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  #1  
Old 01-16-2020, 06:36 AM
humptybump humptybump is offline
 
Join Date: Feb 2011
Location: USA
Posts: 3,174
Default Random flat tire / tyre ?

What might cause the following:
  • Went to the hangar and one tire was flat.
  • It wasn't flat the day before or the day before that.
  • I had flown 7 days prior.
  • Put air in the time and it's been 24hr and it's still at same pressure. (will continue to monitor for multiple days.)
  • No externally visible signs of trauma.
  • Local weather has been moderate. Hangar temps have remained in the range of 48F-64F.
  • No climatic evidence on the airplane.
  • No visible stresses evident on the plane.

I want to monitor for another 48 hours before I remove the wheel and do a soap-bubble test.
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  #2  
Old 01-16-2020, 06:55 AM
moosepileit moosepileit is offline
 
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Location: Floyds Knobs, IN
Posts: 564
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BLUF- look for a tube manufacture flaw, a pore in the surface that leaks, removed from tire, with about 8psi in the tube to stretch it enough. Mine was stem outlet side wall location across from the stem outlet. - no way it was a puncture. It was a flaw that looked like a little pit/pore.

Longer version:

This year I had very similar on on a Michelin Airstop tube molded 10/2014. Random flat in hangar. No obvious damage, cut, tear pinch or recent work.

Funnier part was I had a metal valve stem cap that would over-screw and was misformed and actually give a hiss of air when unscrewed. I thought the stem seal was bad, it was not. Fix- I then thought- new valve cap.

Glad I left the wheel pant off overnight because the real leak was a pore in the innertube manufacture defect. I had to put 8 psi in the tube, free of the tire to find it. That was the hard part- that seemed excessive, but without it the leak did not show uo readily.

http://www.vansairforce.com/communit...Tube+stem+leak
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Last edited by moosepileit : 01-16-2020 at 12:26 PM.
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  #3  
Old 01-16-2020, 06:59 AM
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emsvitil emsvitil is offline
 
Join Date: Oct 2019
Location: SoCal
Posts: 120
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If tubeless, I'd say a nail or similar is in tire.

Normally nail will plug hole.

But if you happen to stop 'just so' on the nail, air leaks out.
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  #4  
Old 01-16-2020, 07:08 AM
humptybump humptybump is offline
 
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Location: USA
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Tubed tires. No nails or damage to tyre. Could be minute damage to stem. These tires and tubes are 3 seasons and have been rotated once.

I'll monitor for another 1-2 days and the. Remove to test with soapy water.

I doubt I would find anything definitive without doing the water test and it provides that next-level confidence.

Last edited by humptybump : 01-16-2020 at 07:15 AM.
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  #5  
Old 01-16-2020, 07:10 AM
BH1166 BH1166 is offline
 
Join Date: Nov 2017
Location: Eatonton Georgia
Posts: 150
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Had similar situation but had checked air pressure days before. Like you flew no issues, landed, stored 5 days later flat. Inflated back up, has held for 6 weeks. I blame the schrader valve for not seating properly and created a very slow leak, only visible after days of leaking.
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  #6  
Old 01-16-2020, 07:29 AM
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Walt Walt is offline
 
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Quote:
Originally Posted by humptybump View Post
Tubed tires. These tires and tubes are 3 seasons and have been rotated once.
I think many folks under estimate the importance of tires and brakes, failures of either can really make for a bad day and be very expensive!
Personally if I remove a tire it generally get a new tire/tube, or at least a new tube, I don't 'flip' tires for this reason.

From the good folks at Goodyear Tire:

"It is recommended that tubes not be reused; they can grow as much as 25% in service. Reusing them can result in folded, pinched tubes which can fail or create an imbalance."
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Last edited by Walt : 01-16-2020 at 08:06 AM.
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  #7  
Old 01-16-2020, 07:32 AM
Feetwet Feetwet is offline
 
Join Date: Mar 2008
Location: Seattle/Tucson
Posts: 52
Default Tube problem

I have had a similar problem with tires with a tube in them. What I think happens is the tire itself retains some air in it while the tube is filled, and that air balances with the pressure in the tube at 25-30 psi. Then after a couple days, the air that was left in the tire leaks out leaving only the air in the tube and a partial flat. When this occurred I refilled the tube to the 25-30 psi, and it was fine after that.
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  #8  
Old 01-16-2020, 07:36 AM
humptybump humptybump is offline
 
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Location: USA
Posts: 3,174
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Quote:
Originally Posted by Walt View Post
"It is recommended that tubes not be reused; they can grow as much as 25% in service. Reusing them can result in folded, pinched tubes which can fail or create an imbalance."
I always replaced tubes with tires But kept tubes with tires. Each of the A&P 's who have done my condition inspection have instructed me on the process of flipping the tires and never suggested replacing tubes during the process.

Walt, does this mean that tubes should be replaced every time the tire comes off - even when flipping the existing tires?
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  #9  
Old 01-16-2020, 08:13 AM
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Walt Walt is offline
 
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Quote:
Originally Posted by humptybump View Post
I always replaced tubes with tires But kept tubes with tires. Each of the A&P 's who have done my condition inspection have instructed me on the process of flipping the tires and never suggested replacing tubes during the process.

Walt, does this mean that tubes should be replaced every time the tire comes off - even when flipping the existing tires?
Unless it's a field repair/emergency, new tubes should be installed when the tire is removed, this includes 'flipping'.

I know lots of folks won't agree with me because it costs to much, try having a flat at an airport away from home and then tell me how much you spent fixing it.
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EXP Aircraft Services LLC
Specializing in RV Condition Inspections, Maintenance, Avionics Upgrades
Dynamic Prop Balancing, Pitot-Static Altmeter/Transponder Certification
FAA Certified Repair Station, AP/IA/FCC GROL, EAA Technical Counselor
Authorized Garmin G3X Dealer/Installer
RV7A built 2004, 1700+ hrs, New Titan IO-370, Bendix Mags
Website: ExpAircraft.com, Email: walt@expaircraft.com, Cell: 972-746-5154
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  #10  
Old 01-16-2020, 08:23 AM
lr172 lr172 is offline
 
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Location: Schaumburg, IL
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Losing all air in one day is not a slow leak, it is something significant. It could have been an issue with the shrader valve, but that is only likely if the valve was used just before the leak event. If you haven't touched the shrader valve in some time, it is far less likely to be a stuck or mis-seated valve.

Whatever it was is likely to happen again, so either identify the issue or replace the tube, lest you get stranded some day or worse, find yourself landing with a flat tire. A tire can't lose that much air in a day without a major fault.

Larry
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Last edited by lr172 : 01-16-2020 at 08:25 AM.
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