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Flat tire again

T

terrykohler

Well Known Member
Starting to feel snake-bit. My RV has been pretty much bullet-proof with one exception - tubes. I've had way too many flats over the years (never a problem on my CT210). I've tried different tubes (now using Michelin), had others remount tires for me, gone to and maintain higher pressure (40-45 psi), all without much success. Interestingly, the failures are seldom on the tread side of the tube.
Perhaps it's the wheels??? I can't feel any burrs, but who knows. I've switched tires as well, so the problem isn't likely there.
Can't be over-use, as I'm only flying the plane 100-125 hours per year, and uneven or excessive tire wear is not evident. Brake wear is good.
Has anyone found other wheels to be a fix? Am I alone on this? Suggestions, SWAGS, spitballs, etc. appreciated.
Terry, CFI
RV9A N323TP
 
flats

Hey Terry.
I was having a similar problem. Had 4 flats over a couple hundred hours. All wheels. I have switched mains to mich tubes and now have dessser (sp?) retreads and run a little higher pressure. Also, have sanded inside of rims, used tire talc etc etc..and knock on wood no issues this past year.

I know others with standard vans stuff, never had a single issue. Will be interested what others say. Merry Christmas. :D
 
Tubes

I have used the same set of Michelin Air Stop tubes for 8 years. I add a couple of pounds of air during the conditional inspection and that does it for the rest of the year. Pricey, but worth it!
 
terrykohler said:
gone to and maintain higher pressure (40-45 psi), all without much success. Interestingly, the failures are seldom on the tread side of the tube.
Click to expand...

These small tires are more prone to flats. In my experience your pressure is too low. I try to maintain at least about 45 psi. Many Lancair guys with the same tire/wheel as the nosewheel in our RV-9A maintain 55-60 psi.

Some have the theory that the tire will spin on the wheel pinching the tube. My theory is the tire will flex on the rim pinching the tube. This happens when the pressure decreases. Wheelpants on the RV's make it more of a PITA to check pressure. Also, on the Lancair without wheelpants I can just glance at the tire and tell if it needs air. So, less checking for needed air leads to operations with lower air pressure leads to flats.

There is another option but it'll cost you. Beringer makes a wheel / brake combo that takes a tubeless tire. I hear rave reviews on it for smoothness and no flats...
 
my thought is the tubes are low quality. i now carry a bike tire inflator in case i need to reinflate to get home. mine was a slooow leak. do what you can, carry some spare tubes and a way to air up, and enjoy the flying. :)
 
turbo said:
my thought is the tubes are low quality. i now carry a bike tire inflator in case i need to reinflate to get home. mine was a slooow leak. do what you can, carry some spare tubes and a way to air up, and enjoy the flying. :)
Click to expand...

Every time I have had a flat there was evidence of pinching on the lateral aspect of the tube. Cannot blame the tube for failure when it gets pinched.

I carry spare tubes and all the tools required to change it other than air. I just need to locate air on site.

I know of some who carry a whole spare tire/rim ready for installation.
 
Any Experience With Tubeless?

Ron B. said:
Are you using plenty of tire talc powder?
Click to expand...

Yup. Plenty of talc. I've been running 45 psi, but based on comments so far, I'll likely disassemble, sand/polish the wheel surface, and try 55-65 psi. If that doesn't work, I may be headed to tubeless.
Terry
 
terrykohler said:
Yup. Plenty of talc. I've been running 45 psi, but based on comments so far, I'll likely disassemble, sand/polish the wheel surface, and try 55-65 psi. If that doesn't work, I may be headed to tubeless.
Terry
Click to expand...

I think the talc is indeed the key for the problem as you've described. It needs to be rubbed all over the tube and on the inside of the tire.

Re sidewall tears in the tube, my theory is that there is a progressive stretching of the inner tube where it contacts the sidewall, due to flexing from rolling. If the friction between the tube and the tire is high enough, the tube can be stretched past its limit. The OP did not say specifically where they were other than not on the tread.

Also, use caution with the higher pressure - you may get quite a bit of shimmy. I missed which wheels were having flats - main or nose or both?
 
AlexPeterson said:
I think the talc is indeed the key for the problem as you've described. It needs to be rubbed all over the tube and on the inside of the tire.

Re sidewall tears in the tube, my theory is that there is a progressive stretching of the inner tube where it contacts the sidewall, due to flexing from rolling. If the friction between the tube and the tire is high enough, the tube can be stretched past its limit. The OP did not say specifically where they were other than not on the tread.

Also, use caution with the higher pressure - you may get quite a bit of shimmy. I missed which wheels were having flats - main or nose or both?
Click to expand...

Alex:
I think I've got plenty of talc. Most of the tube failures have been on the ID or part contacting the wheel. Flats are happening on mains. My touchdowns are typically not high speed (55-60kts on final), very little braking used (long, paved runways), and turnoffs pretty gentle. I do, however, operate quite often at or near gross (1750-1800). Still scratching my head on this one.
Thanks,
Terry
 
Just one more data point regarding talc.
I don't use it. Zero, none, nada. Not saying it would hurt mind you, just that I for one don't use it.

Every single time I have had a flat I had a corresponding lack of tire pressure due to allowing the pressure to drift down with time. It got to the point that I could predict when it would happen based on the shape of the tire where it contacts the ground. I have never had a flat when I maintained tire pressure in the 45 psi plus range.

terrykohler said:
Most of the tube failures have been on the ID or part contacting the wheel. Flats are happening on mains.
Click to expand...
This is exactly consistent with my experience.

The prior caution regarding shimmy with increased pressure would be good to watch for. I have read of it being reported though have not personally experienced it.
 
Last edited:
8 years on vans original stock.
No flats or slow leaks.
Use talc
45psi.
Inspect tubes & rims every change.
Using green scotchbrite on rims prior to mounting
 
flats and rounds

Saw an RV8 on the ramp at my field a week ago.... nose going flat.
Note to self, always carry a spare tube.
The little 4 inch is not easy to come by at a maintenance shop.
In the end, I removed the entire front wheel from my 9A and sent him on his way home before dark. Few days later, he put it back on my airplane while I was out of town in another plane... all is well.
Spruce order for spares is in. And by the way.... don't trust a HF cheapo air gauge.... the results are all over the place in PSI.
 
These little tubes are available on short order if need be at Tractor Supply. They've got what you need out there...
 
I use the stock tires from Vans with the tubes, I only run 38PSI and have not had a flat but did have a problem with the tires leaking only to find out the valve stems on the tubes that Van's supplies are not the greatest. I got a set of new stems from NAPA that look to have a silicon seal on them. I made sure they were put in tight and have not had a problem since. I have found out running the tire pressure at around 38 for my plane eliminates any shimmy, I guess the tire does not transmit as much vibration to the gear assembly.

Smilin' Jack
 
Thanks for the Input

I'm going to try to make it to the airport tonight and get the wheel off and into a warm workshop at home.
Confession: While I've done a cursory hand check of the wheel surfaces at each change, I haven't polished surfaces or used scotchbrite. This time I will.
I'm going to stick with the Michelin tubes again. Yet to be purchased.
Will plan to report on the forums a few months down the road.
In the meantime, I think I'll look for a small, high quality bicycle hand pump that I can carry on board. Fingers crossed. Hope springs eternal.
Terry, CFI
RV9A N323TP
 
terrykohler said:
...

I do, however, operate quite often at or near gross (1750-1800).

....
Click to expand...


Terry could this be a contributing factor? Compounded with a transition student introducing a little side load on touchdown? Just a thought our wheelies are small indeed the other day I met a Skycatcher not far from my local airport with a flat of this symptom. He has our wheels.
 
terrykohler said:
I'm going to try to make it to the airport tonight and get the wheel off and into a warm workshop at home.
Confession: While I've done a cursory hand check of the wheel surfaces at each change, I haven't polished surfaces or used scotchbrite. This time I will.
I'm going to stick with the Michelin tubes again. Yet to be purchased.
Will plan to report on the forums a few months down the road.
In the meantime, I think I'll look for a small, high quality bicycle hand pump that I can carry on board. Fingers crossed. Hope springs eternal.
Terry, CFI
RV9A N323TP
Click to expand...

And don't forget the generous talc usage.

I have yet to fly, and assumed my previous owner did all this, but your thread has prompted me to dissemble and ensure all these criteria are met. Thanks.
 
When using talc, is it important to wipe the rim clean of talc before final assembly of the rims? The purpose would be to prevent the tire turning on the rim (on touch down) possibly stressing the valve stem where it comes through the hole in the rim causing a leak. Or does the whole tube turn with the rim, and not the tire?

Bevan
 
Bevan said:
When using talc, is it important to wipe the rim clean of talc before final assembly of the rims? The purpose would be to prevent the tire turning on the rim (on touch down) possibly stressing the valve stem where it comes through the hole in the rim causing a leak. Or does the whole tube turn with the rim, and not the tire?

Bevan
Click to expand...

The talc is to encourage the tube to slide easily during the early stages of inflation, to prevent folds and pinches in the tube.
On touchdown all of the rotational forces should be transferred from the tire bead to the wheel rim, none thru the tube. If the tube does move relative to the wheel you will shear off the stem.
 
BobTurner said:
The talc is to encourage the tube to slide easily during the early stages of inflation, to prevent folds and pinches in the tube.
On touchdown all of the rotational forces should be transferred from the tire bead to the wheel rim, none thru the tube. If the tube does move relative to the wheel you will shear off the stem.
Click to expand...

What I meant to say is will the talc on the edge of the rim promote slippage of the tire on the rim? And if so, could this cause a stem leak?

Bevan
 
Using no talc for the last 800 hours or so in my Lancair I have never had a stem sheared off, nor heard of that failure from others on the Lancair forum. I may be mistaken but I believe these flat tires are more common on the 2 seat Lancair variants (235,320, 360) than in the RV's. This may be due to less shock absorption in the gear of the Lancairs or possibly because all 3 tires on those Lancairs are the same size as the nose wheel on our RV-9A. I believe the smaller tire is more prone to flats. Anecdotally, we have never experienced a flat on our RV with about 200 hours in it now.

It is a frequent enough failure that at least one of the Lancair transition instructors will carry a spare wheel / inflated tire assembly with him when going to give transition training.

I believe that it is easy for the tire pressure to creep down and go unnoticed. Unless we check air pressure every time we fly, which I do not do and doubt many of us do, we are possibly flying with lower air pressure that we realize. On the Lancair forum it is widely agreed that the common factor in flat tires is low air pressure. The common finding is scuffing / pinching along a lateral margin of the tube. As a result of numerous flats (to the point that I accurately predicted when it would occur but flew anyway to beat a rapidly approaching low overcast with ice only to land and get a flat upon landing) I am convinced increased air pressure is key to preventing it, and in fact have never experienced a flat with higher air pressure. Because I do not check every time, I will typically fill to the high side (as high as 60 psi) and plan to refill when it gets as low as 45 psi (which can be estimated by visually inspecting the curvature of the side of the tire in contact with the ground).
 
Flats

Before, 3 flats, pressure to low. I have been using 50+ PSI with no flats for 400 hrs. RV6A. Lots of talc.
 
I've probably said it a million times, but might as well say it one more time -
I guarantee to following is true:

LOW PRESSURE = TIRE FAILURE

My recommendation, use 45-50 psi all around (if possible), check and re-inflate every 45-60 days, flats will be a thing of the past.
35-40 psi should be an absolute minimum.
 
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I use 40 in the mains. Initially was using less but the wear was too excessive. I don't know what the max would be. Isn't it on the side of the tire/tube?
 
An old thread reopened.

The max pressure of the tire is stamped on the sidewalls.

I run all three tires on my 6A at 50 psi.
 
Wheel chocks

If you use wheel chocks that are a "U" shape, a low tire will make itself known by how easy the chock goes around the wheel.

I made wheel chocks from PVC and 2 elbows and 2 endcaps that just fit around the tire. If I have to force or wiggle them to get around the tire, then I have an early indication of low pressure.

Not a perfect tire pressure gauge but useful.
 
Reinflate

On initial tube & tire install I have always used talc. Nothing excessive. I inflate tire without the scrader valve in and inflate and deflate several times. It seems to "relax" the tube and position the tube in the correct position. Install valve and inflate to preferred psi....
 
Walt said:
I've probably said it a million times, but might as well say it one more time -
I guarantee to following is true:

LOW PRESSURE = TIRE FAILURE

My recommendation, use 45-50 psi all around (if possible), check and re-inflate every 45-60 days, flats will be a thing of the past.
35-40 psi should be an absolute minimum.
Click to expand...

Another guarantee is that high pressure = less vibration damping. One needs to find the balance for your airframe. I would like my mains to be at 50 (for easier pushing), but I get a nasty resonance at that pressure. I have to keep the mains between 35-40. No main flats in 1500 hours. Several nosewheel flats in the first couple hundred hours before using a lot of talc. None since.
 
Got a nose wheel flat. Changing tube on the ramp. Not at home. What are the torque values for rim bolts and axle bolt? Thanks
 
FORANE said:
I believe that it is easy for the tire pressure to creep down and go unnoticed.
Click to expand...
I check mine about every two weeks and yes, I usually lose 2-5 psi between checks. I run all three of mine at 50 psig (nitrogen). I carry a spare tube with me.

Oh yeah, I use talc between the tire and tube, and use Parker O-Lube on the tube and wheel halves during assembly so (hopefully), the tube doesn't get pinched between the wheel halves. The O-lube dries up after a while and I've never had any problem with slippage.
 
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Are you guys running Airstop tubes? I'd be concerned to learn that they're leaking down 2-5 PSI in two weeks.
 
snopercod said:
use Parker O-Lube on the tube and wheel halves during assembly so (hopefully), the tube doesn't get pinched between the wheel halves.
Click to expand...

Take a piece of thick paper or thin cardboard, cut it in a strip about 2 inches wide and 14 inches long. Put the tube in the tire. Inflate the tube slightly. Mount the tire/tube with the valve stem in the rim half that has a hole for the stem. Tuck the paper/cardboard strip in the tire between tire beads starting on one side of valve stem and continuing to the other side of the valve stem. Slide the other rim half on leaving the paper in place. The paper prevents the tube from getting pinched.
 
kbalch said:
Are you guys running Airstop tubes?
Click to expand...
I'm running LEAKGUARD INNER TUBE 11X400-5 TR87 from ACS. I may have exaggerated how much pressure I lose between checks. It's probably closer to 2 psi between checks. I think it depends upon the weather (or maybe the number of hard landings :D ) Also, I lose a little pressure every time I apply the pressure gauge, so maybe that explains the loss. These Lancair tires are small so it doesn't take much. For the record, I've never had a flat.
 
Desser came through and overnight delivered an innertube for the nose wheel. I will reassemble tomorrow am and should be off. Aeroclassic 11/400-5.

I have been purposely underinflating the nose wheel tire as it dampens the wiggles nicely but I think that was the reason for the flat.
Thanks for all the help.
 
Been using Dresser monster tires and tubes. They wear like iron and have not had a problem. Only complaint. The tubes are about same price as the tires
 
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