Hi, David,
Seat height should be measured from center of BB to top of the saddle ALONG THE SEAT TUBE LINE (which I realize seems to be an oxymoron). Definitely make sure you get that measurement sorted out. Google for "bike saddle height" when in doubt.
For 178mm guy to have a 77cm+ saddle height it does sound to be on the taller side. FYI -- so far people on size M generally fall under 172cm to 183cm (5'7" to 6' for the Yanks). So, without seeing your further stats and side on-bike photo, M seems to be the safer bet, especially since you need a decent amount of drop.
Cheers,
http://www.falcobike.com
https://www.facebook.com/falcobikeglobal
http://www.twitter.com/Falco_Bike
falcobike@gmail.com
Seat height should be measured from center of BB to top of the saddle ALONG THE SEAT TUBE LINE (which I realize seems to be an oxymoron). Definitely make sure you get that measurement sorted out. Google for "bike saddle height" when in doubt.
For 178mm guy to have a 77cm+ saddle height it does sound to be on the taller side. FYI -- so far people on size M generally fall under 172cm to 183cm (5'7" to 6' for the Yanks). So, without seeing your further stats and side on-bike photo, M seems to be the safer bet, especially since you need a decent amount of drop.
Cheers,
http://www.falcobike.com
https://www.facebook.com/falcobikeglobal
http://www.twitter.com/Falco_Bike
falcobike@gmail.com