Originally Posted by red house
-thanks for the info...btw, what is 8/5/8 and 9/6/9? do you know who makes the tubeset? -reynolds, columbus, TT -etc?
First off, my answers are educated guesses. I'm not sure about the exact nature of Tony's frames, but I have a pretty good idea. Tony would be the authority, of course.
9/6/9 and 8/5/8 refers to the wall thickness of double butted tube in the main triangle: the top tube (T/T), down tube (D/T), and seat tube (S/T).
A double butted tube has five sections from end to end:
butted - tapered - thin - tapered - butted
On a 9/6/9 tube, the butted ends are 9/10s of a mm thick and the thin center section is 6/10s of a mm thick. And the tapered sections go from 9 to 6, or vice versa.
8/5/8 tubes are 1mm thinner in the butted and thin sections.
The IRO web site states that the Mark V Pro uses heat treated tubes. I suspect that Tony spec'd the heat treated main tubes as 8/5/8. Heat treating raises the strength of a tube. So thinner walls can be used. This results in a lighter frame.
I could go on and talk in more detail about the tubing, but I'd like to get Tony's nod before doing so.
Let me just say that the Mark V Pro is a VERY nice frame, as are all IRO products.
shows a typical Kogswell frame and the tube dimensions that are used.
I'd be glad to talk about those tubes too.
An interesting one is the D/T. We call a 'bulge butted' D/T. The diameter and wall thickness get larger at the top. This allows for the use of a standard 27.2mm seat post while maintaining enough material (1.2mm) to support the use of a seat clamp.