Snapped Presta

[mark a.]

I was just doing the final prep before heading out on a ride, pumped up the tyres and snapped the little nut and some of the stem off the presta valve on the rear tyre. It now looks like a narrow Schrader.

The valve still worked (both letting air in and not letting air out), and I couldn't be bothered with the faff of changing a tube when I was already late, so I went on my ride with the valve like that. I didn't have any problems with the tyre.

Is there any rush for me to change the tube, or can I just wait until my next puncture / service / slow deflation? Will the valve suddenly let go, somehow, while in this state?

[andrewjoseph]

the valves work by the air pressure inside the tube closing the valve once it's greater than outside pressure, so it's self closing.

my concern would be that if it is now not seating properly then it may leak, if the tyre goes very soft and you try to pump it up you may blow the valve remains inside the tube.

one thing to check is if the valve core is removable. if the valve has flats on it you may be able to unscrew it and replace.

[mark a.]

Ah, so the nut prevents the valve from disappearing into the tube? I can see how that could be a problem the next time I need to add a load of air.

I'll also check to see if it's a removable core. Good idea, thanks.

[gregoryoftours]

I don't know if it does stop parts of the valve dropping inside, but I guess if the seal isn't the best then tightening the nut pulls the seal tighter. It's also useful to tap on the undone nut with your finger to 'break' the seal to put air in.

[drossall]

The nut locks the valve closed. Often it will self seal, but the nut helps. I remember, decades ago, a friend's tyre going down every mile or two. We couldn't work out why. Turned out he was having a brain-storm and not tightening the nut.