Originally Posted by
Blightybiker
Hello all,
I hope you are all keeping well in this newly changed World.
Here is a short story of a small cycling misadventure:
Yesterday I thought I would go out for a spin on my Raleigh Grand Prix. As ever, I pumped up the tubes, to get the best out of the ride. On the rear tube, as I approached what I would consider the right pressure I heard the dreaded hissing of escaping air. I faffed around for a bit, cursing throughout, before removing the rear wheel and tyre. The tube, a Sunlite 700 x 20-25, 27 x1", did not owe me anything: I have been using it and its front wheel twin, for about 8 years. The air was escaping from a small tear at the base of the valve stem, where it's glued to the tube itself. I think the small waggling around of the valve stem that happens when I use my Zefal pump had fatigued that point in the tube. The valve is a Schraeder and there is no lock nut on the valve stem. (On the Michelin tubes I used many decades ago there was a lock nut. This makes the stem position more stable.)
My wheels are 27" and have chromium-plated Sturmey Archer rims. The tyre is a 27" x 1/4" Kenda. So it seems that the failed tube was the wrong size anyway.
I have just ordered a pair Of Continental tubes, of the correct size this time. Because I wanted, for an obvious reason, to have a locknut on the valve stem I was compelled to order a tube with a Presta valve: the tubes with Schraeder valves did not have a lock nut. I also ordered a couple of Presta-to-Schraeder adapters, to give me more flexibility when needing to inflate my tyres.
Have a I made a sensible purchase? I see on the Sheldon Brown website that Presta valves are not as robust as Schraeders but they are easier to inflate.
Sheldon Brown
Consider that the seeming "stabilization" of the valve stem from the locknut can only occur to the extent that the nut exerts a push/pull on the rim/stem respectively.
So the nut is just applying tension on the valve stem, resisted only by the rubber attached at it's base.
Do we really want this to occur, or is it better to stabilize the pump head against an immovable object while pumping?
I've used the rear corner of a bike's saddle as a pump head rest, which worked well. The bike was of course laying on it's side.
And I've used a protruding corner of a curb to rest the pumphead on. A rock or stump is also good.
Another approach is to pump with the valve stem pointing down, so that the detached wheel is not constrained so as to exert resisting force to the motion being fed into the valve stem by the pump. So only the inertia of the rim and tire exerts any lateral force at all.
Best of all might be to use a hose or a C02 cartridge, though I carry neither.
Shraeder valve stems are really tough, so why not stick with them and use a pump that is compatible?
And beware how a rim adapter might exert resisting force against air pressure at the base of the valve, possibly trying to peel the tube from the stem. A steel rim isn't going to be able to support the valve stem because it has no depth to it where the hole is, and it can't even support an adapter against much in the way of tilting unless it's a tight fit.
Lastly, a Presta valve in a Shraeder-sized hole may expose the tube and cause dry-rot over time, especially where smoggy air exists.
You can shield the tube there while also protecting it from the hole's edge by fitting a square of cloth rim tape over the valve stem and to the inside of the rim. I poke a small hole in the tape to give a tight fit against the threaded stem. This has been reliable for me on many steel 27" rims, and I do not use a nut.
I use both Presta and Shraeder valve stems with old 27" rims drilled for Shraeder. When I use a presta valve in a Shraeder hole it is only to be able to use lighter-weight Presta tubes. My carry-along spare tube has to be Presta though so that my Presta-only mini-pump can reinflate the tire on the road following a tube swap-out.