Some history on the C40 courtesy of: http://brown-snout.com/cycling/tech/_colnago-c40-family-tree.pdf C40 variants – introduced 1993-94. made famous by guys like museeuw, ballerini, tafi, bartoli, dekker, and bettini. • mk-1 – "the original" full carbon tube-and-lugs with the traditional rear triangle and constant-diameter downtube. these are generally found with a steel colnago precisa fork, but can be found with a similar looking alloy colnago fork as were used in the carbitubo. these will also have traditional down-tube shifter bosses. • mk-2 – continue with the traditional rear triangle, but introduced a tapered/flared downtube to stiffen up the BB. the chainstays were also beefed up – moved from a slim round profile to a taller oval profile, again to stiffen the BB. these also saw the introduction of the threaded shifter bosses integrated to the lower HT lug. at some point they moved to the Star carbon fork as an option, not sure if that was a late mk-1 or early mk-2 change – but came with the introduction of a threadless setup. note that you will often find C40s with a threadless steel precisa, as well! eventually went exclusively to the Star fork. note: colnago made several small running changes from year to year for these first 2 variants and i'm not sure that there was a really hard/fast cut from mk-1 to mk-2...it was almost constant evolution. • mk-3 – introduced the wishbone B-stay seatstay design. the chainstay/BB lug area was slightly reshaped, possibly to improve BB stiffness. also, at some point along the mk3-4 evolution they moved from an aluminum BB insert to a much more durable titanium insert. • mk-4 – introduced the diamond-cutout HP-stay chainstay design and name-change to "C-40HP". you may also find some that have a Force fork instead of the Star. • mk-5 – went to 1.125" front-end spec and larger tube diameters in the main triangle...also known as the C50!!! ;-)
