Has anyone ever heard of this? I'm not sure how it happened, but when i went to replace my tire today, I found that I had two stem lock nuts on my valve. One inside the rim and one in the normal place. Not sure if the shop did this for me a awhile back or if I did this absentmindedly last time i changed it... Anyway, it didn't cause any problems and I put at least a few hundred miles on it like that.

Any reason to do that? Thanks!

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    Does your rim have a 6mm Presta sized hole, or a 8mm Schrader sized hole? Could be the first nut on was in lieu of a grommit ? – Criggie Apr 30 '16 at 21:44
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    Yeah, the usual reason for that is a hole that's too big for a presta tube and using the nut to take up some space. – Batman Apr 30 '16 at 23:27
  • nope. Rim has the proper presta hole... – ss ulrey May 1 '16 at 0:34
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    Then assume whoever installed it was drunk. – Batman May 1 '16 at 1:21
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    Assuming the rim is drilled for Presta, there is no reason to do this, and doing it could potentially lead to premature tube failure. – Daniel R Hicks May 9 '16 at 18:02

It is a commonly used quick and dirty fix when you don't have a purpose-built grommet to install in a rim cut for a Schrader valve. It may also not be a terrible idea if, for whatever reason, your Presta-hole rim has a burr or sharp edge and you want to avoid any possibility of problems with that.

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No, there is no reason for that type of installation unless the whole in the rim is sized for a Schrader valve, rather than a presta valve.

It is, as you found, unlikely to cause an issue though.

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