very slow and undetectable leak



A

autopi

Guest
i put on a new rim tape (velox cloth), tube and tire (nashbar prima)
on my wheel last week (a mavic cxp-22?). it was a tight fit, but in
the end everything seemed fine. i used the bike a couple days later,
no problems. but a couple days after that (1 week after putting in the
new tube) the thing was completely flat.

now i cannot find the source of the leak. i tried immersing it in
water to look for bubbles, i tried running it under my nose to feel
air coming out. no luck. i've inflated it to about 2x its normal
thickness, and it seems to be holding air--at least over a couple
hours anyway. nothing obvious is wrong with the tire after casual
inspection. the tube has one patch, but as far as i can tell, the
patch is not leaking.

any more hints on how to find where this tube is leaking? or any
alternate explanations for what may have happened?
 
D

datakoll

Guest
well, if the tube leaks air
and you patched it
then it's the chain.
 
B

Bill Sornson

Guest
datakoll wrote:
> well, if the tube leaks air
> and you patched it
> then it's the chain.


lol dammit
 
B

Bill Sornson

Guest
autopi wrote:
> i put on a new rim tape (velox cloth), tube and tire (nashbar prima)
> on my wheel last week (a mavic cxp-22?). it was a tight fit, but in
> the end everything seemed fine. i used the bike a couple days later,
> no problems. but a couple days after that (1 week after putting in the
> new tube) the thing was completely flat.
>
> now i cannot find the source of the leak. i tried immersing it in
> water to look for bubbles, i tried running it under my nose to feel
> air coming out. no luck. i've inflated it to about 2x its normal
> thickness, and it seems to be holding air--at least over a couple
> hours anyway. nothing obvious is wrong with the tire after casual
> inspection. the tube has one patch, but as far as i can tell, the
> patch is not leaking.
>
> any more hints on how to find where this tube is leaking? or any
> alternate explanations for what may have happened?


Try rotating the fully inflated tube next to your cheek (facial!). Often
can feel even the slightest air leak there. Also check by the valve -- move
it back and forth in case there's a slight slit that only opens up when the
valve is pushed sideways.

Otherwise, make it your spare and put in a new tube.

Bill "or hire a witchdoctor" S.
 
D

datakoll

Guest
there are patches leaking under load but not when not under load
and patches leaking not under load, leaking under load.
then there are patches leaking only during left turns, some only on
rights
some will leak once but never again
some never leak: these tubes rip open lengthwise...
GI>Specialized>equipment> tubes
spray with silicone before installing in kevlar/vectran tires and
cleanliness is next to what?
 
F

futrino

Guest

> air coming out. no luck. i've inflated it to about 2x its normal
> thickness, and it seems to be holding air--at least over a coupl
>
> any more hints on how to find where this tube is leaking? or any
> alternate explanations for what may have happened?
>

blow it up 5 times its size
 
D

datakoll

Guest
amaizing,no? riders complaining about tubes 'holding' air?
 
C

cmcanulty

Guest
Blow the dirt off the valve stem. Also buy a valve tool at an
autoparts store for around $1. Many tubes just need the valve stem
tightened to stop a very slow leak.
 
C

Camilo

Guest
On Aug 31, 7:09 am, autopi <[email protected]> wrote:
> i put on a new rim tape (velox cloth), tube and tire (nashbar prima)
> on my wheel last week (a mavic cxp-22?). it was a tight fit, but in
> the end everything seemed fine. i used the bike a couple days later,
> no problems. but a couple days after that (1 week after putting in the
> new tube) the thing was completely flat.
>
> now i cannot find the source of the leak. i tried immersing it in
> water to look for bubbles, i tried running it under my nose to feel
> air coming out. no luck. i've inflated it to about 2x its normal
> thickness, and it seems to be holding air--at least over a couple
> hours anyway. nothing obvious is wrong with the tire after casual
> inspection. the tube has one patch, but as far as i can tell, the
> patch is not leaking.
>
> any more hints on how to find where this tube is leaking? or any
> alternate explanations for what may have happened?


Aside from the other (serious) advice, I'd say: reinstall it and pump
it up to riding pressure. Check the pressure 4 hours later. If it is
still adequate for riding, then forget about it. Or buy a new tube
for $3 and forget about it. To me it's not worth a lot of time
figuring out where to patch a tube. (having had the same problem as
you).
 
On Aug 31, 10:09 am, autopi <[email protected]> wrote:
i tried immersing it in
> water to look for bubbles,


Deep enough to completely submerge an "overinflated" (stretched out)
tube? Big enough l/w to manipulate the tube? Bending it into new
shapes sometimes seems to help find those very slow pinhole leaks.
Also can take some time for enough bubbles to come out to ID an actual
hole as opposed to the air bubbles that stick to the tube when you
first submerse it. --D-y
 
V

velodancer

Guest
Sometimes a patch will leak under the high pressure when installed in
a tire, yet not leak inflated a few pounds even when it has ballooned
unrestrained. Try putting it under water again and paying particular
attention to the patch. You may be able to see a small bubble form
every few minutes. Also look at your valve. See if it leaks when not
tight (if it is a Presta). Those are the two places I look when I'm
stumped. Almost invariably it will be your patch. I once had one fail
a year later.
 
On Aug 31, 11:53 am, "Bill Sornson" <[email protected]> wrote:
> autopi wrote:
> > i put on a new rim tape (velox cloth), tube and tire (nashbar prima)
> > on my wheel last week (a mavic cxp-22?). it was a tight fit, but in
> > the end everything seemed fine. i used the bike a couple days later,
> > no problems. but a couple days after that (1 week after putting in the
> > new tube) the thing was completely flat.

>
> > now i cannot find the source of the leak. i tried immersing it in
> > water to look for bubbles, i tried running it under my nose to feel
> > air coming out. no luck. i've inflated it to about 2x its normal
> > thickness, and it seems to be holding air--at least over a couple
> > hours anyway. nothing obvious is wrong with the tire after casual
> > inspection. the tube has one patch, but as far as i can tell, the
> > patch is not leaking.

>
> > any more hints on how to find where this tube is leaking? or any
> > alternate explanations for what may have happened?

>
> Try rotating the fully inflated tube next to your cheek (facial!). Often
> can feel even the slightest air leak there. Also check by the valve -- move
> it back and forth in case there's a slight slit that only opens up when the
> valve is pushed sideways.
>
> Otherwise, make it your spare and put in a new tube.
>
> Bill "or hire a witchdoctor" S.


Good post.

- Frank Krygowski
 
D

datakoll

Guest
a larger question is! what is your patch level? I go 3 tops on a
Nashbar tube before the sides rip out using Bell patch.
I'd guess the euro feathered edge foil wrapped oval patch may go 4-5.
patch bubbles are very very small in diameter in a wee tiny stream
that may disperse before rising into view.
 
A

autopi

Guest
thanks for the advice--sounds like it's either the patch or the valve.
i know it's not worth spending a lot of time worrying about, i was
mostly just curious if there's received wisdom about this sort of
thing.