After over 20 yrs of cycling on a mountain bike, 'up hill and down dale' I bought a road racer. I have spent every day for the last two weeks whilst off work for the Xmas breakcovering 30/40 miles, really enjoying the speed. Even cycling up usual hill climbs in the locality. Went back to the mountain bike for the last two days and today, doing my usual 25/30 mile circuits, but my upper leg muscles really ache after these rides. Consulted my LBS yesterday as to my riding position on both bikes, they confirmed I needed no adjustments. Why the aches? Does riding one bike differ from the other, using different muscles in different ways? I know the body position is different, does anyone else have similar aches in the legs, changing from road racer to mountain bike and vice versa?