The case of the mysterious un-punctured puncture

On Monday, July 3, 2017 at 12:41:34 PM UTC-7, Mark J. wrote:
On 6/24/2017 1:12 PM, Mark J. wrote:
On 6/24/2017 11:58 AM, AMuzi wrote:
On 6/24/2017 1:04 PM, Mark J. wrote:
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.

Could be just a very small puncture, which will bleed faster at higher
pressures.

Yes, but when I reinflated back to 100 psi, the hissing didn't return.
-Mark\

Sigh. Trust Muzi, he was right. Turns out I had a ~1mm casing cut.
Next ride, the latex tube (again) /slowly/ bulged out 10 miles into the
ride and blew, then seemingly re-sealed at around 40-60 psi. Stuck a
Rema patch over the casing cut, but haven't road-tested it yet.

Mark J.

Superglue, if you get the ends to meet. I've fixed about a zillion pretty deep slices/cuts, over the years (and helped keep a ton of others' tires from going to the landfill prematurely).
I have yet to see one of my glued fixes come unglued, even on 100-115 tires, the glue is pretty darn tenacious with rubber, apparently.
Sometimes I've had success gluing a boot in like this, but the inside of the tire has that release junk on it, so I would say the rate on those is pretty darn low.