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The Schrader valve retreats back into the inner tube because there is nothing to hold it in place against the wheel rim. Despite having an outer screw thread on the protruding valve nothing is there on that thread, apart from the valve cap. When the pump is applied it pushes the valve assembly into the tube making proper connection for pumping difficult and even damaging the inner tube as each stroke of the pump handle causes the valve/pump connection to move against the metal of the wheel rim.

Back in the day every Schrader valve had a retaining nut/thumbscrew to keep the valve stationary -- rock steady -- while pumping the tyres. If this omission is now standard it is a retrograde step and I want all of my valves to have a retainer nut/thumbscrew to avoid damage and make pumping much easier and more efficient. Are these available? How did this crazy change come about?

Yes, I am an oldtimer and my earliest cycling days were at school in the 1950s.

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    The restrictions on new users are mostly to corral everyone into the same way of writing a question - it's not intended to restrict you from asking. Great first question, keep it up!
    – Criggie
    Jun 19 at 6:18
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    All Schrader pump heads I’ve used required minimal force to attach to the valve. I don’t use the nut, even with Scalverand valves (which usually require some force) and haven’t had any problem so far.
    – Michael
    Jun 19 at 6:40
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    Once you have such a thumbscrew, you can just keep using it forever. No need to throw it away with the tube. Your local bike shop should have some cheap. Jun 19 at 6:45
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    @Michael it depends on your tyres - supple tyres make it easy to apply a thumb from the other side to get the chuck on initially, but tough sidewalls (e.g. Marathon plus) are less convenient - ok at home, but not handy with a fiddly roadside pump.
    – Chris H
    Jun 19 at 10:16
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    I kind of doubt that the nut actually provides stress relief for the tube. It just holds the valve in place and actually makes it impossible for it to bend.
    – Michael
    Jun 19 at 10:59

3 Answers 3

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Schwalbe tubes still have this feature. Schwalbe tubes are also high quality tubes with moderate weight, consistent construction (no lumpiness near the valve) and high latex content (helps rolling resistance and improves sealing ability with latex-based sealants like Stan's). If you want threaded Schrader valves I suggest stop buying the cheapest tubes and buy schwalbe tubes for a couple dollars more.

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    Impac are schwalbe’s cheaper brand and use the same valve. Continental usually have this feature too
    – Noise
    Jun 19 at 15:58
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Because it makes the tubes less expensive (no need to include the nut, and they can use less metal in the valve construction because they don’t need the screw thread to go all the way down), and most Schrader pump heads don’t need enough pressure on them for this to be a significant issue.

In other words, it’s a way the manufacturers can save a few cents on each tube (which actually translates to a lot of money) without significantly impacting usability for a majority of users.

However, if you really want to use tubes with retaining nuts, you can still get them, they just only tend to be found among premium tubes. Schwalbe still makes their tubes this way, and I’ve seen a few other instances of other manufacturers doing this for high-end Schrader tubes.

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Racers shave grams where possible, so those chasing incremental-gains would remove valve stem nuts and caps, and would choose valves barely long enough to get access to.

This was all in the name of weight saving and slightly aero benefits from not having threaded shaft in the airflow.

Separately, deeper section wheel rims with aero shapes often lack a flat-spot on the rim where the nut can recess into, so they create an aero discontinuity because of the flanges poking out.

Manufacturers will happily tout "loss" of a feature for performance reasons, where for them it is simply a manufacturing simplification. Some presta valves specifically come without threads so they are smoother. This precludes the use of a locknut completely, perfect for the high-speed racer where 3 grams might make the difference between win and loss.

For the bulk of riders, a locknut will not make a difference in performance, and is a quality-of-life feature that can help with pumping. You're totally fine to seek the products that suit your riding and preferences, and as @bettersense says, Schwalbe make nutted valve stems for Schrader valves (aka AV valves, car valves etc)

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    Do racers use Schrader valves?
    – ojs
    Jun 19 at 6:27

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