>>1147845For down tube: Shifting center of gravity forward and to the side. Manageable if you're slow or on flats but less than optimal at high speed or while ascending/descending.
Whether you're doing stem, down tube or bar end, you're moving your hands to shift thus forfeiting some level of control
Friction shifting is based on maintain tension along a line with the use of some mechanism. The friction utilized to maintain this tension is not as secure or static as the ratcheting systems you see in modern day shifters. Whether you notice or not, there is some level of "slip" that occurs with derailleurs utilizing friction shifters. To make it short: force is applied unevenly to a chain leading to greater wear, more stress, and greater probability of hardware failure.
Friction shifting will never be as accurate, precise and quick as modern day integrated shifters. This results of this is sub par performance regardless of environment, greater wear on the drivetrain, and greater potential for injury under high-torque scenarios (i.e. shifting while climbing).
If one must use friction shifters due to cost or to keep with tradition/fashion, go with top-mount thumb shifters. Otherwise, convert stem/bar-end/downtube to integrated (if your bicycle allows).
