Anyone have a similar dilemma? I have had lower back issues the past few autumns when transitioning to my road bike on the indoor trainer. When I drop the saddle .25," the power and fluidity returns to my pedal stroke and my back feels great--and I am able to go very hard. One major variable is that I run 175mm on my MTB and 170 on my road bike. I work long hours on a computer, and try to frequent breaks for posture and breathing. Stretch regularly as well.