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  #21  
Old 01-19-2020, 01:28 AM
JDeanda JDeanda is offline
 
Join Date: Apr 2013
Location: Ventura, CA
Posts: 273
Default Valve Stem, Maybe?

In a conversation with an automobile designer/entrepeneur many years ago, he told me "An intermittent leak is ALWAYS a valve stem!" Reading previous posts makes me doubt that this is always the case, but it might be a good idea to replace the valve stem. It only costs pennies although you will need to support the airplane when the tire is dead flat, but it might be worth a try.
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  #22  
Old 01-19-2020, 11:13 PM
JDeanda JDeanda is offline
 
Join Date: Apr 2013
Location: Ventura, CA
Posts: 273
Default Intermittent Leak

Many years ago, an old automotive designer, entrepreneur and pilot told me that "an intermittent leak is ALWAYS a valve stem!" Shouted it, actually. Reading previous posts to this thread convinces me that the valve stem is not necessarily the only answer. But it only costs pennies and it's fairly easy to do... you will need to support the airplane to keep weight off the tyre until you're done. Worth a try.

jerry
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  #23  
Old 01-20-2020, 06:55 AM
Dean Pichon Dean Pichon is offline
 
Join Date: May 2006
Posts: 555
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I experienced the same problem this past weekend. Saturday morning, I found the left main dead flat on my -4. The week before, I flew and it was fine. The last time I touched the wheel was to add some air in November. (I add air about every 6 months.) I have flown every weekend since adding air.

I pulled the wheel and while doing so, decided I should replace the brake pads since I had everything open. Once I decided to do the left pads, I thought I might as well do the right.

So my flight was scrubbed, I and pulled off both wheels instead. I have ordered replacement pads, Airstop tubes, and Condor tires (>$500). Yesterday, I submerged the bad tube in a sink full of water, but could not find a leak. After 24 hours, the flat tube appears to be holding pressure.

Airstop tubes cost more than the tire, so I do find this exercise a bit frustrating...
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  #24  
Old 01-29-2020, 05:59 AM
humptybump humptybump is offline
 
Join Date: Feb 2011
Location: USA
Posts: 3,181
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Closing out my post ...

I replaced the valve core and it appeared to solve the problem ... but it didn't. It did dramatically slow the leak but it still wasn't "done".

I replaced the tube.

Case closed without solving the mystery.
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  #25  
Old 01-29-2020, 06:52 AM
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Vlad Vlad is offline
 
Join Date: Oct 2008
Location: Utah
Posts: 8,440
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Glen I know how you like to experiment. Over inflate the discarded tube and do a bubble test. The offending micro crack will reveal itself
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  #26  
Old 01-29-2020, 07:28 AM
RV10Man RV10Man is offline
 
Join Date: Jan 2005
Location: Oklahoma City, OK
Posts: 1,167
Default

I had a similar issue with the rear tire on my Goldwing.
I had new tires installed before we left home in Oklahoma to Williams, AZ. Two day trip to AZ was fine, along with the couple of days we were there. On the way home, at one fuel stop, I didn't think the rear tire looked quite right. Sure enough it was really low, so I aired it up at the pay pump. It remained good all the way home.

When we got home I took it to the Honda shop where I had the tires installed. They couldn't find any air leaks at all. It was there a few days, so they called me to say it was ready. Went to pick it up, the back tire was flat.

The only thing we could figure, was it was separated on the inside and when parked in just a certain position it would open the separation enough to leak.
They put on a new tire under warranty, I haven't had any trouble since.
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  #27  
Old 01-29-2020, 08:12 AM
humptybump humptybump is offline
 
Join Date: Feb 2011
Location: USA
Posts: 3,181
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Quote:
Originally Posted by Vlad View Post
Glen I know how you like to experiment. Over inflate the discarded tube and do a bubble test. The offending micro crack will reveal itself

I may just do that.


I will point back to Walt's post to replace tubes even when flipping tires. When I did the mild inflation test of the tube to check for leaks, it was definitely not uniformly round any more.
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  #28  
Old 01-29-2020, 10:23 AM
Dean Pichon Dean Pichon is offline
 
Join Date: May 2006
Posts: 555
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Quote:
Originally Posted by Vlad View Post
Glen I know how you like to experiment. Over inflate the discarded tube and do a bubble test. The offending micro crack will reveal itself
I just fixed my flat by replacing both tubes, both tires, (and brake pads for good measure). I inflated both old tubes (the one that flatted and the one on the other side) to 8-10 psi. Neither showed a leak by submerging. After 7 days, I could not discern a pressure difference between the two. It's still a mystery to me.

To what level can a tube without a tire be pressurized without rupturing the tube?
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  #29  
Old 01-29-2020, 04:13 PM
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catmandu catmandu is offline
 
Join Date: Dec 2005
Location: Sierra Nevada
Posts: 1,010
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Quote:
Originally Posted by Dean Pichon View Post
To what level can a tube without a tire be pressurized without rupturing the tube?
Hold my beer . . .
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Sierra Nevada
RV-6A bought flying (for sale soon)
Super-8 bought flying
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  #30  
Old 01-30-2020, 09:10 PM
Mconner7 Mconner7 is offline
 
Join Date: Feb 2018
Location: Bradenton FL
Posts: 115
Default -10 flat

I had a tire go flat in a similar time frame. I pulled the tube out and pumped it up to about 150% of of its size and found a small crease in the tire had worn it through. I will not re-use tubes.
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