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Water bubbling out my wheels

Jim Will Fixie ItJim Will Fixie It Posts: 72
edited September 2011 in Workshop
Right, think this is the right place for this question, so here goes. After a long, steep descent from Priddy to Draycott in Somerset, I think I could smell my brake pads burning - so, I knew my rims had got pretty hot!

5-6 miles later, I was halfway through an ascent of Cheddar Gorge when I heard a loud hissing sound. 'Here we go, a visit from the p******e fairy,' I thought. I leaped off and checked the front tyre but it was still fully inflated.

The hissing was still continuing so I checked the valve, thinking maybe, somehow, it had unscrewed itself. Nope but, to my surprise, water was bubbling out of the valve hole in the rim! It actually looked like it was steaming in places.

It kept going for a good minute or so, creating a small pool of water on the road. The water felt cold but, there was so little of it in relative terms, that it probably cooled on contact with the tarmac.

Very strange, but then I thought I had the answer. My bike has recently been kept in my (not so waterproof) shed. So, I reasoned, that some water had somehow got between the tube and the rim and then boiled on the descent from Priddy. As the pressure rose it eventually forced its way out.

This seemed to be logical conclusion until I thought that my rims (and thus the water) should have cooled by the time I had cycled the 5-6 miles from Draycott to halfway up Cheddar Gorge.

What are everyone's thoughts, as I've never seen anything like this before?


  • Simon GSimon G Posts: 41
    I can't really explain how the situation which you describe might have occurred, but I do know that water can act in rather strange way if it suddenly comes into contact with a very hot metal surface (there are loads of examples of this on youtube).

    When cold water hits a very hot surface, it won't boil, but just kind of sits there and rolls around. As the hot surface cools, the situation changes and the water will eventually spit/steam and boil away. Weird!

    Simon G
  • keef66keef66 Posts: 13,123
    I doubt you've boiled it, but the hot rims will have caused the air twixt tyre and tube to expand dramatically forcing the water out of the valve hole.
  • As above really, the heat from the rims could cause tyre pressure to increase. Its probably this pressure increase that has forced water that has found its way into the tyre back out.

    Good effort to get the brake pads burning anyway - proud of ya!! :lol::lol:
  • Thanks guys. Could the above situation occur 5-6 miles later though, as I would've thought my alloy clincher rims (2006 Kysrium SSC SL) would have cooled down by then, no? Though I suppose that doesn't stop the tube pressures from increasing and (eventually) pushing the water out the valve hole.

    I'm also assuming the water got in thanks to the combination of leaky shed, non-waterproof cover and English summertime! If that isn't where the water initially came from I'm stumped...

    Oh, and Paul, cheers. I thought it was pretty impressive. I pulled up at a junction and thought 'What's that?' Then, from years of experience smelling burning clutches, tyres and brake pads at race tracks I realised what I'd done (and I saw a thick black line around my rims!

    The hill was so ridiculously bumpy it was either to ride the brakes for two miles or end up supermanning into the hedge!
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