The International Cessna^® 170 Association

See what a BIG can of worms came open with one question, Farnold? I just have to laugh as I would never have guessed it either. I'm going to frame this thread as the best embodiment of the "mountain out of a molehill" concept that I have ever seen. WHEW am I tired! I vote for 34 psi in the tail as the POH calls for. If you see no adverse treadwear and the tailwheel behaves normally...your question is answered. Don't worry about all the calculus and differential equations. I find POH value for the mains at 24 psi to be just fine. At 24 psi, there is much less tendancy to bounce. Don't think I'd try 30 psi unless I were operating on grass. What I WOULD like to know is why the mains, and the tailwheel to a lesser extent, deflate rapidly? Dave has this problem, and I have it. The air just seems to seep out of all the tires at an alarming rate. I would think that aircraft tire assemblies should hold air at least as well as automotive or garden equipment tires. I might put a bottle of Green Slime sealer in each tire and see if they hold air then OK...just kidding. Any thoughts on this loss of air phenomena George? BUT WAIT...only in a short paragraph or less. After this thread my eyeballs are hanging out of my head on springs

Can't remember all of the details, but an article in LPM said that aircraft tubes and tires are made out of different materials than auto tubes and tires. Have to perform different functions such as on landing going from 0 to 65, and airplane tires do not have to hold up to 60000 freeway miles, etc. The past materials for aircraft allowed air seepage but new materials are promising to be air tight.

Well, I guess you could either claim YOUTH or SENILITY on that one WA4JR!
If you claim YOUTH....then you'll never have experienced automotive tube-type tires with wide white-walls that consistently required checking tire pressures and places that sold real gasoline (not condensed aromatic vapors preserved with phenolic resins) called "Service Stations" where slender men in uniforms greeted you at your car to take your fuel order (You want Regular? or Ethyl?), check your non-maintenance-free battery water-level, non-reservoir type radiator, fan/generator/water-pump V-belts, motor-oil level(Detergent? or non-Detergent?), and clean all your non-tempered "safety-glass" windows for free! Then as the fuel was still being dispensed they'd check your tire pressures because all natural rubber inner-tubes slowly leak air. We always paid with cash (silver certificates at that!)
Now days, tubeless tires with inner liners of synthetic material, installed in sealed "safety-rimmed" wheels have made air pressure loss such a slow process that most people never even think about tire pressures until it's time to go back to WalMart and buy another set. (Or else they're suffering from SENILITY and can't remember either example.)
Because of the split wheels common on aircraft, the tube-type tires have continued in use in this industry. (Tubless tires are used on larger aircraft which also have sealed wheels and fusible plugs that automatically deflate the tires when the brakes are overheated by these new-generation "flight-deck crewmember" graduates of flight "academies" that are hired straight into airline jobs that don't require them to know much about airmanship or anything about real aeroplanes or tire/wheel maintenance, because the operator has "outsourced" maintenance and pre-flight duties to sub-contractors.) But things have improved so much now that we don't have hot meals prepared by onboard flight-chefs and served by pretty stewardesses, and men no longer travel wearing coats or ties, and women no longer wear dresses, hats, and nylons with seams. Now our fellow travellers resemble homeless vagrants and travel wearing torn blue-jeans or cut-off shorts, flip-flops and backpacks. We also must buy seperate tickets when travelling on seperate airlines, and shop/sort through a bizarre non-refundable pricing-scheme instead of only one simple, competitively-priced ticket which all airlines accept. And we must not pay for it with cash lest we be arrested. We must identify ourselves, and pay for it, with a sharp-edged weapon known as a credit-card, and we must show up two hours in advance to be kept in a "holding pen" instead of simply walking out on the ramp and up the airstairs to sit down and relax our heads against starched-white headrest coverlets for a complimentary beverage while we watch big starting-clouds of blue smoke blown away by huge propellers.
And that's the price we pay for spark plugs that last 100K miles and cars that go twice that far, instead of being worn out at 75K like in 1959.

It's also likely that you're filling your tires with common compressed air which contains lots of random-sized molecules of various gases such as oxygen, carbon dioxide, argon, radon, helium, hydrogen, etc, etc. which due to their small size more easily escape through the molecules of rubber which make up the inner tube, as well as water vapor which expands when hot due to recent compression from your air-compressor (giving you a falsely high reading) and later contracts when sitting in the hangar giving you a deflated tire, or it's sensitive to ambient air temperature misleading your tire-pressure measurements, or it's dispensed as water droplets into the tube which take up space and don't escape as easily until later heated into vapor again. The result is a more pronounced loss of air pressure some time later. Most larger aircraft fill their tires with stable, dry nitrogen from bottles which has regular, predictable molecule size and also reduces damage from oxidation and does not cause varying pressures from moisture/water vapor. (That last can also condense and freeze into ice at altitude and cut the tire liner and also turn to steam upon landing causing rapid pressure build-up and blow the tire or fusible plug.)

Go ahead. Ask something else.

Green Slime Sealer!!! I love it!
Why hasn't my A&P told me his secret!
Thanks guys for all the chuckles!

I know it's just a joke, but be careful adding anything liquid to the tube. A small leak may be sealed up, but the stuff will corrode your wheel and end up costing a lot more than a patch on an inner tube.

If you fly out of areas that have goat heads this can cause leakage. I run enough air in my tail wheel to make it look round around 40# I have recently changed to 180 gear and this puts a little more weight on the tail Russ

I've heard of this thorny plant from others and aren't quite sure what that is. What, exactly, is a "goat head"?

For gods sake tell George quickly and very briefly what Goat heads are or he will look it up and will write one helluva long page about them!

George,a goat head is a device found on the leading edge of a goat. I guess you could claim either youth or senility on that one. I'm old enough to remember when a man could could count on every goat having a head,and you could count on the waiter at a Mexican restaurant to ask you "would you like some goat head soup with that,senor?".Nowadays,bland pre-made soups have pretty much replaced authentic goat-head soup. Men & women no longer "dress for dinner" and our fellow diners resemble homeless goats themselves...............

I retract the question.

zero.one.victor wrote:George,a goat head is a device found on the leading edge of a goat. I guess you could claim either youth or senility on that one. I'm old enough to remember when a man could could count on every goat having a head,and you could count on the waiter at a Mexican restaurant to ask you "would you like some goat head soup with that,senor?".Nowadays,bland pre-made soups have pretty much replaced authentic goat-head soup. Men & women no longer "dress for dinner" and our fellow diners resemble homeless goats themselves...............

Good One Eric!

George,

Eric is correct....rare to see goat head soup south of the border anymore...used to be served with pickled Baloot eggs and palm seed crackers....may still be available in Kandahar if they didn't blow up the resturant or shoot the chef.

I run about 26lbs in the mains (800's) and 40lbs in the tailwheel tire.
I have a flat spot worn on the tail wheel tire and need to replace it, any suggestions on the best place to buy one
Bob

Bob,I haven't seen suppliers offering flat spots for a reasonable price in a long time,but if I do I'll be sure to let you know. A used one is probably the way to go. I could be persuaded to sell you my flat spot,what'll you bid for it?

Eric

Eric...... Very funny That flat spot matches the top of my head where the hair is missing
I wonder how I got the flat spot (on the tire)
I thought that maybe my tail wheel .... wheel ski was frozen up and I wore the tire on landing, last winter.
Could I have worn it landing on asphalt in the summer
Bob