Originally Posted by
Chombi
I'm surprised again to see yet another TT frame built with heavier tubing (Cromor). You would think that they would use at least Colombus SL for these bikes, but there must be a concious design decision to use the heavier tubing to meet the particular needs in time trials?? Are they looking at these bikes more like track bikes where frame stiffness is a big goal?
Chombi
Cromor tubeset is approx 1/2 lbd heavier than SL. The frame stiffness requirements for a largely constant and relativley low torque effort of time trial are less than for a typical road bike. Note that in the old Columbus catalog, they list that thier lightest KL road tubing (.7/.5mm) as suitable for time trials.
http://os2.dhs.org/~john/catalogs/Columbus-tubes.pdf
The road bike needs to be able to sprint and climb well, so needs to be stiffer to withstand the higher peak torque. About the only time a TT bike sees much torque is at the start and turnout, and even those are gradual accelerations in comparison to a finishing sprint. A lighter (limper) frame on a TT bike wouldnt be much of a problem in terms of stiffness but the lighter weight also wouldnt really be any faster on a flat course. If there are uphills involved, a TT position bike is the wrong bike for the job anyway!
I would think that the selection of cromor was probably largely just an economic pricepoint decision, particularly since the performance of a TT bike would not be effected much by either a lighter frame or a stiffer frame. Spend the $$ on some aero wheels if you want to go fast.
+1 for American Classic hub ID.