semi-dumb valve stem question

I have three spare tubes in the saddlebags right now. If I recall
properly no two have valve stems of the same length. The rear tube on teh
bike right now, the stem is something like 5cm (2") long, while the one of
the front is more like half that.

Why? Why aren't all valve stems more or less the same length? Why would
one need a valve stem 5cm long?

On Apr 4, 10:55*am, Doug Smith W9WI wrote:
I have three spare tubes in the saddlebags right now. *If I recall
properly no two have valve stems of the same length. *The rear tube on teh
bike right now, the stem is something like 5cm (2") long, while the one of
the front is more like half that. *

Why? *Why aren't all valve stems more or less the same length? *Why would
one need a valve stem 5cm long?

Depends on rim depth. Single wall rims require the shortest valve of
course, while something like a Velocity Deep V requires an extra-long
valve. I carry a presta long 700x23 tube in my utility bike's
saddlebag, even though it uses wider schrader tubes. I figure it'll
work in a pinch, and if I need to help out a stranger, I can pretty
much stuff it into most tire/rim combos for a limp home.

On Apr 4, 5:55*pm, Doug Smith W9WI wrote:
I have three spare tubes in the saddlebags right now. *If I recall
properly no two have valve stems of the same length. *The rear tube on teh
bike right now, the stem is something like 5cm (2") long, while the one of
the front is more like half that. *

Why? *Why aren't all valve stems more or less the same length? *Why would
one need a valve stem 5cm long?

Deep rims need long valves:

http://www.onetri.com/images/Product...o20Frontlg.jpg

As available rims have grown in depth, so to have available valve
stems, with what is considered long growing all the time.

Joseph

On Fri, 04 Apr 2008 10:55:17 -0500, Doug Smith W9WI
may have said:

I have three spare tubes in the saddlebags right now. If I recall
properly no two have valve stems of the same length. The rear tube on teh
bike right now, the stem is something like 5cm (2") long, while the one of
the front is more like half that.

Why? Why aren't all valve stems more or less the same length? Why would
one need a valve stem 5cm long?

One reason would be owning a Spinergy wheel, on which the 5cm stems
will just barely protrude through far enough for a Silca chuck to grab
them. Different aero wheels have different cross-sectional depths;
where a non-aero rim will typically need no more than a 25mm stem at
most, severe aero designs can require much, much more.




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