how slow do they get?

[mig]

two weeks ago i spotted that the rear wheel of my work bike had a visit. hey ho - the first for many a long year. decided to use up a new tube and fix the old one later.

swapped it out, pumped it up and hey presto, back on the road.

the problem with the old tube was less easy to find so inflated it to about 35psi and left it hanging in the shed. two weeks later it has lost pressure but not so much! have never had anything nearly as slow as that....is this a record?

[Jdsk]

Hole or valve?

Jonathan

[mig]

dunno..!! haven't properly investigated as yet.

[Jdsk]

Thanks

Jonathan

[axel_knutt]

Given that 'unpunctured' tyres still go flat eventually, it begs a definition of what constitutes a puncture.

[Mike Sales]

This may well be a very slow puncture.
If you want to find it, whether to repair or help locate whatever made it still in the tyre, this is my method.
Inflate the tube until it starts to bulge in parts. Dunk it in a large sink of water. Examine it in sections by bunching up the rest and squeezing the section under scrutiny under water and watching. Watch for some time: the puncture may be very small, only releasing a small bubble at intervals. Tiny bubbles may cling to the rubber so wipe any off and wait to see whether they reappear. Repeat carefully for each piece of the tube. If it is a valve leak this will show too. Be patient.
Don't forget to mark the source of bubbles, and use it to locate any sharps in the tyre.
If you are less frugal than me you may well fit a new tube, but it is well worth trying to find the cause, or you may well be let down on future rides.

[Mike Sales]

My grandfather ran a bike shop (it got him out of the pit).
I remember his first test on a flat, Woods valve tyre was to deposit a gob of saliva on the valve opening. A leaking rubber would be betrayed by a bubble.

[Brucey]

Mikes method is fine but if you can add a little soap to the water the bubbles will linger. If the inflated tube can stay submerged (via weights and/or clever use of grille/netting) for five minutes even a very slow leak will betray itself via a stream of bubbles in the soapy water. If you are feeling a bit impatient, you can inflate the tube inside a tyre at high pressure. Any leak is usually fairly obvious at higher pressures, simply by immersing the tyre in water, one length at a time, This hardly ever fails, although the exact point the air appears to be coming out of the tyre may not coincide with the hole in the inner tube.

Incidentally, I have had tubes which have kept me guessing; if a patch lifts or the valve starts to come out of the tube, most of the air can be lost very quickly, but the hole can then reseal itself leaving no sign.

[Galactic]

My grandfather ran a bike shop (it got him out of the pit).
I remember his first test on a flat, Woods valve tyre was to deposit a gob of saliva on the valve opening. A leaking rubber would be betrayed by a bubble.

I appreciate the OP didn't say which valve his inner tube has, but I am triggered by the very thought of a Woods/Dunlop/Blitz valve. They seem to regularly develop slow leaks that are practically impossible to source or prevent. Now any inner tubes with that kind of valve get no second chances from me. Whip 'em out and replace with a tube sporting a 'proper' French/Presta/Sclaverand valve.

(And why do the damn things keep turning up on my fleet? I'm plagued by them. Whenever I rescue a bike from the skip it seems to be fitted with them. My partner also seems to enjoy bringing Dunlop-valved inner tubes home, triumphantly showing me that she too is capable of procuring spare parts for the bikes.)

[Brucey]

arguably, the main problem with the woods/dunlop valve is that it usually makes for a tube with too many potential leak paths. There is still a factory (in India I think) churning out such tubes with clamp-in valve stems. Needless to say, they don't always do the nut up tightly enough, so an LBS close to me was able to buy 'bargain' tubes which were mostly fine if you don't mind retightening the nut a bit.

[mig]

My grandfather ran a bike shop (it got him out of the pit).
I remember his first test on a flat, Woods valve tyre was to deposit a gob of saliva on the valve opening. A leaking rubber would be betrayed by a bubble.

I appreciate the OP didn't say which valve his inner tube has, but I am triggered by the very thought of a Woods/Dunlop/Blitz valve. They seem to regularly develop slow leaks that are practically impossible to source or prevent. Now any inner tubes with that kind of valve get no second chances from me. Whip 'em out and replace with a tube sporting a 'proper' French/Presta/Sclaverand valve.

(And why do the damn things keep turning up on my fleet? I'm plagued by them. Whenever I rescue a bike from the skip it seems to be fitted with them. My partner also seems to enjoy bringing Dunlop-valved inner tubes home, triumphantly showing me that she too is capable of procuring spare parts for the bikes.)

it's a presta valve and the thing is still holding some air........

[531colin]

it's a presta valve and the thing is still holding some air........

Isn’t there a local bike recycling charity or somebody you ride with that you could give it to?

[mjr]

I appreciate the OP didn't say which valve his inner tube has, but I am triggered by the very thought of a Woods/Dunlop/Blitz valve. They seem to regularly develop slow leaks that are practically impossible to source or prevent. Now any inner tubes with that kind of valve get no second chances from me. Whip 'em out and replace with a tube sporting a 'proper' French/Presta/Sclaverand valve.

You're doing it wrong somehow. Woods are the only true cycle tyre valve in widespread use. All others let air out along the same path it entered, which isn't really a valve: "an automatic device allowing movement in one direction only".

Avoid the rubber pipe ones IMO. I was surprised some are still sold, branded Giant.

[plancashire]

Schwalbe Presta valves have a screw-in core. The threads below the locknut have a small flat, I think 4mm. This core comes undone from friction with the locknut. The leak can be devilishly slow.

I don't buy Schwalbe tubes now, partly for this reason.

Woods/Dunlop/Blitz are the devil's work. Fitting them takes longer as you have to remove the valve to push the stem through the rim, screw back in, then partly inflate. People keep unscrewing the retaining ring accidentally so it leaks slowly.

[mjr]

Woods/Dunlop/Blitz are the devil's work. Fitting them takes longer as you have to remove the valve to push the stem through the rim, screw back in, then partly inflate. People keep unscrewing the retaining ring accidentally so it leaks slowly.

How do people accidentally unscrew that? There's no need to touch it in normal use.

It's slightly fiddlier to fit but I've good tyres and generally repair what few punctures remain without removing the whole tube, so that doesn't negate the benefits of a real valve that holds air for weeks between small top ups, for me. YMMV, especially if you're the sort who rips the wheel and tube out for the tiniest pin prick.