Mark J.
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So, yesterday I was riding and heard the familiar
fwisssh-fwisssh-fwisssh of a puncture.
Veloflex Master 700x25 tire, unpatched Vittoria latex tube, originally
at 105 psi.
In the first few seconds, expecting the tire to bottom out immediately,
I looked down to see if it was the front or rear tire. Couldn't tell.
Stopped and examined the tires. Snapping a finger against the tire
showed the rear was a bit soft (lower frequency "ping" than front when
snapped), but definitely not flat.
"Fwisssh" is greatly reduced, but still slightly audible.
There is ***NO*** sealant in my tubes - unless Vittoria puts some in
without advertising, and it's undetectable when mounting.
Remounted and rode another several hundred feet to some shade (around
90F and sunny), assuming I'd need to change the tube. Rear tire is
/not/ sagging visibly; I have tan sidewalls, which makes sag easier to
see. In the shade, examine rear for protruding wire/tack/stone/glass,
see the tiniest bit of glass, but the tire is still mostly firm. Pick
out glass with Swiss army knife, it was so small and shallow, might not
have been the cause.
Then I do something I *never* do - top off the tire with frame pump.
This should have been futile - I was ~8 miles from home, but I thought
I'd see where it went. Pump's built-in gauge starts at ~60 psi, I top
it up to ~100 psi, head home. Weeks ago I had removed the inflator from
my bike bag, and it was really hot, so I appreciated not needing to do
the entire tube replacement and slow inflation with mini-pump.
On the way home, looking at the tire periodically, I see no sag.
Intentionally going over small bumps/rough pavement, front and rear feel
similar. Get all the way home. Gauge says tire is now ~50, but it
feels much firmer than that.
Next day, tire is flat as expected (and latex tubes leak a bit anyway).
Dismount tire, find generic pinhole in tube, matching tiny hole in tire.
Can't remember if this is where the glass was; there are 5-6 *tiny*
holes/blemishes in tire tread, the kind that often don't result in a
flat. The pinhole is *NOT* a *slow* leak; I've patched plenty of slow
leaks that require immersion to locate. This one shows up audibly right
away.
The mystery - on the road, the flat behaved as I would expect a tire
with sealant to behave. Fast, highly audible leak that should have had
me quickly riding on the rim slowly diminishes and stops at about 60
psi, or at least changes to a very slow leak. At home while patching,
the hole was clean and unclogged - no signs of sealant (and I'm 99% sure
there never was any.) (My entire experience with sealant is reading
about it, I've never used any).
Tube could have stuck to the tire casing and sealed somehow (I think
Jobst once speculated on this), but I talc liberally, and the tube
definitely didn't stick to the tire when dismounting.
Other details: Front tire is at 70 psi today, down from 90 yesterday,
that's normal latex leakage. I weigh about 170 lbs. Road debris around
here is mostly bearing-sized gravel from pavement deterioration, with
some larger bits mixed in.
What happened? Benevolent Gremlins?
Mark J.