Transitioning from running to biking due to lower back issues I am 50yrs old and 5’7” 155 lbs. athletic and in good shape (just a bad back). Until recently I ran 25-30 miles weekly and still hit the gym hard 4-5 times a week. I am looking at the Giant Defy advanced 3, Trek Domane, and Cannondale Synopsis. Have not ridden any of the bikes but plan to in the next few days to ride ea. Obviously comfort will be the most important part for me. Value wise the Giant has a Carbon frame and disk brakes. I am a beginner rider and will primarily use bike for exercise, group rides and maybe some bike challenges but not hard core racing. I don’t do anything easily so I will ride the bike hard I plan to ride at least 20+ miles a few times a week and 40+ on the weekends.Any advice, appreciate any comments?