On 1/5/19 11:36 AM, Bicycle Belle Ding Ding! wrote:
Thanks, all. I still can’t understand how it happened - the kids would never touch it (they don’t care about anything other than the bike actually WORKING) and I didn’t leave it out of sight where someone else could mess with it. I don’t remember the last time I filled it, but the back tire wasn’t flat, just needed to be topped off. The valves are schrader. So weird.
Given enough time, all inflated tubes will go flat because air molecules can make their way through the rubber membrane of the tube through osmosis. But that's a long, slow process.
More mysterious are the flats that are related to issues at the valve. With Presta, the most common in my experience is separation of the valve from the tube; those can be very difficult to diagnose. You can immerse an inflated tube with a small separation at the base of the valve in a sink full of water and see no leaks until you start to tweak and flick the valve stem, at which point sometimes you can see a stream of bubbles. With a Schraeder valve, if the valve core isn't screwed down all the way there can be a very slow leak through the core. You should be able to see that holding an inflated tube under water as the air forms a bubble when escaping.
It's also possible the tube in question has a small defect that allows very small amounts of air to escape. I once bought a batch of tubes online and every one developed multiple pinhole leaks along the seam of the tube.
Bill, I have never had a front blowout but I dread spinal cord injuries and get the willies just imagining. You’ve ridden more miles than most of us, I’d guess. Curious, have you ever suffered a front flat?
I've had several. Most of the time they're slow leaks, typically glass punctures, and you don't discover them just riding along until you try to make a sharp turn, at which point there's a WHOOPS - WHAT THE HELL JUST HAPPENED? sensation as the tire rolls under (sidewall collapse).
I've also had a blowout - a cut in the sidewall just above the bead, caused by a sharp edge inside the rim. I was crossing one of the bridges across the Potomac River at the time, heard the BANG but didn't know if it was front or rear. Everything was fine as long as I was going straight - I'd heard you shouldn't brake the wheel with the blowout, but since I couldn't tell which that was I was coasting to a stop when I ran out of path at the end of the bridge and had to turn. When I tried to turn the bike lost all directional stability, rolled over and augered into the ground.
I may just replace the tube to be safe. I love the owner of the bike shop, and it’s good to give him the business.
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