This triathlon bike‘s frame is cross geometry double triangle with a sloping top tube. Specific alloy used in the frame or the butting could not be found other than Trek’s cryptic specification calling it ‘Alpha Gold Aluminium’. Fit and finish is absolutely good. Trek uses this same frame throughout their entire range of dual sport ‘8 series’ bike. The frame geometry is quite comfortable. Infact this is one very nice aspect of this bike that left a lasting impression despite few other drawbacks.