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I have a 20" Sun Rims CR-18 rear rim. This rim has a cylindrical metal sleeve that goes through the valve hole. Not sure where that came from, as I inherited the rim with the bike when I bought it used.

When I was changing the tires after riding this bike through the New England winter, I noticed that the valve on my tube was stuck to this sleeve in the rim. I used locking pliers to attempt to wiggle the valve free, but instead, it sheared off the end of the valve and left the rest of the valve fused inside the rim.

sheared off valve

I had to drill the remainder of the valve out. When it eventually dislodged, it released some gray powder.

inside of rim with gray powder

What caused these two parts to fuse together like this, and how can I prevent it in the future?

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  • I'm guessing you're jamming a Schrader valve into a Presta hole.
    – Daniel R Hicks
    Apr 5, 2017 at 23:43
  • @DanielRHicks good guess, but no. It's a presta valve as you can see in the first photo, and inserting it involved no jamming. It was only fused when I left it in there over the winter and tried to remove it.
    – Mike Eng
    Apr 5, 2017 at 23:56
  • The "gray powder" may simply be aluminum dust, or else corrosion of some sort. But I see something projecting through the hole in the top picture. Is that possibly a bushing to adapt a Schrader rim to a Presta valve?
    – Daniel R Hicks
    Apr 6, 2017 at 0:11
  • @DanielRHicks yes, the valve seemed to have quite a bit of corrosion on it. Yes, there is a metal cylinder projecting through the hole. Not sure if it's an adapter. I updated the original question to clarify that.
    – Mike Eng
    Apr 6, 2017 at 0:31
  • Yeah, very likely that "sleeve" is an adapter. Likely it's gotten mangled a bit over the years. But the new Presta valve stem should fit easily through the hole -- if not it needs to be drilled out or the sleeve removed and a Schrader valve used. And you may want a light coating of grease on the surfaces before assembling. (Keep it away from rubber parts and the brake surfaces.)
    – Daniel R Hicks
    Apr 6, 2017 at 0:38

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Sounds like galvanic corrosion. If you're somewhere that salts their winter roads, this is why people ride beater bikes.

A fix might be to smear the valve stem and around the valve hole with a thin layer of RTV silicon or possibly a grease to stop the two surfaces coming in direct contact.

Combining brass and aluminium is generally considered incompatible

You might prefer to choose tubes that have rubber up the sides of the valve stem (not uncommon on Schrader but rare on presta) or some tubes use stainless steel valve stems.

To be honest, I'm surprised there aren't more corrosion problems between alloy rims and brass valves.

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    I've never seen rubber sides on a Presta. A Presta valve is the same diameter for its entire length, and there's no practical way to have a rubber sleeve on the "base" of the valve the way you see on Schrader valves.
    – Daniel R Hicks
    Apr 6, 2017 at 0:40

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