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Thorn Resistant Tube

Old 10-02-12, 09:30 PM
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koolerb
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Thorn Resistant Tube

I just picked up a mismatched, but nice set of 700C rims at a garage sale for a project bike I'm just finishing up. So the front wheel has schrader valve not a presta, kinda weird. I went out and bought a Pyramid, Thorn Resistant 700X20-25 tube. Very heavy duty tube, like ridiculous heavy. I put a little air in before installing and noticed the tube diameter was a lot smaller for about a 4-5 inch area around the valve but didn't think anything of it, probably just reinforced in that area. But when I took the bike out for the maiden voyage I noticed a pronounced thump in the front wheel at anything over 15 or so mph. My first thought was the tube.

Have any of you had similar experiences with these heavy tubes?
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Old 10-02-12, 09:37 PM
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TR tubes are usually cheaply made and can have wall thickness varriations. This causes different expansions when partially inflated. Why did you choose this kind of tube? The thump could be from a poorly seated tire and not anything to do with the tube. Andy.
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Old 10-02-12, 09:52 PM
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IME, the stretch resistance of any tubes is way too low to factor in final size at riding pressures. The typical tube will expand and burst at 5-10psi, so at anything above that it's pressing against the tire whose dimensions are controlled by the fabric body plies.

If you're getting thumping, check for even seating, since that's the more likely problem.
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Old 10-02-12, 10:00 PM
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Thanks for the quick reply. To be honest I've never bought a 700C tube with a schrader valve; I thought all 700C tubes were presta. But when I was shopping for tubes at the LBS the first one I picked up was thorn resistant. The salesman said they were very popular. The bike is for my wife so I figured the additional safety wouldn't be a bad thing. The tire looks seated fine, and the wheel isn't perfectly true, but its pretty darn close. I think its got to be the tube. I'm just kind of shocked they can sell these these things.
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Old 10-02-12, 10:03 PM
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OK guys, I'll take a closer look at the tire. Thanks
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Old 10-03-12, 08:17 AM
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Two different valves on the same bike is going to be a pain. You can get thorn resistant tubes with presta valves and either grommets or aluminum reducers to make a Schrader rim hole fit a presta valve.
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Old 10-03-12, 04:56 PM
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HillRider - Thanks for the tip. I definitely need to do that.
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