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808s are 81mm deep. So you want valve stem + extender to be at least 100mm to get sufficient engagement with the pump.
Do they make a tube with a 100mm stem so that you wouldn’t have to use the extender?
80mm is the longest I have seen.
Not that I know of. I saw 80mm at trisports, but 60 is normally the longest I’ve seen.
If you were to find something like that, there is a good chance it would rattle against the sides of the 808. I ran into that with my tubulars. I run tubular EVO II CXs which have a removable stem. I put a 100mm stem on the tubular and mounted it on my 808 and found that it rattled, so now I just use the zipp extender that came with the 808.
80 is the longest i have seen, but whatever you do get the ones with
the removeable valve stem and screw the extender on whats left of the valve stem on the tube and then screw the tip that you removed onto the valve extender
that way most of the moving parts are on the outside of the rim
waaayyyy easier to deal with
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I don’t think that they are advertised anywhere yet, but we have our own tubes and extenders now that are ALL aluminum…and move the valve core outside the rim. that I know of, this makes for the lightest long valve setups anywhere, also both tube and extension have wrench flats for easy assembly and rubber o-ring seals. I’ve been using them for a while across numerous wheelsets and it has proven to be a really easy and solid solution. We’ve also made it easy by branding the lengths of extension 303, 404, 808, etc… Other than that, you generally need a 100mm of valve for an 808s.
http://www.zipp.com/accessories/tires.php
Josh
Why not just make the tubes with the required valve stem size and avoid all of the hassle?
volume, standardization, revenue, etc.