Steel frame sizing - bikes with extended seat and head tubes

[RobWJL]

The image shows a late nineties x-light. It's a little different to the current version as it has seat and head tubes that protrude above the top tube by around 2cm.

My question is, does this change the method of sizing to one's size/measurements.

In terms of seat tube size, I usually suit a 61 ctc.

This bike is 62 centre to top which would suit me - but only 59 ctc.

Do these extended tubes compensate for the lesser standover height at all?

Confused!

Ps I know seat tube size is not the full story when it comes to sizing..

 

[t47b]

Re:

Ctc will give you the accurate stand over height i.e. position of the top tube plus half the diameter of the frame tube and if standover is critical the new one is 2cms lower.

The top of the St will only determine the amount of seat tube exposed i.e. 2cms less on show.

 

[Chapeau! Velo]

Re:

The larger frames often have a slight extension on seat and head tubes for strength. Top tube CTC is the critical measurement / indication of the size for a stock frame.

 

[The History Man]

See my Roberts for explanation in thread re criterium.

 

[Leatherseat]

Larger Colnago's (I think 61+) use 'Freuler' sizing. I believe Herr Freuler was a tall Swiss Pro from a few years back.

The Freuler system is just a continuation of the longer top tube, longer seat tube, taller head tube pattern over the sizing range. The difference is that the top tube is not raised. This gives a slightly stiffer main triangle (because smaller triangle is stiffer). The key is not to worry about ctc seat tube; just check the top tube and head tube to ensure you fit and get sufficient handle bar drop etc.

Colnago used this approach across all materials, not just steel. Dario Pegoretti uses a similar approach.

Hope that helps,

David