Phantom flat

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Mick F
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i an only guess

Postby Mick F » 26 Jan 2020, 2:59pm

Spot on Phil.

By leaving the bike for a week or two, and then inflating the tyres .............. because air eventually comes out of a tyre/tube .................. one needs to put more in there. It's a constant thing to do.

It must have been me putting air in that disturbed the valve seal.
Had I not done it, the front tyre would have been fine .............. though lowish pressure .............. would that have been a problem?
The rear one was fine after topping up of course.

Why one was an issue and the other one wasn't, I can only guess.
Mick F. Cornwall

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foxyrider
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Re: Phantom flat

Postby foxyrider » 26 Jan 2020, 8:01pm

rjb wrote:I always check the valve core is done up tight. Who else has gone to pump up their tyre and removed the dust cap with the valve core stuck inside it. :oops:

*1 - just last week :D
Convention? what's that then?
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Brucey
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Re: Phantom flat

Postby Brucey » 28 Jan 2020, 2:45pm

Mick F wrote:
As for getting slime in there, why do other inner tubes not have removable cores?


because they add cost and (as you have found) are another source of unreliability. Obviously if you break the top off the non-removable type of valve you are stuck (although I have repaired a tube that was bad in this way) and if you want to use sealant you shouldn't choose that type of tube either.

However IMHO if you are not planning to use sealant, and you have one of those (IMHO daft) pumps that screw onto the valve stem, you are just asking for trouble by using tubes with removable cores.

cheers
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Mick F
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Re: Phantom flat

Postby Mick F » 28 Jan 2020, 2:58pm

We've had discussions about this before. :wink:

I had a track pump with a Topeak Twinhead connector.

Remove the valve cap, unscrew the Presta thingy, connect your Twinhead.
By connecting, you release air pressure.
Pump the tyre to the correct pressure.
Disconnect your Twinhead.
By releasing, you release air pressure.

Experiment.
Connect the Twinhead and measure the pressure by equalising the pump. Note the pressure.
Remove the Twinhead.
Connect the Twinhead and measure the pressure by equalising the pump. Note the pressure. Also note that it is now less than it was.
Repeat a few times, and your tyre will be soft.

Use a Lezyne Air Bleed connector, and there is no issue whatsoever.
Schwalbe removable valve cores?

Only had one problem, and that was the other day.
Mick F. Cornwall

philvantwo
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Re: Phantom flat

Postby philvantwo » 28 Jan 2020, 3:36pm

Can you run through that again please Mick F?
:lol: :lol: :lol:
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Mick F
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Re: Phantom flat

Postby Mick F » 28 Jan 2020, 4:13pm

Sorry, I'm being too specific as it's a hobby horse of mine. :D

When one connects a pump to a Presta, some air is released.
When one disconnects, some air is released.
Topeak Twinhead was the worst IME.

Some connectors are worse than others, and some don't release air at all.
My Lezyne Air Bleed is perfect. It only releases the air in the hose, but not the tyre.

https://ride.lezyne.com/products/1-flip-std-v312
Mick F. Cornwall

philvantwo
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Re: Phantom flat

Postby philvantwo » 28 Jan 2020, 4:43pm

But Mick F.......
That air is free....
It's not costing you anything!!
:roll:
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Mick F
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Re: Phantom flat

Postby Mick F » 28 Jan 2020, 7:26pm

It's costing pumping.

It always concerned me that every single time I connected up, I had to pump the tyre.
I bought a pressure gauge to see what was going on. The gauge told the truth, but connecting the track pump with the Topeak Twinhead showed that each time a connection then a disconnection lost pressure.

Basically, a Topeak Twinhead needs a couple of pumps per connection, and then when you actually do get your tyre to the correct pressure, you remove the pump, but your pressure has reduced due to the loss of pressure on disconnection!
The pressure gauge told the truth.
Mick F. Cornwall

Brucey
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Re: Phantom flat

Postby Brucey » 29 Jan 2020, 2:10pm

Mick F wrote:We've had discussions about this before. :wink:

I had a track pump with a Topeak Twinhead connector.

Remove the valve cap, unscrew the Presta thingy, connect your Twinhead.
By connecting, you release air pressure....
.


not with either of the twinhead chucks that I have owned, unless you pushed it on too far.

cheers
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Mick F
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Re: Phantom flat

Postby Mick F » 29 Jan 2020, 4:40pm

As I said, we've had this discussion before! :D

I had to put it on far enough to stand 120psi on a Presta valve.
Putting it on to where it "should" be, it would blow off. It wasn't man enough for the job at all.

Please believe me.
I know what I'm talking about.

I tried new Topeak rubber seals. Same problem.
It took me quite some time to see what the problem actually was.

.............. but we've had this discussion before.
Mick F. Cornwall

philvantwo
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Re: Phantom flat

Postby philvantwo » 29 Jan 2020, 6:15pm

I've been using a Joeblow pump for a few years now, never had an issue with it. You're not using it correctly Mick F!
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andrew_s
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Re: Phantom flat

Postby andrew_s » 29 Jan 2020, 11:18pm

Mick F wrote:When one disconnects, some air is released.

The air in the hose is pressurised to the same pressure as the air in the tyre, and expands out through the connector as you remove it.

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Mick F
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Re: Phantom flat

Postby Mick F » 30 Jan 2020, 9:06am

Believe me, I know what I'm talking about.
What I am saying is fact.

The Topeak Twinhead needs to be pushed on further than designed onto the Presta valves in order to get the tyre to 120psi. If it's put onto the correct position, it blows off as the pressure is increased from the pump. This is despite fitting brand new seals.

Below 100psi it would be absolutely fine, I have no doubt whatsoever.

By pushing it on further than designed, the Presta valve is depressed physically by the inner workings of the Twinhead.
Consequently, the air pressure in the tyre goes UP the tube to the pump, some air from the tyre is lost into the hose at full pressure.
The hose on track pumps are rubber and mine is over four feet long.

Other pump heads work better I have no doubt.

My screw-on Lezyne is perfect. All it needs is to make sure the removable valve cores are tight ........... like mine obviously wasn't tight enough. It didn't stop me riding, and it took HOURS to loose pressure.
Mick F. Cornwall

philvantwo
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Re: Phantom flat

Postby philvantwo » 30 Jan 2020, 9:20am

Well mine has a yellow lever that locks it onto the valve so it never comes off. Before that I had a Silca track pump, used it for time trialling from when I was 16 until I was 50 when I packed it in! (I'm 58 this year) Had to hold that one on the valve.
The noise it makes is the air being released from the hose!
You're wrong mick f.
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Mick F
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Re: Phantom flat

Postby Mick F » 30 Jan 2020, 10:45am

The lever locks it on ............ but not tight enough to withstand 120psi. Fact.

The lever is also used to seal off the other end.
Presta or Schrader.

https://www.topeak.com/global/en/produc ... 2-twinhead

Notice they've got a different head for the 160psi pumps.
https://www.topeak.com/global/en/produc ... rt-digital
Mick F. Cornwall