Tubes and Valve Extenders

It's a good idea to carry a spare tube either with an extended presta valve (some manufacturers make up to 100mm length presta valves) or to have a tube pre-configured with a valve extended using teflon tape on the threads to insure an airtight seal.

Chrissie Wellington was leading Kona one year, flatted, got her spare tube out and... oops. Almost cost her the race.

Several things you need to consider.

1.  Are the valve extenders you're using compatible with all of your tubes?  If you're using latex tubes with removeable cores, those will likely use different valve extenders than your standard butyl tube that you may be carrying as a spare.

2.  If you are running different wheel depths, then the easiest thing to do is prep your spare (and test it) to the longest common denominator. 

3.  If you need different length valves because your running a disc, then what I do is prep a spare tube that has a valve that will work with the disc, and add an extender that will work with the front (again...test it).  If my disc flats, just remove the valve extender.  If the front flats, you're already good to go.  You want to avoid having to add the extender when changing a flat since you won't be 100% sure if the seal is good.