Good source for tubes?

H. Paul Shuch is a Light Sport Repairman with Maintenance ratings for airplanes, gliders, weight shift control, and powered parachutes, as well as an independent Rotax Maintenance Technician at the Heavy Maintenance level. He holds a PhD in Air Transportation Engineering from the University of California, and serves as Director of Maintenance for AvSport of Lock Haven.

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FastEddieB
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Good source for tubes?

Post by FastEddieB »

When Half Fast and I went to fly my Sky Arrow the other day, the right tire was very low.

Since I had just done an annual, and had the wheels apart, I guess I have to assume a MIF - Maintenance Induced Failure, though it's hard to see how. Very hard to pinch the tube between the wheel halves with some air in the tube. Did not seem to be leaking out of the valve, and even if it was I would think the o-ring on the valve cap would prevent air leakage there.

In any case, we pulled the tube and no damage was obvious. Inflated it and submersed it in a bathroom sink and no bubbles. Went ahead and reinstalled it and flew, and at least over that time span it held pressure.

But of course, I won't know for sure until I head back to the hangar in a day or so. Figure it can't hurt to go ahead and buy a tube (5.00x5) just in case.

Checked Desser Tire first. Anyone found a cheap, reliable source for tubes, other than them, and what brand have you guys settled on? Standard angled stem, BTW.

Thanks!
Fast Eddie B.
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3Dreaming
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Re: Good source for tubes?

Post by 3Dreaming »

I answered on CTFLIER.
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drseti
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Re: Good source for tubes?

Post by drseti »

I have been using Desser for years. I like the free shipping, and the fact that they stand behind their orders (if they inadvertently ship the wrong item - which they've done to me only once -- they immediately make it good).

As for brands, I am a believer in (and user of) Michelin Air tyres. Tubes - not much difference between the different ones.
The opinions posted are those of one CFI, and do not necessarily represent the FAA or its lawyers.
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3Dreaming
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Re: Good source for tubes?

Post by 3Dreaming »

drseti wrote:I have been using Desser for years. I like the free shipping, and the fact that they stand behind their orders (if they inadvertently ship the wrong item - which they've done to me only once -- they immediately make it good).

As for brands, I am a believer in (and user of) Michelin Air tyres. Tubes - not much difference between the different ones.
Based on 35 years working on airplane, I would have to disagree with you on saying there isn't much difference in tubes. Aero Classic Leak Guard tubes have proven to be more reliable over the years.
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FastEddieB
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Re: Good source for tubes?

Post by FastEddieB »

Thanks for all the advice. I have two Aero Classic "Leakguard" tubes on the way from Desser.

And its a good thing. Went to the hangar this afternoon, and the right tire was noticeably bulging again after just two days.

Will look at the old tube more closely and update when I determine from where the air is escaping.

As an aside, the tire on the right is the Air Trak that the Sky Arrow came with, in 2010 after 210 hours:

Image

Below is the Desser Monster retread now, after about 230 hours:

Image

I think its fair to say they wear like iron!

Reminder, these are my 5.00x5 main gear tires.

Again, thanks all for the help!
Fast Eddie B.
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Re: Good source for tubes?

Post by drseti »

Just a reminder to those flying an SLSA (yes, Eddie, I realize yours is an ELSA):

Changing from the aircraft manufacturer's specified tire to any other (especially a retread) will require a Letter of Authorization.

And, yes, I had to get LoAs for both of my SportStars to go from the recommended tire to Michelins. They seem to wear about as well as the retreads Eddie uses (though admittedly more expensive). And, since they weigh significantly more than the originals, I had to redo my weight and balance sheet.
The opinions posted are those of one CFI, and do not necessarily represent the FAA or its lawyers.
Prof H Paul Shuch
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FastEddieB
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Re: Good source for tubes?

Post by FastEddieB »

Update...

Brought the tube home and finally found the leak.

Look at the bubbles along the seam to the left of the valve stem:

Image

Curious is that there seems to be no sign of "insult" to that area once dried off:

Image

So it remains a mystery. My working assumption is that a 6-year-old tube just failed along a seam from nothing other than removing and reinstalling it. Maybe the rubber is getting tired. Maybe its a defect that is only now showing up. I'm open to any other guesses as well.

I will check the inside of the tire at the same position for anything, but again, I don't see anything close to a puncture or slice.

Got the tubes I ordered Friday from Desser today. Probably tomorrow will get out to the hangar to throw one in. I'm going to leave the left one alone for now, but definitely swap it out next annual - if it goes that long.
Fast Eddie B.
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Re: Good source for tubes?

Post by FastEddieB »

The stem junction was the first place we checked - this is on an adjacent seam.

As a data point, this is a "Leakguard" tube, installed with the "Monster" retreads in 2010 and always talc'd.

Three asides...

1) I expected some tire talc from Desser - maybe they only ship it with tires, not tubes, or maybe they just don't provide it for free anymore. I've managed just fine in the past with Baby Powder, so that's what I'll be using this time.

2) I can see the bind mechanics can find themselves in. If I had paid for this annual and had a flat tire a few days later, it would be natural to blame the shop*. When, as best I can tell, technique had little or nothing to do with this failure. Anticept and others - is this something you have to deal with on a semi-regular basis?

3) Again, this was a six-year-old tube. Should they be replaced on a regular basis like the ROTAX rubber parts? If so, is every 5 years a reasonable guideline?


*"Post hoc, ergo propter hoc" - a very common logical fallacy.
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Half Fast
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Re: Good source for tubes?

Post by Half Fast »

Eddie, since you'll scrap the tube anyway, how about slicing it apart and seeing if there's an obvious problem at the seam?

BTW - are your other two tubes the same vintage? You might want to replace them all.
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FastEddieB
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Re: Good source for tubes?

Post by FastEddieB »

Not sure about the nosewheel tube, but it's pretty old. The left main is 6 years old.

Most Conservative Action? Replace them.

As an aside, I tend to save valve caps and cores from old tubes, and if the rubber is still pliable they slice up into great rubber bands!

If I find a defect, I'll let the manufacturer know.
Fast Eddie B.
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Re: Good source for tubes?

Post by FastEddieB »

This should be the final follow-up...

1) The Sky Arrow is easy to jack up, with "naked" gear legs - though I guess that's another thing that adds to the drag and slows it down:

Image

2) The wheel/tire/tube combo renders it nearly impossible to pinch the tube with just a little air in it:

Image

3) Here's how the "Beemer Balancer" works - fits into a sock and all you need is somewhere to hang the string from:

Image

More than one other mechanic has told me 6 years on a tube should be no issue - many tubes go far longer than that. Will probably still replace the left tube next annual if not sooner as the Most Conservative Action - just in case both were from a bad batch made with a weak seam. And I am calling Desser tomorrow to report what seems to be a defect in that one tube.
Fast Eddie B.
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