It definitely takes time. I started riding this past summer and was going 10-12 mph. After a winter of riding on a trainer I've been outdoors and when I'm not waiting at traffic crossings my speed was at 17-19 this Saturday on my hybrid. I have an r600 from 1995 and I've only taken it out twice since I got it and was maybe 2-3 mph over what I do on my giant hybrid. Silly question, but are you tracking your cadence and specific gears on each bike? Maybe something there is accounting for the similar speeds?