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Flat tire question

Charles in SC

Well Known Member
I have read here over the years about folks having to deal with flats and some carry the tools and spare to change them. My question is what causes the flats? Debris on the ramps/runways, improperly installed tires, tubes etc? I am asking this because I am just getting my -7 going and in over 40 years of being around aviation I have not ever had a flat but the ones I have seen were mostly due to pinched tubes and improperly inflated tires. Maybe I have just been lucky.
Thanks in advance!
 
I’ve had a flat on a Cessna that I delivered once.. the valve stem was so dry rotted, that it fell off and rubber crumbled by hand. The previous owner said that the other side went flat just like that, but he only changed the one side. I would say maintenance is probably a big cause.. under inflation along with hard landings, or more probably side load landings are a big factor.
 
The last two flats I had were caused by air leaking past the filler valve in the stem. One I just tightened and the other I replaced the valve.
So I carry a stem valve tool and extra valve in my go toolbox.
 
Low tire pressure combined with heavy braking can cause the tire/ tube assy to rotate and tear or shear the tube stem. Keep the hangar floor and ramp clean, especially those little pieces of safety wire.
 
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Three Flats

I’ve experienced three flats in my RV7A. One just as I was buying it, another taxing to the runway, and the third pulling it out of the hangar. I would say two of these flats were do to poor maintenance practices and one was due to extreme temperature change. In all three cases the “low tire” did not look visibly flat at first glance.

IMHO tires on the RV, because of their small size, tend to appear normal looking when air pressure is as low as 20 lbs. I now check all tire pressures at least quarterly and always after a significant change in the weather (major temperature drop). Haven’t experienced one tire problem since instituting this practice.
 
It seems an E-Lift wards off most danger of a flat :).
https://vansairforce.net/community/showthread.php?t=184578

The goal should be not to get a flat in the first place :D
Good tires (Michelin/Goodyear), properly installed with Michelin Air stop tubes, air pressure >35 psi will eliminate 99% of flats.
Every flat I've ever fixed (many) would not have happened if the above was religiously followed.
Stop being lazy and check the air pressure at least every 90 days.
 
I've heard a lot about how time-consuming it is to check tire pressure on the RV-10. Big wheel pants, lots of screws, etc, etc. With appropriately-located holes in the pants and brackets, it takes about 5 second per wheel to check the tire pressure, and only slightly longer to add air if needed.

Pants stay on unless you just have to have a look at other things while you're there.
 
Bill- What tubes are you running on your mains?? I’m guessing they have the straight stems?
 
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I've never had a flat (knock on wood) in 1600+ hrs on my RV-6 and I've landed on some rough places. Though I can't say I've been to any that were littered with goat heads :confused:
Michelin Air Stop tubes, Condor tires. I always replace the tubes when changing tires although I'm reconsidering that based on some other threads on the topic. I don't have those links but the gist is, ample evidence that if cared for properly and inspected for chafing / wear good tubes should last through many tire changes.
 
I would say:

1.) Low tire pressures allowing scrubbing tire casing on inner tubes and even shearing valve stems in extreme cases. I like to keep mains at 50psi minimum and while on the high side that works great. As a diametrically opposed aside, I keep my 31" Alaska Bushwheels on my Husky at 6 PSI. But they are tubeless and the valve stems are built into the side walls and cannot be sheared.

2.) Pinching tubes during installation. Use lots of talc powder (real talcum only). I rub it inside the tire casing and all over the tube. Then after inserting the tube into tire I remove valve stem and inflate tube a couple to times lightly to round it out and give it form. With valve stem removed the pressure inside the tube will be equal to ambient pressure. Don't re-install the stem until the wheel is completely assembled. This process keeps the tube from being pinched by the wheel halves.

3.) Avoid Leak Guard brand Butyl tubes as we have seen them come apart easily at the mold line seams around the tube. Especially if combined with too low operating pressure as mentioned in (1) above. To give them credit, they don't leak as advertised. They just pop all at once. If you do use Leak Guards use more talc powder than usual during installation and run on the high side of pressures. The extra talc will help mitigate scrubbing of the mold lines on the inside of the tire casing. Michelin Air Stops also made out of Butyl don't seem to have this same problem as the Leak Guards.

4.) I live in goat head central, but I have only had goat heads flatten the smooth tundra type tires Desser sells where they grind off the tread so they look cool (smooth). There is so little thickness left on the tire a single goat head will take them down. Not a good attribute for a tire advertised for off-airport use and they now occupy a shelf in the hangar. But I haven't seen goat heads cause flats in the typical 5.00 size tires on RV's...... Yet.
 
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The goal should be not to get a flat in the first place :D
Good tires (Michelin/Goodyear), properly installed with Michelin Air stop tubes, air pressure >35 psi will eliminate 99% of flats.
Every flat I've ever fixed (many) would not have happened if the above was religiously followed.
Stop being lazy and check the air pressure at least every 90 days.

I agree. I keep my Goodyear/Michelin tires inflated to 50 psi. I check tire pressure every month or two.

Had a flat near the south end of the taxiway here at Durango. Took 3 hrs in the hot sun to get my plane back to the ramp. Some airports have next to zero GA services. Started taking my tires reeeeel seriously after that.
 
I thought I was smart carrying a tube repair kit in the plane until I realized that I need two ratchets, sockets and extensions to split the cleveland wheel. Now carry two vice grips so that a field tube repair is possible, albeit unpleasant to get the nuts off.

Larry
 
Also pay attention to those caps. They have an o-ring that helps in case the valve stem core fails and starts leaking. I've seen it happen: valve core failed and no cap (or maybe bad o-ring - I can't remember for sure) resulting in RV sitting on the runway backing up the airliners... not a good day for that guy!
 
flats?? you name it

I have seen anything from a 7/16" open/box end wrench through a 14 ply truck tire to a wicked 3" long piece of metal through an airplane tire.
You name it and it will flatten a tire.
On the carrier you/everybody had to walk the deck anytime anybody thought there might be debris on there.
It just happens.
Art
 
Likely stupid question, but

Is there a reason not to use the gooey stuff (like NoTubes Tire Sealant) that stops smaller leaks into the tube? I know the guys with those big back country wheels use it. I think those big tires are tubeless though. Not sure if that makes a difference.
Thanks.
Johan
 
I would be concerned about wheel balance. It may work fine but on wheels that typically spin up faster than those large tires it might be a problem.
 
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