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  #1  
Old 09-11-2006, 12:30 PM
Paul Eastham's Avatar
Paul Eastham Paul Eastham is offline
 
Join Date: Oct 2005
Posts: 509
Default Flat spots on tires?

Hey everyone,
When I give my main wheels a spin, there seems to be a flat spot on each tire, perhaps 1/8" out of round. It's not huge, but definitely noticable if you spin the wheel and look at the tire from above.

The fuselage has been on the gear for over a year, but I feel like I have moved it at least every 3 months, hopefully causing a different spot to be on the ground. I have made it a point to not park on the flat spots recently, but the problem is not going away. Tire pressures have been to spec throughout this time, and the overall condition of the rubber looks good to me. I have not flown or taxied the airplane yet.

Should I look into new tires, already?

Paul
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  #2  
Old 09-11-2006, 12:53 PM
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cytoxin cytoxin is offline
 
Join Date: Apr 2006
Location: south carolina
Posts: 1,111
Default no

i remember in school that the tires were not to sit in one spot for more than 14 days yeah right ok well we all know they do. betled tires get this flat spot and once you roll em with some weight on them im sure they'll be good. however if not they will possibly shimmy. 1/8 is almost nothing anyway.
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  #3  
Old 09-11-2006, 12:57 PM
David-aviator David-aviator is offline
 
Join Date: Feb 2005
Location: Chesterfield, Missouri
Posts: 4,514
Default

Quote:
Originally Posted by Paul Eastham
Hey everyone,
When I give my main wheels a spin, there seems to be a flat spot on each tire, perhaps 1/8" out of round. It's not huge, but definitely noticable if you spin the wheel and look at the tire from above.

The fuselage has been on the gear for over a year, but I feel like I have moved it at least every 3 months, hopefully causing a different spot to be on the ground. I have made it a point to not park on the flat spots recently, but the problem is not going away. Tire pressures have been to spec throughout this time, and the overall condition of the rubber looks good to me. I have not flown or taxied the airplane yet.

Should I look into new tires, already?

Paul
My tires get a flat spot if the airplane sits for 2 weeks. Sometimes, like in winter, I can feel a thump-thump during taxi. After a flight, the flat spot is gone.

What you are seeing is normal, IMHO. I wouldn't look into new tires, already.

dd
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  #4  
Old 09-11-2006, 01:07 PM
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Sam Buchanan Sam Buchanan is offline
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Join Date: Dec 2004
Location: North Alabama
Posts: 4,420
Default

Quote:
Should I look into new tires, already?

Yes, you definitely need new tires....send me your old ones......mine are 'bout worn out.
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  #5  
Old 09-11-2006, 04:03 PM
N916K's Avatar
N916K N916K is offline
 
Join Date: Jan 2005
Location: Tehachapi, CA
Posts: 538
Default Tire flat spotting

Quote:
Originally Posted by Paul Eastham
Hey everyone,
When I give my main wheels a spin, there seems to be a flat spot on each tire, perhaps 1/8" out of round. It's not huge, but definitely noticable if you spin the wheel and look at the tire from above.


Paul
Paul

Don't pitch your tire in the trash. In order to remove the flat spotting you have to use your tires. They will have a very large first harmonic for a while but after you get some heat in them, they should clear up.

A little back ground:

All tires will flat spot. In fact it starts as soon as you park your plane, bike, car, whatever. There are many factors that effect the flat spotting, construction material and the position the tire was left have the biggest effect.

Some tire materials will actually cold flow and cause very extreme flat spotting. Nylon is one of the worst for flowing and causing flat spotting. Unfortuanely it's cheap and does very well at high speeds and loads, so it's in most aviation tires along with higher performance car tires. Heat and time is the only way to get most of the flat spot out. It won't come all the way out but over time it will get better.

It is not unusual for a truck or high performance tire to take over 30 miles at 60 mph to reduce a flat spot to an acceptable level.

One way to cut down on flat spotting in to not run the tires against a sharp object, like a wheel chock. Also if you park a hot tire on a cold hanger floor, you may want to roll the plane around a little bit if you happen to still be at the hanger. A cooling tire is a bad case for flat spotting so if you can move the tire deflection around while it cools, you will end up with less flatspotting.

One final note: Most tires are built with a 5 year shelf life. I'm not sure about all aviation tires but all DOT tires will have a date code on them. There will be the letters DOT then a few letters and numbers, at the end will be 4 numbers. That is the week and year the tire was built. 0107 would be the first week of 2007. The date code before 2000 was only three numbers. 017 would be the first week of 1997, 1987, 1977...
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