On Mon, 16 Jan 2017 21:51:38 -0800, Jeff Liebermann
wrote:

On Mon, 16 Jan 2017 23:05:43 -0000 (UTC), Duane
wrote:

The idea of two pounds worth of tubes to avoid putting air in my tires
doesn't parse at all.

Let's do it by the numbers.

The tubes I usually buy are these:
http://www.nashbar.com/webapp/wcs/stores/servlet/Product_10053_10052_175629_-1___205038
26x1.5" for $4.79ea. They weigh 176g (0.39 lbs) and they leak air.

The proposed leak proof tubes:
https://www.amazon.com/Sunlite-Thorn-Resistant-Presta-Valve/dp/B0063R2GJW/
26x1.5" for $15.36ea. These weigh 572g (1.26 lbs).

For two tires, that a difference of:
2 * (1.26 - 0.39) = 1.74 lbs (789g)
Not quite 2 lbs but close enough.

The average 26x1.5" tire

seems to weigh about 550g (1.2 lbs). Ignoring the weight of the
wheel, with these tubes the rotating weight will increase by:
1.74 / (2 * (1.2 + 0.39)) = 55%

Offhand, it seems a bit too heavy to be worthwhile.

Please note that my original problem was not to find the best thorn
proof tire, but rather one that doesn't leak out of the box. I don't
seem to experience any sudden releases of air, but instead get slow
leaks. On the wheels in question, I ride on pavement.

Inner tubes come in a myriad types and prices. If you buy the absolute
lightest, thinnest, tubes, they will leak, but if you buy thicker
inner tubes they will usually be cheaper and may leak a bit but not to
the "pump them up every day" extent.

It used to be that "sew ups", or "tubular's", were the last word in
bicycle tires and, as I remember it, they did require pumping up
practically every time you got on the bike. (and I don't remember
anyone complaining about it :-)
--
cheers,

John B.