Leaky left main - thoughts?

How to keep the Cessna 170 flying and airworthy.

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redacted
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Leaky left main - thoughts?

Post by redacted »

I keep track of airing up the tires to spot things like this. Tubes and tires are only a couple months old, less than 50 landings on the them. 850x6 mains, aired to 22psi. Left one was down to 13psi a week after last tire check and air up. When I moved the plane in and out of the hangar I have to pivot on that left main about 30º to get the tail in/out of the corner so other planes will fit. My theory is that I've worn the tube and it's started to leak. Would think that would cause that much wear on a new tube but 22psi is on the lower side of these tires (but perfect for the plane).

Thoughts?
Nathaniel Perlman
1952 170B
N2282D S/N 20434
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Joe Moilanen
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Re: Leaky left main - thoughts?

Post by Joe Moilanen »

I'd check the valve core first, no bubbles there and then I'd tear it down. Be liberal with talc when you install these...

Joe
4518C
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GAHorn
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Re: Leaky left main - thoughts?

Post by GAHorn »

It’s unlikely that a tube only a few months old is leaking due to age or wear. A tube that fresh is likely defective from the start.

The “standard” for inner-tubes for aircraft expired around 1960. It was an Air Force standard and the USAF quit using tube-type tires around that time so declared the standard to be “obsolete”. Aircraft Tires meet a TSO however cheap tubes of unknown quality are very common these days.

I suggest you ascertain the country of origin and if not U.S. or U.K. I’d reject them.

The inside of tires should be “dusted” liberally with tire-talc before inner tubes are installed. The tubes should be lightly inflated and then allowed to relax before final pressurizing to spec. (The 170 should have 24 psi on mains and 35 on the tailwheel (although more can be acceptable on the tailwheel up to about 45 is in the Scott mfr’r chart, IIRC.)

A newly-installed tire/tube can lose significant pressure in the first 24-48 hrs when there exists air between the tube and tire. A “bubble” of air between the tube and tire will slowly escape, therefore do not be surprised if this occurs. (It most often occurs when the tube is not lightly inflated and allowed to relax again before final pressurizing, as mentioned above.)

Running a tire LOW on pressure can ruin a tube because it increases friction as the tire/tube “squirm” against each other. Also, a low-pressure tire can slip on the wheel at touchdown and braking and this can stretch or tear the tube at the valve stem.

Hope this helps.
'53 B-model N146YS SN:25713
50th Anniversary of Flight Model. Winner-Best Original 170B, 100th Anniversary of Flight Convention.
An originality nut (mostly) for the right reasons. ;)
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redacted
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Re: Leaky left main - thoughts?

Post by redacted »

Copy all. Thanks. Built up a dozen or more wheels and tires over the years, hadn’t seen this happen. Headed to the hangar, will double check valve core, tubes are from Air Trac.

Thanks for the input, reinforce it’s not likely hanger movement. Cheers everyone.
Nathaniel Perlman
1952 170B
N2282D S/N 20434
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redacted
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Re: Leaky left main - thoughts?

Post by redacted »

UPDATE——————-

Thanks everyone. It was a leaky valve stem core. I remember now when I installed it I had to back it off of tight a turn or two so the pressure gauge would work. It must have loosened up a tiny bit more. Soapy water confirmed. Didn’t remember the valve core part until I started to tighten it, damn Covid brain strikes again. Crisis averted! Stand down.
Nathaniel Perlman
1952 170B
N2282D S/N 20434
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