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Tire Problem

pilotyoung

Well Known Member
I am posting this situation to keep someone else from making the same mistake I did. I am a new owner, I bought my RV-12 in February 2018. I have been a pilot for many years, but am new to maintenance.

Saturday I flew from KEET to KBGF to attend a fly-in breakfast. I took a friend with me so we could enjoy the fly-in together.

When I landed at KBGF I could not steer the aircraft. It started going left and nothing I could do would stop it. I was able to miss a taxi light by using the left brake. The aircraft ran off the runway into the grass and did a 180 before it stopped. So we were sitting in the aircraft, facing the way we flew in, and not knowing for sure what happened. I thought the left tire had blown.

We got out of the aircraft and the left tire was flat. The aircraft has slid on the wheel pants on the runway before it exited to the left. The airport manager and a couple other people came out to see if we were OK and we were. They help me jack the aircraft up, get the wheel pant off, and then we were able to pull it onto the runway, put a dolly under the left wheel, and tow it to the ramp. We then had breakfast and after eating I went to work taking the left wheel off. When I got it off, I was surprised that there was not a bad spot on the tire and it appeared normal. I put air into it to see what would happen. It was holding air except it was leaking through the valve stem. After tightening the valve stem, it held air. I reinstalled the wheel, and flew back to KEET. I went to the airport today and the tire was still holding air.

I was thinking about what happened to cause this. Several months ago I purchased a tool that came with new valve caps so I could check the tire pressure and add air with the wheel pants on. There is a hole in each wheel pant, and by inserting the tool into the hole (after aligning the value stem with the hole) you can take the valve cap off. I also bought an air chuck with a straight stem so I can add air through the hole. The tool is then used to put the cap back on.

Shortly after getting those new caps and installing them, I went to the hangar one day and the left tire was flat. I went through the procedure and added air. For several months the air pressure has remained good.

Last Thursday I decided to check the pressure in the tires and I added a couple of pounds of air to both main tires. Saturday morning I looked at all the tires and they all appeared to be normal.

After winding up in the grass and taking the wheel pant off, I realized the cap on the left valve stem was on crooked and therefore it was not tight. I realized that it had cross threaded when using the tool blind through the hole. The cap has a rubber seal in it so that when it is tight, it will seal the valve stem.

So after thinking about this entire situation, I realized that for the last several months the cap has been sealing the tire and keeping the air from escaping. When I didn't get it on tight, and flew up to 5,500 feet for the trip, the outside air pressure was lower and allowed all the air to escape and therefore I landed on a flat tire. I was fortunate that the only damage was to the wheel pant.

The moral to this story, and the reason I am sharing it, is that if you think there is a problem (tire losing pressure), there probably is. I had wondered for a few months why that tire was flat that day, and why it held air pressure for several months after I filled it. I now know, the valve stem was leaking and I did not check it. I should have investigated further and found the problem initially and before flying the aircraft.

I now have all the wheel pants off, and will have them off until I repair the left wheel pant. I like them off so I can see the whole tire and add air easily. I am wondering how much speed you really gain by having the wheel pants on.

I am going to Triple Tree this week so I will see what my cruise speed is without the wheel pants.

The people at KBGF were wonderful. The airport manager, a couple of mechanics, etc. helped get the aircraft to the ramp and then loaned me tools so I could get the aircraft flying. A friend who is an RV-12 owner and lives fairly close flew over and brought me a tire and tube, which I ended up not needing. But the friendless and helpfulness of aircraft owners, mechanics, etc, was wonderful.

I look forward to going back to the breakfast there again, and arriving in a less eventful way and getting to enjoy the breakfast and the company.

Thanks again to those people who helped me. I hope by sharing this story, my mistake, that someone will be able to avoid a similar situation.
 
I would say, at the very least, you need to replace the tube if the tire has been run flat, and depending on age, you may want to replace all three tubes. AIRSTOP tubes work very well to minimize air leakage over time. With AIRSTOP tubes I need to check air pressure only twice a year, and even at that, there is very little loss of pressure.

You have found out that differential braking is absolutely necessary for directional control on the ground. I would inspect brake linings and also make sure aluminum hydraulic brake lines on each gear leg are in good condition. I replaced my aluminum gear leg lines with braided Teflon lines from Aircraft Specialty. Might also want to check for air bubbles in crossover tubing in the cabin and bleed the brakes if necessary.
 
... I am wondering how much speed you really gain by having the wheel pants on. ...

Good info, glad it ended up turning out OK. I guess I'll add a couple of additional cautions.

My valve caps have a small circular partition that's concentric with the outer wall of the cap. I guess it's purpose must be to surround valve core and somehow protect it from I don't know what. In any case, I once had a slightly bent valve core stem in the nose wheel Schrader valve. It was bent enough so it contacted that inner wall which depressed the valve somewhat and let the air out of the tire. I'm more careful now when I put the dust caps on the valve stem.

Which brings up my second caution. That incident I mentioned above happened on my nose wheel. I would have thought that a tire with little or no air would look flat but mine didn't. As a matter of fact, at least with my nose wheel, I had no idea it was flat! I had a friend standing by to see me off and he stopped me as soon as I boarded the aircraft. The tire looked perfectly normal in the preflight and it wasn't until I added my extra weight (about 210#) that it was apparent that it was flat. Even knowing it was flat, we both looked at it with me out of the aircraft and it looked normal. The sidewalls must just be stiff enough, coupled with what was probably a small amount of air, to support the plane without flattening the tire. Anyway, part of my preflight now is to "bounce" the aircraft a bit and watch the tires - low pressure is pretty obvious when I make those movements.

fwiw, I always fly without the wheel fairings locally so I can see the tires, brakes and brake lines. I do add the fairings for trips. It takes me about 45 mins to add them and I gain about 5 kts or so.
 
Any time you add air to a tire, any kind of tire, you should wipe a bit of spit onto the valve stem. If a bubble appears, the valve stem is leaking for some reason. Never depend on the cap to hold air. The cap is simply a device to protect the valve core.
 
I had a bad valve poppet on one of my valve stems. I bought a kit at Harbor Freight that had a tool to remove the poppet and some extra poppets. A simple fix that took Ten minutes and lasted 500 hours until tire and tube change out.

I hate that a flat puts the wheel pant n the ground. I ended up removing my wheel pants to simplify maintaining tire pressure. Once more proving life is more fun with your pants off!😜
 
My RV-12 has Aero Classic Tires. I was looking at Condor tires in Aircraft Spruce catalog.

Is anyone using Condor tires? Is there a major difference between the two?

Thanks.
 
I installed Desser 500-5 6 PLY AWBS RETREAD, ELITE PREMIUM 2 GROOVE (ELITE) and have over 250 hours on them. Excellent wear. Cost was $140 for two tires with free 500-5 AERO CLASSIC **BUTYL** INNER TUBE TR-67 (GL-5067) back in March 2016. Haven’t even flipped them yet to even wear pattern. Tire is slightly larger so need to enlarge wheel pant opening to maintain 1/2” clearance all around.
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I installed Dresser 500-5 6 PLY AWBS RETREAD, ELITE PREMIUM 2 GROOVE (ELITE) and have over 250 hours on them. Excellent wear.

I have the same ones. I have more than twice as many landings and counting on my Desser Elites than I got on the original Aero Classics ...
 
It?s Desser not Dresser. You can find them online.
Your problem is in trying to inflate the tires without removing the wheel pant.
I have never had any success trying to inflate the tire through the wheel pant with those screw on extensions. You just cannot be certain you have the stem seated properly and tight. I know it?s a pain to take the pant off but you can be sure you won?t have a leak that way. Plus it?s easier to check your brake linings with a mirror if the pant is off.
 
I have the same ones. I have more than twice as many landings and counting on my Desser Elites than I got on the original Aero Classics ...

Not saying that the Elites aren't a better wearing tire but pretty much every new RV pilot (regardless of model) gets many more landings on there second set of tires (regardless of whether they replace with the same tire or not) as they did with the tires they "learned" on.
 
Not saying that the Elites aren't a better wearing tire but pretty much every new RV pilot (regardless of model) gets many more landings on there second set of tires (regardless of whether they replace with the same tire or not) as they did with the tires they "learned" on.
Yeah, probably a lot of truth there. Sure was true with my brake pads :) ...
 
Same thing 3 weeks ago

I am posting this situation to keep someone else from making the same mistake I did. I am a new owner, I bought my RV-12 in February 2018. I have been a pilot for many years, but am new to maintenance.

Saturday I flew from KEET to KBGF to attend a fly-in breakfast. I took a friend with me so we could enjoy the fly-in together.

When I landed at KBGF I could not steer the aircraft. It started going left and nothing I could do would stop it. I was able to miss a taxi light by using the left brake. The aircraft ran off the runway into the grass and did a 180 before it stopped. So we were sitting in the aircraft, facing the way we flew in, and not knowing for sure what happened. I thought the left tire had blown.

We got out of the aircraft and the left tire was flat. The aircraft has slid on the wheel pants on the runway before it exited to the left. The airport manager and a couple other people came out to see if we were OK and we were. They help me jack the aircraft up, get the wheel pant off, and then we were able to pull it onto the runway, put a dolly under the left wheel, and tow it to the ramp. We then had breakfast and after eating I went to work taking the left wheel off. When I got it off, I was surprised that there was not a bad spot on the tire and it appeared normal. I put air into it to see what would happen. It was holding air except it was leaking through the valve stem. After tightening the valve stem, it held air. I reinstalled the wheel, and flew back to KEET. I went to the airport today and the tire was still holding air.

I was thinking about what happened to cause this. Several months ago I purchased a tool that came with new valve caps so I could check the tire pressure and add air with the wheel pants on. There is a hole in each wheel pant, and by inserting the tool into the hole (after aligning the value stem with the hole) you can take the valve cap off. I also bought an air chuck with a straight stem so I can add air through the hole. The tool is then used to put the cap back on.

Shortly after getting those new caps and installing them, I went to the hangar one day and the left tire was flat. I went through the procedure and added air. For several months the air pressure has remained good.

Last Thursday I decided to check the pressure in the tires and I added a couple of pounds of air to both main tires. Saturday morning I looked at all the tires and they all appeared to be normal.

After winding up in the grass and taking the wheel pant off, I realized the cap on the left valve stem was on crooked and therefore it was not tight. I realized that it had cross threaded when using the tool blind through the hole. The cap has a rubber seal in it so that when it is tight, it will seal the valve stem.

So after thinking about this entire situation, I realized that for the last several months the cap has been sealing the tire and keeping the air from escaping. When I didn't get it on tight, and flew up to 5,500 feet for the trip, the outside air pressure was lower and allowed all the air to escape and therefore I landed on a flat tire. I was fortunate that the only damage was to the wheel pant.

The moral to this story, and the reason I am sharing it, is that if you think there is a problem (tire losing pressure), there probably is. I had wondered for a few months why that tire was flat that day, and why it held air pressure for several months after I filled it. I now know, the valve stem was leaking and I did not check it. I should have investigated further and found the problem initially and before flying the aircraft.

I now have all the wheel pants off, and will have them off until I repair the left wheel pant. I like them off so I can see the whole tire and add air easily. I am wondering how much speed you really gain by having the wheel pants on.

I am going to Triple Tree this week so I will see what my cruise speed is without the wheel pants.

The people at KBGF were wonderful. The airport manager, a couple of mechanics, etc. helped get the aircraft to the ramp and then loaned me tools so I could get the aircraft flying. A friend who is an RV-12 owner and lives fairly close flew over and brought me a tire and tube, which I ended up not needing. But the friendless and helpfulness of aircraft owners, mechanics, etc, was wonderful.

I look forward to going back to the breakfast there again, and arriving in a less eventful way and getting to enjoy the breakfast and the company.

Thanks again to those people who helped me. I hope by sharing this story, my mistake, that someone will be able to avoid a similar situation.

Pilotyoung,
I had a similar issue. I will spare you the details, but I would find the tire low, then pump it up, it would hold. I'd fly and it would go flat.
I removed it and checked the tire/tube/rim/brakes.
All fine.
This in a tube that was 3 months old. They can last years.
Repeat.
Same, then check again x 4?
I actually thought a buddy was playing a joke on me.

Finally, a leak was discovered when it was inflated way beyond spec.

Changed tube: fixed.

Yes, the Schrader valve can be a culprit. I thought the heat from heavy braking could have caused a failure in the bicycle-type valve stem (hypothesis only).

Suggestion: do not spray soapy water, actually immerse the tube in a tub after over inflating it.

Solution: Buy 2 new tubes.
I keep a spare in my aft baggage compartment just in case this happens x-country.

Happy landings,
Daddyman
 
With regard to carrying a spare I would say this: since it is a common aero tire I have always figured an FBO would have them. I try to carry only the unique parts an FBO would not have: voltage regulator, mechanical fuel pump and a couple of spark plugs.
 
The cap is not there to hold tire pressure! It is only to protect the valve!

+1

Your shrader valve is leaking and the cap with the rubber seal (a flaw of the fancy aviation caps with rubber seals - they hide a problem) was holding the air in that the shrader valve was letting out. It's like a tightly wrapped bandage keeps blood in your body. It keeps you from dying, but not optimal or a long term solution. As you concluded, the fault was not failing to get the cap on properly, but failing to notice the leaking valve.

Many issues with shrader valves are that they are not installed properly (i.e. tight enough) or have debris under the flared plastic sealing area. I beleive every new tube installed should include a check that the shrader valve is installed tight enough or verifying it is leak free with soapy water. I have found many new tubes where they were loose enough to leak. The tool is available at any auto store or home depot for $2.

Larry
 
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With regard to carrying a spare I would say this: since it is a common aero tire I have always figured an FBO would have them.

I always carry a spare tube... if not for yourself then for someone else. Twice I gave one to a pilot in need, once for Petit Jean and once enroute to Sun N Fun. Neither location had an FBO. Both times about a week later I received a new tube in the mail with a note that they will now always carry a spare tube.
 
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