Originally Posted by
AlmostTrick
I assumed the "3rd butt" is near the center of the length of the tube... as in the tube actually has three different wall thicknesses, but maybe you know something I don't?
Maybe I do, but let's not go there.
A single butted tube, such as is used for the seat tube has one reinforced (buttressed) end.
a double butted tube, used for the top and down tubes, is thicker at both ends (and thinner in the middle).
I
believe* that a
triple butted tube is analogous to a triple butted spoke, where the two ends are of different thickness. So you have 3 gauges, the thicker end, the not as thick end, and the middle which is thinnest.
But no matter what marketing calls it, you can only buttress 2 ends of a tube. (except in 4 dimensional space, where tubes might have 3 ends)
* I said
believe, because while I've described one use of the term I'm familiar with, I have no way of knowing what marketing is up to these days.