Re: First flat in a looooong time

On 3/26/2025 9:54 PM, pH wrote:

On 2025-03-27, Joy Beeson <jbeeson@invalid.net.invalid> wrote:

>
Tuesday, 25 March 2025
>
On Saturday, I came out of Aldi to find my front tire flat.
>
On Monday, I walked to the Trailhouse and handed the wheel
to the mechanic with instructions to put in a new tube and
find out what had happened to the old one.
>
He showed me a crack at the base of the valve stem.   The
tube had died of old age!

 It's kind of nice to know it was not a nail, I guess.
 I think my last flat was a base of valve failure, too.
 Pureheart in Aptos
  

>
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Still haven't put the wheel back on, and I want to ride to
Mary Anne's Place tomorrow.
>
>
>
Wednesday, 26 March 2025
>
What was predicted to be a good day for riding turned out to
be a good day for hanging out laundry.  I'd hoped to dash to
Kroger for potatoes, but after hanging sheets in a cold
wind, spending half an hour dressing for a fifteen-minute
ride didn't sound like much fun.
>

Quite common.
Often caused by riding at low pressures.  The tire squirms with each revolution and creeps backward on the rim. Which is not significant to a tubeless system (although extremely low pressures also introduce extreme flexing of sidewalls and eventually shred the fabric).  With an inner tube however, the tube creeps until there's excess tube material in front of the valve, often bunched up and folded over itself. Behind the valve, the tube is stretched thin and prone to failure.
Some rim cross sections (notably but not only single-wall KinLin) have an extremely deep and narrow center section, well below the bead seat. That makes tire changing easier but the tube does not easily conform to that shape and tears at or near the valve area.
And there can be other issues such as broken rim liner, misplaced rim liner, longish spokes or sharp burrs on nipples from automated wheelbuilding, wrong type of rim liner etc.
When a valve tear is seen, check the pressure in the other tire. Most often it's low.
--
Andrew Muzi
am@yellowjersey.org
Open every day since 1 April, 1971