Flat & Tube Patch question(s)

Returning from my road ride, I developed a slow leak in the rear tire.
I decided to pump up the tire and see how long it would last, rather
than change the tube on the side of the road. (It was getting close to
dusk and I only had 5 or 8 miles to go. I was able to ride a couple of
miles before reinflating again. Repeating a couple of times got me
home. However, the last turn home caused the tire to slip laterally on
the rim (ouch). I later replaced the tube and patched the original to
use as a spare.

While patching the tube, I found a "snake bite" where the holes were
say 2 or 3 mm apart. These were on the road-surface side of the tube 6
inches from the valve stem. I assumed the classic pinch flat snake
bite would be much farther apart, about the width of the rim.

Q1 - Is that not the case.?

While checking the inside of the tire, I could find nothing to account
for the original slow leak (assuming the snake bite was caused at the
last turn of the ride.) I inflated the tube to about 4 inches diameter
and checked the entire tube with a liquid detergent and water. I also
checked the valve. No leaks.

Q2 - Am I missing something? Will the tube likely be a reliable
spare?

Q3 - Now that the tube cement has been opened, how long before it
"dries up" and is not usable? Other cements and glues I've used always
seem to dry in the tube after opening regardless how tightly I recap
them.

Thank you.

TPO

wrote:
Returning from my road ride, I developed a slow leak in the rear tire.
I decided to pump up the tire and see how long it would last, rather
than change the tube on the side of the road. (It was getting close to
dusk and I only had 5 or 8 miles to go. I was able to ride a couple of
miles before reinflating again. Repeating a couple of times got me
home. However, the last turn home caused the tire to slip laterally on
the rim (ouch). I later replaced the tube and patched the original to
use as a spare.

While patching the tube, I found a "snake bite" where the holes were
say 2 or 3 mm apart. These were on the road-surface side of the tube 6
inches from the valve stem. I assumed the classic pinch flat snake
bite would be much farther apart, about the width of the rim.

Q1 - Is that not the case.?

No. It sounds like you're envisioning the two "bites" coming from the
two rim edges, but the usual snake-bite happens on only one side of the
tube with the tire bottoming out against a rock or hole and pinching
the upper and lower portions of the tube between the hard object and
the single rim edge on that side. The two marks on the tube can be
fairly close together and sometimes only one is actually a puncture.
It's also possible, but rare, for both edges of the rim to pinch the
tube and create four simultaneous holes.

While checking the inside of the tire, I could find nothing to account
for the original slow leak (assuming the snake bite was caused at the
last turn of the ride.) I inflated the tube to about 4 inches diameter
and checked the entire tube with a liquid detergent and water. I also
checked the valve. No leaks.

Q2 - Am I missing something? Will the tube likely be a reliable
spare?

The check described above sounds adequate as long as you rotated the
tube through the water slowly enough to be sure to spot any telltale
bubbles. In that case I'd assume the snake bite was the cause of the
original slow leak. The tube should be fine as a spare after patching
the snake bite holes.

Q3 - Now that the tube cement has been opened, how long before it
"dries up" and is not usable? Other cements and glues I've used always
seem to dry in the tube after opening regardless how tightly I recap
them.

I've had tubes of glue last for at least a couple years after being
opened, but I still carry a spare glue tube just in case. When closing
the tube I squeeze a bit of the glue onto the threads inside the cap in
the hope of forming a tight seal without needing to tighten down so
much that it cracks the plastic cap. Using this technique I find that
I always run out of patches well before I use up all the glue so I
never have a shortage of glue tubes to carry as spares.

Thanks for info.
My new question is this: My LBS sold me an innertube smaller than the
tire size I asked for (both circumference and width). When I
questioned him, he said it would be fine.

If that is the case, why bother with sizing the innertubes?
Or did I get bad advice for the sake of a small $ sale?

TPO

peter wrote:
wrote:
Returning from my road ride, I developed a slow leak in the rear tire.
I decided to pump up the tire and see how long it would last, rather
than change the tube on the side of the road. (It was getting close to
dusk and I only had 5 or 8 miles to go. I was able to ride a couple of
miles before reinflating again. Repeating a couple of times got me
home. However, the last turn home caused the tire to slip laterally on
the rim (ouch). I later replaced the tube and patched the original to
use as a spare.

While patching the tube, I found a "snake bite" where the holes were
say 2 or 3 mm apart. These were on the road-surface side of the tube 6
inches from the valve stem. I assumed the classic pinch flat snake
bite would be much farther apart, about the width of the rim.

Q1 - Is that not the case.?

No. It sounds like you're envisioning the two "bites" coming from the
two rim edges, but the usual snake-bite happens on only one side of the
tube with the tire bottoming out against a rock or hole and pinching
the upper and lower portions of the tube between the hard object and
the single rim edge on that side. The two marks on the tube can be
fairly close together and sometimes only one is actually a puncture.
It's also possible, but rare, for both edges of the rim to pinch the
tube and create four simultaneous holes.

While checking the inside of the tire, I could find nothing to account
for the original slow leak (assuming the snake bite was caused at the
last turn of the ride.) I inflated the tube to about 4 inches diameter
and checked the entire tube with a liquid detergent and water. I also
checked the valve. No leaks.

Q2 - Am I missing something? Will the tube likely be a reliable
spare?

The check described above sounds adequate as long as you rotated the
tube through the water slowly enough to be sure to spot any telltale
bubbles. In that case I'd assume the snake bite was the cause of the
original slow leak. The tube should be fine as a spare after patching
the snake bite holes.

Q3 - Now that the tube cement has been opened, how long before it
"dries up" and is not usable? Other cements and glues I've used always
seem to dry in the tube after opening regardless how tightly I recap
them.

I've had tubes of glue last for at least a couple years after being
opened, but I still carry a spare glue tube just in case. When closing
the tube I squeeze a bit of the glue onto the threads inside the cap in
the hope of forming a tight seal without needing to tighten down so
much that it cracks the plastic cap. Using this technique I find that
I always run out of patches well before I use up all the glue so I
never have a shortage of glue tubes to carry as spares.

someone writes:

Returning from my road ride, I developed a slow leak in the rear
tire. I decided to pump up the tire and see how long it would last,
rather than change the tube on the side of the road. (It was getting
close to dusk and I only had 5 or 8 miles to go. I was able to ride
a couple of miles before re-inflating again. Repeating a couple of
times got me home. However, the last turn home caused the tire to
slip laterally on the rim (ouch). I later replaced the tube and
patched the original to use as a spare.

While patching the tube, I found a "snake bite" where the holes were
say 2 or 3 mm apart. These were on the road-surface side of the
tube 6 inches from the valve stem. I assumed the classic pinch flat
snake bite would be much farther apart, about the width of the rim.

Q1 - Is that not the case.?

That is not the case. Snake bites from bottoming on a road hazard
pinch the side of the tube in a manner similar to vertically pinching
the cheek. Hole spacing is the length of tube that is contained in
that fold. When the tube is flat and in its un-inflated shape, the
distance shrinks proportionally to the ratio of flat to inflated minor
circumference. It has nothing to do with the width of the rim. The
tube never touches the rim. It lies in the fold of the tire casing.

While checking the inside of the tire, I could find nothing to
account for the original slow leak (assuming the snake bite was
caused at the last turn of the ride.) I inflated the tube to about
4 inches diameter and checked the entire tube with a liquid
detergent and water. I also checked the valve. No leaks.

If the tube was in the tire for a longer time, it bonds with the
casing and doesn't leak fast. Of course, if you put plenty of talcum
in there, you won't get a slow leak but rather a fast one. That is a
saving grace of pinch flats. They go flat slowly if the tube has been
in place for a while.

Q2 - Am I missing something? Will the tube likely be a reliable
spare?

What do you believe you are missing. If you gave it a water
submersion test, there should be no doubt. By the way, get tubes that
barely fit in the tire so they are not stretched to near bursting in
use. Weight weenies use 1/2" minor diameter tubes because they weigh
less. To make up for that, they puncture more easily and go flat in a
hurry.

Q3 - Now that the cement tube has been opened, how long before it
"dries up" and is not usable? Other cements and glues I've used
always seem to dry in the tube after opening regardless how tightly
I recap them.

Glue tubes with the cap firmly screwed down generally dry up just as
fast as ones that have never been opened because the leak is the crimp
at the bottom of the tube. Just the same, hold the glue tube
vertically squeezing out any air before replacing the cap. That gives
the volatile solvent less space into which it can evaporate and escape
when the tube is again opened.

Why so anonymous?

Jobst Brandt

Thanks for info.
My new question is this: My LBS sold me an innertube smaller than the
tire size I asked for (both circumference and width). When I
questioned him, he said it would be fine.

If that is the case, why bother with sizing the innertubes?
Or did I get bad advice for the sake of a small $ sale?

We need to know the size of the tire, as well as the tube, to correctly
answer that question. In general you can bump down maybe one size tube if
you have to, but I'd generally try to use one that has an indicated range
that includes the size of the tire in question. Do keep in mind that there
is a range of tire sizes (width) that each tube will acceptably handle. For
example, the most-common road tube size is indicated as being a 700 x
18-25c. That tube is going to work fine for either a 700c or 27" tire
(either 622 or 630mm as indicated on the sidewall), and a width of 18-25.
However, it will be a pretty snug fit in an 18c tire, especially if it's not
a "superlight" (thinner) variety. And it will stretch fine to fit up to the
25c size. I wouldn't recommend it for normal use in a 28c though, as you're
stretching the walls pretty thin and more likely to see an issue where the
valve is attached to the tube.

--Mike-- Chain Reaction Bicycles
www.ChainReactionBicycles.com

On 25 Nov 2006 19:37:19 -0800, wrote:

Returning from my road ride, I developed a slow leak in the rear tire.
I decided to pump up the tire and see how long it would last, rather
than change the tube on the side of the road. (It was getting close to
dusk and I only had 5 or 8 miles to go. I was able to ride a couple of
miles before reinflating again. Repeating a couple of times got me
home. However, the last turn home caused the tire to slip laterally on
the rim (ouch). I later replaced the tube and patched the original to
use as a spare.

While patching the tube, I found a "snake bite" where the holes were
say 2 or 3 mm apart. These were on the road-surface side of the tube 6
inches from the valve stem. I assumed the classic pinch flat snake
bite would be much farther apart, about the width of the rim.

Q1 - Is that not the case.?

Usually, no. In my experience at least, the two holes are radially
separated along the sidewall area, sometimes as close together as 8mm.
I have yet to have one happen as a result of *both* rims edges
compacting the tube to the rubture point...and if that were to take
place, I'd expect to find three or four holes, not two.

While checking the inside of the tire, I could find nothing to account
for the original slow leak (assuming the snake bite was caused at the
last turn of the ride.) I inflated the tube to about 4 inches diameter
and checked the entire tube with a liquid detergent and water. I also
checked the valve. No leaks.

Q2 - Am I missing something? Will the tube likely be a reliable
spare?

It may be that the valve core was leaking. Also, recheck the tube at
the base of the valve with slight side pressure applied in several
directions; it is not unusual for a fault at that location to remain
sealed under the low pressures present when the tube is not confined
within a tire, but deflecting the stem sideways almost always opens up
the leak.

If there's really no unpatched leak, and the patches are properly
applied, there's no reason for the tube to be unreliable.

Q3 - Now that the tube cement has been opened, how long before it
"dries up" and is not usable? Other cements and glues I've used always
seem to dry in the tube after opening regardless how tightly I recap
them.

Tubes of tire cement typically dry up almost as fast unopened as they
do after the seal is punctured; that's because the crimp at the other
end is a very poor seal. If you get 6 months of additional life from
it, consider yourself fortunate indeed.


--
Typoes are a feature, not a bug.
Some gardening required to reply via email.
Words processed in a facility that contains nuts.

While patching the tube, I found a "snake bite" where the holes were
say 2 or 3 mm apart. These were on the road-surface side of the tube 6
inches from the valve stem. I assumed the classic pinch flat snake
bite would be much farther apart, about the width of the rim.


My first (and only) road pinch flat came on a long slight downhill
grade doing about 65 km/h.
I did not recognize it as a flat, and continued home (another 2 miles
or so). I only noticed a slight noise and 'bump' every rotation of the
wheel. I elected to continue since I was so close to home (and I
*hate* slowing down when travelling at those speeds...there's something
strangely validating about keeping up with traffic). I thought it
might be a piece of gum stuck to my tire.

I got home, spun the rear tire, and found no indication of a drivetrain
problem or anything stuck to the tire. I never noticed a flat; the
tire held its shape and I was in a rush to get to work. The next day,
I discovered that the rear tire was flat.

While checking the inside of the tire, I could find nothing to account
for the original slow leak (assuming the snake bite was caused at the
last turn of the ride.) I inflated the tube to about 4 inches diameter
and checked the entire tube with a liquid detergent and water. I also
checked the valve. No leaks.

I removed the tube and found a diamond-shaped lateral hole, big enough
to push an (unsharpened) pencil through. Yowza! I was riding at speed
on that thing? Despite the size of the hole, it the tire/tube retained
enough air to get me home (and to trick me during the subsequent
"inspection").

I checked the rim for damage but couldn't find any. And my tire
(Michelin Pro Race 2) came out of the incident unscathed...no
punctures. Here's the really confusing part. My tire had been
inflated to 110+ lbs just prior to riding that day...so I can't imagine
how I got a pinch flat.


Q2 - Am I missing something? Will the tube likely be a reliable
spare?

Heh...with a hole that big, I decided to use the tube as a chainstay
protector on my MTB

On 25 Nov 2006 20:47:53 -0800, "peter" wrote:

The check described above sounds adequate as long as you rotated the
tube through the water slowly enough to be sure to spot any telltale
bubbles. In that case I'd assume the snake bite was the cause of the
original slow leak. The tube should be fine as a spare after patching
the snake bite holes.

So far (tempting the p*nct*r* fairy), the only snake-bite flat I've
had was NOT a slow leak. Hit the rough pavement (the mayor STILL
hasn't fixed that spot!), and I was flat within 50-75 feet.

Pat

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