A Riddle of a Tire

Riddle me this my people.

I have been fighting a slow leak on my front tire for about a year-and-a-half.

My first though was that the o-ring on the air-pressure-gauge stem cap degraded, so I removed it.

The leak persisted; losing 10-15 PSI overnight.

I pulled the wheel and did the soapy water test. No evidence of a leak, but the leak persisted

I broke the bead, cleaned the tire and the rim, reseated it using the best tire lube I know of. The leak persisted

I Did the soapy water test again. This time I made sure that the wheel and valve stem got involved in the party. No sign of a leak.

The tire being fairly new (less than 2,000 miles on it), I stared topping up the tire before every ride. I did that for over a year.

I added Ride-on tire sealant ( I hate tire sealants) about a year ago (give or take a few months). The leak persisted.

About a month before my vacation trip I reinstalled the air-pressure monitoring valve cap just to have a quick reference as to the tire pressure. I replaced the o-ring for the cap [EDIT; I honestly am not sure if I replaced the ring or not, but I do remember removing it for inspection]. The leak persisted.

My last ride before vacation was three weeks ago. I topped the tire off as usual, and parked my baby after the ride.

I went for a ride this evening. The first in three weeks. On my pre-ride inspection the cap showed dead-nuts-on 28 PSI. My air gauge agreed.

I think that I know what occurred to finally stop the leak. I did nothing that has not been covered above.
What do you think happened?

 

Your neighbour is not home from work yet?

 

Neighbor has an entire garage full of black market, slightly compressed air that he is selling on the side.

My best guess is a tiny hole in the rubber that leaks only when the sidewall is compressed a bit, depending on how its parked. But that's a baffling one.

 

The Ride-On finally got to the spot.
Or, you have a porous rim.

 

The neighbor works at home. IT job. The lucky sob.

 

Maybe on the sealant, but it's been a good 8 months.
The wheel is the same one that the bike came with 40 odd years ago.

 

I have heard about stress fractures in sleeves in trucks that are impossible to find without the right amount of stress or x-raying.
I wonder if it's something like that in the wheel?

 

Maybe, except....

[Edit] I truly appreciate that comment. The roads here get torn to bits every winter. The village that my daughter lives in has the reputation of being nothing but potholes (and it's not an unfounded reputation).

 

I appreciate the comments. I find this sort of questioning and response to be a crucial part of maintaining a solid perspective about troubleshooting and problem solving,

My thought on the matter:
In the weeks before the vacation trip my Jeep was laid up to complete some projects that got put off for the last two years (mainly fixing the sunroof and getting the transfer case to shift again).
The Seca was my main transport during that time, and I neglected checking air pressure every day (though it was checked during that time).
One of the things I've been battling since putting this front tire on is a very slight shimmy above 45 MPH. It static balances fine, but the shimmy never fully went away (hands on the bars are enough to dampen it fully, and since the vast majority of my riding is urban now it wasn't a priority).
I figure that the combination of hot days, somewhat spirited riding, and air pressure being about 5 PSI low allowed the tire to finally seat properly. The shimmy is gone, and I should have mentioned that before.

Word to the wisest of all of us: systems that rely on other systems, that rely on clear-thinking to function properly can sometimes kick your backside before you figure out the underlying problem.
I'm still not certain that I've figured it out, but I'm happy again for now.

 

As of today I still haven't had to air-up the front tire. She's back to being my main transportation as of tomorrow, and until I get the alternator changed on my wife's vehicle. So for about a week.

 

all this riding and you'll soon have to change the tyre anyway

 

I do hope so. The rear is almost done. I'm a descendant of Scots and Norwegians. Every penny counts.
A new set of shoes will go on by next Spring, even though it pains me to replace the front since it still has 60% of the tread.