Inner tube sizing - daft question

rodgers73

I've got 700c wheels with 25mm tyres fitted on my bike. I'm buying new tubes online but I'm suddenly struck with fear over what size to buy!

I'm guessing as long as it says 700c it will fit, but is that enough? There's always a second rating on there (18-23, up to 25, up to 28 etc). I know this is a stupid question but is there a danger I can get a tube too big or small despite the circumference being correct??

Also, what with the different sizes and lengths of valve stem? I have a standard track pump - does it matter whether I get a 52mm or 60mm presta valve??

wishitwasallflat

The second set of numbers is the tyre width; so for a 25mm tyre you are looking for a range that has 25mm in the range it fits e.g. 700 x ?? to ?? make sure the number 25 lies between (or is included in) the numbers ?? and ??

like:

http://www.evanscycles.com/products/con ... e-ec017412

or

http://www.evanscycles.com/products/sch ... 8-ec001872

The valve needs to be long enough to extend through the rim far enough out so that you can fit a pump head onto it - generally if you have ordinary profile rims then the standard length will be fine it's the deeper - aero type - rims that tend to need longer valves. That said though I just got Shimano RS10s which are pretty ordinary and not overly aero (AFAIK) but the next tubes I buy I will probably get longer valve stem ones as the standard ones I have are just long enough and no more.

If in doubt measure the valves on the ones that are in there already also the tubes in there should have a size printed on them

Ouija

Don't worry about it. The recommended thickness is just an indicator of how much the innertube will stretch when inflated (the thickness of the rubber lining will get thinner and thinner the more you inflate it). Put a tube that says "upto 25mm" in a 28mm tyre and it will stretch a little thinner when inflated so that the possibility of penetration/puncture is slightly increased. Likewise, put a innertube that says "upto 28mm" on a 25mm tyre and it's not going to stretch as much when fully inflated, so the lining of the innertube will be thicker and less prone to puncture/penetration. Some people like to do this specifically to make the innertube more durable. Others like to put a innertube designed for smaller sizes into larger sized tyres just to save weight (at the risk of the tube being stretched a little thinner, as mentioned).

rodgers73

OK, thanks - I get it now. And the valve sizes??

wishitwasallflat

wishitwasallflat wrote:

The valve needs to be long enough to extend through the rim far enough out so that you can fit a pump head onto it - generally if you have ordinary profile rims then the standard length will be fine it's the deeper - aero type - rims that tend to need longer valves. If in doubt measure the valves on the ones that are in there already also the tubes in there should have a size printed on them

If this isn't clear please follow up and I will try to explain

rodgers73

No, that's clear - I missed that post somehow!

Thanks all