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I have a Continental Road inner tube with a threaded presta valve. I also have a threaded bike pump which I screw onto the valve to inflate the tube.

When I try to unscrew the pump, the uppermost part of the valve unscrews and detaches from the main body of the valve and all the air rushes out.

Presta valve with labels for both parts

Is it normal for a presta valve to be separable into two parts like this? How can I prevent this from happening?

David Tuite
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3 Answers3

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The correct answer is yes and no. There are in fact two types of Presta valves: One where the core can be removed. Those are often used with tubular tyres so that the inner tube can be filled with a sealant (latex) fluid. Some higher quality tubes also have removable core valves for the same purpose. Normal and cheaper tubes have Presta valves where the core cannot be removed.

There is a special tool to be used for handling the core although like @Michael said the (careful) use of pliers also works.

Another reason for a removable core is the possibility to use valve extensions with high rims.

Carel
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    You'll also see these on tubeless mountain bike setups so you can remove the core and add sealant as well. The picture in the question is actually the valve from a tubeless mountain bike setup. – Benzo Oct 15 '15 at 15:41
  • @Benzo, that setup is not specific to MTBs, my road bike runs valves pretty similar to the OP pic. – Klaster_1 Нет войне Oct 16 '15 at 05:17
  • Agreed that the presta valve is used for road bikes too. However the one in the picture is for a tubeless system used on mtb and cx bikes, as indicated by the tapered base below the valve (instead of being permenantly attached to the tube) which seals tightly against the opening in the rim when the lock nut on the outside of the rim is tightened. – Benzo Oct 17 '15 at 13:16
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    @Benzo tubeless systems aren't unique to mountain bikes anymore – Paul H Dec 15 '20 at 15:47
  • @PaulH: Benzo's answer dates back to 2015 when tubeless was quite exotic on roadbikes. – Carel Dec 16 '20 at 15:41
  • @Carel Disagree somewhat that they were that exotic in 2015. I'm hardly on the leading edge of anything and I had a tubeless road setup in 2011. Also, this question was on the front page in 2020, so adding more current info seemed appropriate – Paul H Dec 16 '20 at 15:55
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    I agree. Tubeless is everywhere now. Not just MTB. – Benzo Dec 16 '20 at 17:54
  • umm no, tubeless is not everywhere. – john Sep 05 '23 at 23:59
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Yes it is normal. You can carefully tighten the valve core with pliers or special tools. Medium strength Loctite helps a lot too.

Michael
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It happens to me every time I buy new tubes. You just tighten the valve and it won't happen again.

dlu
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JMAR
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  • Welcome to [bicycles.se] @JMAR. When yo have enough rep such a short post should be made as a comment. I encourage you to check out the [help] to see how this site works. Again, welcome. – andy256 Oct 15 '15 at 22:47