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From: AMuzi <am@yellowjersey.org>
Newsgroups: rec.bicycles.tech
Subject: Re: First flat in a looooong time
Date: Thu, 27 Mar 2025 07:33:23 -0500
Organization: Yellow Jersey, Ltd.
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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
> 
> 
> 
>>
>> --------------------
>>
>> 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