# 18-23 tube in 25 mm tire?



## Sir Psychlo (May 29, 2004)

Hi,

Is there any problem in using an inner tube made for a slightly narrower tire,
for example a 700x18-23 mm tube in a 700x25 mm tire?

Thanks.


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## xxl (Mar 19, 2002)

Sir Psychlo said:


> Hi,
> 
> Is there any problem in using an inner tube made for a slightly narrower tire,
> for example a 700x18-23 mm tube in a 700x25 mm tire?
> ...


Not really. Some might argue that the "small" tube may be a bit more prone to flat, given the increased surface tension on the skin of the tube from the increased pressure, blah blah blah. Who knows, there may actually be that rare circumstance where a thorn or nail manages to break through the Kevlar belting but not puncture the tube; you would be at risk (theoretically). But, since you're so close to the proper size tube, you should be good.

Note, too, that tire sizes (unlike most tube sizes) are notorious for being capriciously measured widths. It's not uncommon for one maker's 700x23 to be wider than another's 700x25; I think Sheldon Brown talks about this...


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## bigbill (Feb 15, 2005)

Sir Psychlo said:


> Hi,
> 
> Is there any problem in using an inner tube made for a slightly narrower tire,
> for example a 700x18-23 mm tube in a 700x25 mm tire?
> ...


I use a 18-23 tube in the rear tire of my commuter bike with a 28mm Armadillo. It is a big 28mm. The front wheel has 28-38mm tube in the 28mm tire. The back tire has a small tube because I ripped a valve stem one night at about 10:30 and that was all I had. I run my tires at 90#. I put air in the front once a week to go from 80# back to 90. The back tire is 75# each day by the time I get home. I think it might be caused by the small tube stretched thin and leaking more air. Back tires lose air faster, but not like this. I don't think this would come into effect for a 25mm though.


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## AJS (Aug 7, 2003)

bigbill's got it right. I use Specialized Turbo Road LVS 18-25 tubes in 25c tires all the time with no problem at 120+ psi. Also use them in 28c CX tires occasionally, and the tubes stretch out enough to get them up to 100 psi without seeming to be more flat-prone. 

If I go to a fatter tire than 28c, then I'll use a 25-32c or similar tube.

Only time I had an issue was with one of the 18-25 tubes being patched in the 28's that I forgot about, and it stretched the patch loose. Threw that one out, installed a new tube, A-OK.


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## Dave_Stohler (Jan 22, 2004)

It will work, until the day you try to patch the tube, and your fresh patch will snap right off when the tube expands to fill all that space. Some bike mechanics do this trick because it makes getting the tube inside the tire easier, but it's a very poor practice. Buy the right tube for the tire.


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## jtompilot (Mar 31, 2002)

The owner of the LBS recomended a smaller tube for my 23 tire. Ben using now for two years, no problems, no issues.


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## Sir Psychlo (May 29, 2004)

Thank you all for sharing your wisdom. The motivation for using
18/23 tubes in my 25mm tires is that some nicer (lighter) tubes 
only seem to come in the smaller sizes. If I go ahead with this 
experiment, I'll try to remember to report on my results later.


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