Tire pressure revisited

[cnoe]

I experienced a rapid decompression while taxiing my 201 on Saturday. Within a couple of seconds I had the right main completely flat with the inner gear door resting not-so-comfortably on the asphalt. I managed to block the primary taxiway of this smaller airport on the outskirts of Houston for about an hour while a crew came out to fix it.

 

Turned out that the tire was fine but the valve stem was ripped completely off the tube (while taxiing). I KNOW the tire wasn't low as I had adjusted the inflation less than 24 hours prior and had done a thorough pre-flight.

 

Still, the mechanic said that this was caused by underinflation. He was surprised to find the placarded pressure to be 30 psi (in the mains) and even looked at my POH to confirm that. He said they always put 35-40 psi minimum in 6-600 6-ply mains to keep the tires firmly seated on the rims.

 

This Desser tube was only 1 year old and was part of a tire/tube package (Michelin Aviator tire).

 

Anybody else have this issue, or have any comments? I may opt for a name-brand tube in the future and will likely run with a bit higher pressure.

 

Cnoe

 

 

[jetdriven]

Yes both desser tubes failed on me, they are garbage. The first wouldn't hold air overnight. The second failed just after a flight when I taxied to the fuel pump. It was a year old. Both were leaking where the stem was bonded to the tube.

[Jerry 5TJ]

The PA46 community's MMOPA site has several threads on inner tube failures. 

One well-respected and active PA46 mechanic (Chad Menne) posted this:

 

"I wish I could point you to the best brand, but unfortunately I have seen all brands of butyl tubes fail in the exact same way, seemingly at an equal rate. If you want to improve your chances of not having a flat, then use natural rubber tubes, but then be prepared to add air every couple weeks. I finally had my first tube failure in a customer's plane a couple months ago, after over 9,000 hours of PA46 flight hours. It can be very disruptive to your schedule and can potentially lead to aircraft damage if you lose control on landing, but in most cases, the tire goes flat when the plane is sitting, rather than when in the air. I'm not exactly sure why."

[MyNameIsNobody]

Desser is now "on my list"...

Thank you.

[Hank]

I've had good luck the last 7 years with Michelin airstop tubes and Goodyear tires at 30 psi.

[cnoe]

So I called Desser and inquired about the failure history with their LeakGuard (oxymoron?) tubes and of course they said that the tubes were very good quality. I was told that the Michelin tubes were no better, but I'm not so sure. A friend who runs a flight school says they've had bad luck with anything but name-brand tubes even though I believe even the Michelins are manufactured overseas. Desser did offer to "look at the tube and maybe replace it" if I'd send it in at my expense; the problem is that I don't want the same brand tube now, so I likely will just blow that off.

 

So what brand did you go to Byron; sounds like Hank is satisfied with the Michelins? I may try those.

 

In the meantime I'm running higher pressure in the mains to possibly help avoid this issue.

 

Cnoe

[M20F]

Make sure you put some tire talc on the tubes. i have read baby powder has some abrasives in it which makes it not a good substitute.

[MB65E]

Michelin leak stop tubes have been awesome! I like the Goodyear Flt III's tires on most installs. I think I'd rather stay with a nicer tube than a nicer tire. Espically in the lighter M20's. J's and lighter...

Goodyear has had several tube issues in the past. I have never seen a Michelin tube issue or failure in 12-15 years.

I'd stick to what the POH says regarding pressure, and try to use Nitrogen. It will last longer than shop air.

-Matt

[Hank]

I've never understood the whole "fill your tires with nitrogen" thing, other than as a money-maker for shops that charge $50-$100 for the "service." Regular air, that we breathe and compress in our hangars and garages, is already 78% nitrogen . . . The size difference between molecules of N2 and O2 is not significant; there is 21% oxygen, and the reminder is just trace elements like hydrogen, helium, CO, CO2 and the many noble gases.

I fill my tires (bicycle, mower, car, truck and airplane) with genuine compressed air, and don't worry about the 22% that isn't nitrogen. And I fill them all as recommended--bike 105, car 32, truck 35, Mooney 30; don't recall ever reading a recommendation from John Deere.

[carusoam]

Too many things to go wrong with over or under inflating.

If over inflating is the plan to keep from having an under inflated tire.

Desser is a 'name brand'. Maybe not the name brand that you want...

Check your other tires to see how well centered the stem is. If the tire gets low on airpressure and the stem migrates, there is more stress on the stem than it can take?

Full conjecture, my C got air every month. My R goes months before getting air...

Best regards,

-a-

[MB65E]

Hank, I here you. All I know is if I use shop air I need to fill the tires every month. (In non leak stop tubes). If I use N2 on the same tube Combo, it last several months with out needing a fill.

I know...

-Matt

[clh]

Hey, cnoe,

 

I think you have seen a dresser tube fail before.........

[cnoe]

Hey, cnoe,

 

I think you have seen a dresser tube fail before.........

That's right! My first ride in a Mooney was preempted by a taxiway flat. I wasn't paying attention to the details at that time; thanks for the note.

Looks like Chief has the best price on Michelin LeakStops. On the list now.

Cnoe

[cliffy]

A couple of items come to mind, Seems I read somewhere that there a 2 different lengths

of valve stems available on 600x6 tubes, Short and long. The long ones seem to be impacted

by the wheel hub cap and force them to remain "bent" thereby setting up stress on the "long"

wall of the bend, right whereif exits the wheel hole and causing stress and heat cracks rather quickly.

Looks like a long stem is shown'

Short stem tubes are very hard to find in my experience but they can be found.

Another option that was mentioned to me was to use an 800x6 tube with the 90 degree brass valve stem.

The tube size fits the tire size even though it eays 800 and it is supposed to last for the life of the

tire or so hangar fairies tell me.

[Guest Eagle2]

I've never understood the whole "fill your tires with nitrogen" thing, other than as a money-maker for shops that charge $50-$100 for the "service." Regular air, that we breathe and compress in our hangars and garages, is already 78% nitrogen . . . The size difference between molecules of N2 and O2 is not significant; there is 21% oxygen, and the reminder is just trace elements like hydrogen, helium, CO, CO2 and the many noble gases.

I fill my tires (bicycle, mower, car, truck and airplane) with genuine compressed air, and don't worry about the 22% that isn't nitrogen. And I fill them all as recommended--bike 105, car 32, truck 35, Mooney 30; don't recall ever reading a recommendation from John Deere.

Good afternoon folks, if I may comment on the use of nitrogen (100%) in aircraft tires. The USAF uses 100% nitrogen in all of our (your) aircraft for one very important reason. It is DRY (non corrosive) and does not contain the inert gases and moisture that you mentioned. If you follow the recommendations on your home air compressors it tells you to periodically open the drain valve on the bottom of the tank. If you do this, most likely you will see rusty water come running out. Not something any of us want in our aircraft tires. 

 

   Be safe, Ron

[PaulB]

Is rim corrosion that common? What about in car? Anyone use nitrogen in their car tires?

[Guest Eagle2]

Is rim corrosion that common? What about in car? Anyone use nitrogen in their car tires?

 

Hi Paul, not sure about rim corrosion in the GA fleet. But again in the Air Force, we do not. And yes this spring when I had new Michelins put on my wives Lexus at Costco, I opted for the nitrogen fill. Simply explaining the reason, take it or leave it.

 

 Ron

[Piloto]

I had the same Michelin tubes for over three tires replacements and they still hold pressure. The pressure on the tire changes with ambient temp and weight (fuel) on the plane. 30 psi is ideal for hard surface taxing. Less bumpy on landings and taxing. But for operation on grass 35 psi is better to avoid high power taxing and longer takeoff runs. If you are hand towing over grass or over hangar door tracks 40psi will keep you from having a heart attack.

José

[jetdriven]

Good afternoon folks, if I may comment on the use of nitrogen (100%) in aircraft tires. The USAF uses 100% nitrogen in all of our (your) aircraft for one very important reason. It is DRY (non corrosive) and does not contain the inert gases and moisture that you mentioned. If you follow the recommendations on your home air compressors it tells you to periodically open the drain valve on the bottom of the tank. If you do this, most likely you will see rusty water come running out. Not something any of us want in our aircraft tires.

Be safe, Ron

I don't know how the rubber can get corrosion. Air inside the tube won't corrode the wheel. The real reason for nitrogen is it doesn't change PSI as much with the serious temperature changes that aircraft tires endure.

Wheel corrosion is a serious deal. That magnesium is ridiculously soft and corrosion prone, and brake dust as well as water or anything else can make it start pitting, it doesn't take much at all to scrap a wheel. A wheel half is like 350$ while a whole wheel is 5 something. Plus labor. Plus paint. Plus a new tube and most likely s new tire too, so it runs over a grand pretty easily, and the plane has 3 of them.

Based on this, the last time I changed tires, I stripped the wheels, treated with PreKote, baked in an oven (the metal sweated the water out), primed them painted them. PreKote or chromic acid, and baking is the key. Two years on the still look new. Aircrsft paint shops still haven't figured this out. You get your Bonanza back and man it looks nice, 13 months later there is filiform corrosion under the paint and the paint shop won't pay it. It's around 10k to get them re skinned.

[jetdriven]

I had the same Michelin tubes for over three tires replacements and they still hold pressure. The pressure on the tire changes with ambient temp and weight (fuel) on the plane. 30 psi is ideal for hard surface taxing. Less bumpy on landings and taxing. But for operation on grass 35 psi is better to avoid high power taxing and longer takeoff runs. If you are hand towing over grass or over hangar door tracks 40psi will keep you from having a heart attack.José

I like them a little over inflated as well. The last tube I reused it failed a couple days later. The nose tire it was, it closed the runway and the prop was less than 1 inch from the pavement. Seems they stretch and they don't recommend re-using them.

[Guest Eagle2]

I don't know how the rubber can get corrosion. Air inside the tube won't corrode the wheel. The real reason for nitrogen is it doesn't change PSI as much with the serious temperature changes that aircraft tires endure.

Wheel corrosion is a serious deal. That magnesium is ridiculously soft and corrosion prone, and brake dust as well as water or anything else can make it start pitting, it doesn't take much at all to scrap a wheel. A wheel half is like 350$ while a whole wheel is 5 something. Plus labor. Plus paint. Plus a new tube and most likely s new tire too, so it runs over a grand pretty easily, and the plane has 3 of them.

Based on this, the last time I changed tires, I stripped the wheels, treated with PreKote, baked in an oven (the metal sweated the water out), primed them painted them. PreKote or chromic acid, and baking is the key. Two years on the still look new. Aircrsft paint shops still haven't figured this out. You get your Bonanza back and man it looks nice, 13 months later there is filiform corrosion under the paint and the paint shop won't pay it. It's around 10k to get them re skinned.

Really??????????????? Do you actually think I was saying the rubber would corrode??????????????? Why do you have to continually add air to your tires, because the rubber leaks! Yes your right wheel corrosion is a serious issue, thats why the US military uses NITROGEN to fill tires. And temperature change is not the real reason for using nitrogen genius (actually very minimal), I just explained the REAL reason to you. AGAIN question asked, reason given you can make up all the crap you want. 

[jetdriven]

You are saying that the military uses nitrogen to protect against wheel corrosion, that's great but these tires are not tubeless.

[jetdriven]

I edited that out but you know what, it fits.

[Guest Eagle2]

I edited that out but you know what, it fits.

Impossible to tell that from typing words on a keyboard Byron……Cheers.

[Hank]

A properly maintained compressor will filter out water. Inert gases, being inert, do not react--that's why they are called "inert."

Both of you, please stop the squabbling and name calling, it's detracting from the discussion here. I'm glad the USAF is protecting their magnesium wheels from the inert gases that don't react with anything. I suppose a nitrogen separator is cheaper to run and maintain than an air compressor? And that it magically sorts 100% of the water out while separating N2 from the atmosphere, and not reintroducing any while compressing the N2.