I was thinking about this thread as I was looking at veloviewer. Since I got my new bike, I've been worried that it's slower than my older bike which was exacerbated by the fact I commuted to work yesterday on my old bike and was quicker by 2mph. However, if I look at the rides from this year with the new bike compared to the old bike, I've done 2,500ft of climbing on the new bike and 500ft on the old one (for a similar distance). So it makes sense that the new bike has been slower due to the terrain!!