2019, 01:04 AM
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Piper J3 Piper J3 is offline
 
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Quote:
Originally Posted by mflander4 View Post
Reason for my post though is to ask if the asymmetric wear on the tires is considered normal or should something be adjusted for that?
Perfectly normal. Outside edges wear because unloaded gear will change camber angle and as airplane touches down for landing the outside edge of tire makes contact with the runway first.
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Jim Stricker
Hinckley, Ohio (1OA2)
EAA #499867
PPL/ASEL 1970 - Sport Pilot since 2007
80 hrs Flying Aeronca Chief 11AC N86203
1130 hrs Flying 46 Piper J-3 Cub N6841H
RV-12 E-LSA #120058 AWC July 2012 N633CM
RV-12 Bought Flying Oct 2015 with 48TT - Hobbs now 510

LSRM-A Certificate 2016
Special Thanks... EJ Trucks - USN Crew Chief A-4 Skyhawk
MJ Stricker (Father & CFI) - USAAF 1st Lt. Captain B-17H
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  #5  
Old 09-17-2019, 07:31 AM
Strappe Strappe is offline
 
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Location: Omaha, NE
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Thanks all. Nose wheel is a good bet.
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  #6  
Old 09-18-2019, 05:54 AM
dwmillsap dwmillsap is offline
 
Join Date: Jul 2010
Location: Winterville NC
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Tap your brakes when it shudders. If it stops, then it's your mains that are out of balance. You can even tap one side or the other to find out exactly which wheel is misbehaving.
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  #7  
Old 09-18-2019, 10:51 AM
mturnerb mturnerb is offline
 
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Location: Ponte Vedra, FL
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I had the same problem on my RV-12. Balanced nosewheel, fixed the issue. I ordered a motorcycle wheel balancer - worked perfectly.
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  #8  
Old 09-19-2019, 07:40 PM
RFSchaller RFSchaller is offline
 
Join Date: Oct 2010
Location: Phoenix, AZ
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Like Turner said. Once I balanced my nosewheel my shudder went away. I got over 500 hrs on my first set of tires and wear was pretty even which really surprised me given the way the plane sits on its gear.
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