My shifters require a lot of force to shift. Specifically, it's the thumb levers. Shifting from the small to large chainrings in front, and from the small to large cogs in back takes a lot of effort and it's making my thumbs sore. I remember taking my bike to the LBS and they cleaned and lubed the shifting mechanisms but I don't know exactly how they did it. It didn't seem to take them very long, either.
Anyone have a link or something explaining the procedure? Thanks.