I have the Giant 2003 touring bike and would like to know what the best way to lower the gearing would be. I have been out riding without lots of gear and on steep climbs it gets pretty tough. Would it be better to change the some front rings, back rings, cranks ect? Also would any of this effect the shifting? Would I have to replace derailleurs possibly? The drivetrain is Shimano 105. Any comments would be great.