[Yak] 20" tube in 406 rim?

[bikefridaywalter]

Rick,

Here's the straight scoop:  406 tires and tubes are totally ubiquitous.  BMX bikes, kids bikes, recumbents, folders, man there are so many applications for them it's ridiculous.  Furthermore, you can go to ANY department store that carries bikes and pick up a tire and tube.  Definately not the case with 451s, 349s, or 305s (yes, the OTHER 16"!)

But here's the caveat:  the 20" thing leads to a LOT of confusion.  If you have a thin tire on a 451 and a big tire on a 406 and measure the total diameter, they both seem to be about 20".. but they're not.  Which is why your original tubes are marked 18".. to further add to the confusion!  But believe me, it's still a "twenty-inch" tube.  At least if you mean the 406mm 20".  Ok, see the confusion?

Now bike shops (yes, this is a generalization and not true for all of them) have a tendency to assume that all the small wheeled folks are total losers and they don't bother trying to find the real answers to their needs.  The bike shop that cared would have thought, "I've never heard of an 18" before" and tried to figure it out.  Yours probably thought, "this guy is so stupid he doesn't even know he has a 16"!  Man, those recumbent guys are dorks!"  

So here's four ways you can figure out if you're getting the right thing:

1.  If you go to a department store, you're likely to find a wide 406mm tube.  If you find a 451 tube or a 349 (one of the, yes, believe it or not, TWO 16" wheel sizes!), it's because you're not in a department store.  If you have thin tires, you might be a bit out of luck if they don't have any thin ones, but at least they have 406mm.

2.  As aforementioned, if the width is expressed as a decimal, it is generally a 406 (i.e. 20x1.5-2) but if it is a fraction, it's generally a 451 (i.e. 20x1-1/8).  The 18x1-3/8 obviously destroys this whole trend, but it's obviously really weird anyways.

3.  Remember, you have a standard BMX wheelsize.  451's are often used for racing BMX, but this is far less common than the 406.  You might walk into the bike shop and say you have a <fill in the blank here> wide BMX tire you need a tube for, i.e. "I need a tube for a BMX with a 1.5" tire on it."

4.  Get a tape measure!  Pull out the tube, lay it out so it looks round and measure the inside.  There really is a big difference between 406mm and 451mm.  You won't likely be capable of measuring those numbers exactly, but you'll be damn close.

Hope that helps.

Walter


---
ride free!
http://tinyurl.com/5xqj8


Mourn the victims. Comfort the survivors. Stand for peace.
Light a virtual candle for London: http://www.care2.com/go/z/london

http://www.Care2.com  Free e-mail. 100MB storage.  Helps charities.