If you are at 140 mm and you want yo change it to 120-100mm probably you'll be able to do it, if you have good skills and the trail is easy. Nevertheless if you want more travel (100 to 140mm) surely you'll have to stop. It's because the adjustement head works better in one direction than in other (going down is easier than going up). If you have more doubts please ask! PD:Sorry for my bad english!