I have a Trek 820 mtb. The front derailler takes a lot of effort to shift from 2nd to 3rd gear. So much effort that it hurts my thumb. I believe that these are brifters. They are labeled Shimano Topswing S1S or 515. With this shifter you downshift with your trigger finger and upshift with your thumb.
I have cleaned and lubed the shifter and the cables. It seems like the return spring is very stiff.
I have another bike with the same shifter, but the cable on it comes up from underneath the BB and it wraps around the actuator. That bike shifts fine. On the Trek, the cable comes to the top of the actuator and it pulls up. I know this isn't a very clear description.
Is there something I can do to decrease the shift effort? Can I easily upgrade this shifter?
Thanks in advance.