I inherited this bike with this funny looking stem. Is this broken? How do I inflate it?

enter image description here

  • Note what the other answer in the link mentions at the end. The top part must be unscrewed first. Commented Apr 26, 2020 at 7:00

1 Answer 1


This is what's known as a Presta valve. It doesn't look broken, it looks like it is all there and the valve is in the open position because the captive nut at the very tip of it has been unscrewed.

You can test if it is working by just nudging the end of it upwards briefly, some air should escape. This is good to do before inflating anyway to see that the valve has not become stuck before you pump.

You need a Presta compatible pump (some have a double head and some can be converted), or a small brass 'Presta valve adapter' to convert from a normal car valve (Schrader) type pump.

A 'track pump' is a bicycle specific pump that typically has a head that suits both type of valve and is available from all good bike shops.

Here is an image showing operation of my preferred style of pump head, that I found online on multiple sites with no attribution (but probably Topeak themselves):

Twin pump head operation schematic

  • Yes, that's a Topeak pump chuck.
    – Carel
    Commented Apr 26, 2020 at 19:15

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