Does the size (diameter) of a downtube affect frame stiffness or comfort in a meaningful way?
I have a custom steel bike with 853 OS tubing that has a 1.25" diameter downtube.
I am going to have another frame made and it was suggested that going to a 1.375" downtube would make the bike more responsive.
I am 140 lbs and 67 years old and ride mostly at moderate pace so I don't generate a lot of power but do like climbing out of the saddle.
In reading David Kirk's excellent article he suggests downtube size has little effect on drive train stiffness and it is the chainstays that matter most.
I am a little concerned that going too large on the tubing would take a away the feel of steel that I love.
Thanks for any feedback.