Author Topic: Bending valve cores...  (Read 462 times)

Bending valve cores...
« on: July 06, 2020, 09:19:50 am »
How do I manage to bend the ends of so many valve cores on inner tubes?  New tube in two weeks ago and it's already at '20 degrees', as many others.  Probably something I'm doing with the pump, but don't know what.  Best way to straighten, without breaking?
Destroying rainforest for economic gain is like burning a Renaissance painting to cook a meal.  EOW.

PaulF

  • "World's Scariest Barman"
  • It's only impossible if you stop to think about it
Re: Bending valve cores...
« Reply #1 on: July 06, 2020, 09:35:01 am »
What sort of pump are you using? One with a hose or are you clamping the barrel on to the valve? If the latter I’ve found it more likely to be the cause.


I’ve had success gently bending them straight with some pliers.

Re: Bending valve cores...
« Reply #2 on: July 06, 2020, 09:45:51 am »
Thanks Paul,  generally track pump & clamp/sometimes Zefal HPx. 
Destroying rainforest for economic gain is like burning a Renaissance painting to cook a meal.  EOW.

Re: Bending valve cores...
« Reply #3 on: July 06, 2020, 10:09:32 am »
I've managed to do this by being cack-handed with my HPX; OTOH, the tubes I've done this to seem to have been fine for years in this state <touch wood> - I just have to be a bit careful unscrewing the locknuts.

Re: Bending valve cores...
« Reply #4 on: July 06, 2020, 12:31:44 pm »
probably being clumsy with the pump is causing it, but if you don't use a dustcap on the valve, it might be occurring at other times (cleaning, using a lock etc).

If you are doing it when using a Zefal HPX then you are probably in danger of tearing the valve out of the tube or other horrors. If your technique is that poor then should you attempt to use a pump with no check valve in the head (like an old Silca frame fit) you will be in danger of 'firing' the plunger out of the pump when you jam the valve open by twisting the head of the pump.  It can go about a hundred yards or so. Not recommended.

FWIW the threaded parts in the valve stem locknut are usually made of brass; they sometimes break when you try and straighten them, so this is something to try at home, not by the side of the road.

cheers

Re: Bending valve cores...
« Reply #5 on: July 08, 2020, 01:51:28 pm »
It’s very easy to do. If you’re not making sure that the head of the pump is being lifted off straight, the tiny little valve screws on a presta valve stand no chance. I tend to make sure the head is supported with my left hand whilst pulling it away with my right hand. I always position the valve at the top of the rotation, before I remove the pump head as well, and pull straight down, rather than with the valve at the bottom, or ( even worse ) at either side.
Loving life with a beautiful Bianchi.

Re: Bending valve cores...
« Reply #6 on: July 10, 2020, 08:31:09 am »
Yes, I often do it too.

Replacement valve cores are available at little cost; I seem to have to replace mine every now and then.  And when I swap out an old tube, I always keep the valve core, if it unscrews (some do, some don't), to add to my stock.

Re: Bending valve cores...
« Reply #7 on: July 10, 2020, 10:10:51 am »
And some pump heads can grab a slightly bent valve wire and unscrew the valve as you unscrew the head, very annoying and one of the reasons I have long ago modified all my wheels to use Schrader tubes and no more problems

Re: Bending valve cores...
« Reply #8 on: July 10, 2020, 10:20:45 am »
I find the problem is alleviated, if not entirely solved, by unscrewing the valve only just enough to allow inflation.  The less brass thread is showing, the less vulnerable it is to bending.