Yes I know, this is not a scientific study; however I found it interesting and would have appreciated reading this before I bought my bike.
I’ve been riding a Trek A1000 road bike converted to a tri bike. It was always a little too long in the cockpit leading to lower back pain after a couple hours. Of course, being a conversion I could never get low enough in front and it handled like a dog. I won’t even go into the wonderful experience of putting lots of miles into Sora components.
I recently got a new P2k. From the shop the bike fit was almost identical to my old bike, except I was no longer too stretched out. Every month I ride the same course on a 30’ time trial. 2 days after getting the cervelo, I rode it in the TT. 2 days later I rode the old bike. Weather and course were similar, the P2k TT had winds at 19mph, the Trek TT had winds at 12mph the course is roughly a square of 2 miles per side, flat with the wind coming from one of the corners. This was a rest week for me, so I was fairly rested for both TT. I was 0.9 mph faster on the stock P2k in basically the same position on both bikes.
After the TT I went through an exhaustive and detailed process to self-fit myself using all of Dan’s and John Cobbs writings.
All the following week I seemed to be going way too fast on the bike. The next weekend I had a 60 mile/6 mile brick. I was out of town and rode in constant hills. I don’t think there was ever more than .25 miles of flat. This was between Tyler TX and Athens TX for those of you who know the area. Keep in mind, I rode this as a workout. I set my PR for a 60 mile course, even though it was constant hills and 90 degees. My previous 60 mile pr was set on a totally flat course in cool weather.
All in all, from over a week of training (180 miles) it seems that the aero benefits of the P2k (bike alone) are worth 0.9 mph. The aero benefit of being in the best position and best bike fit that I am capable of is worth another 1.5 - 2 mph.
There are plenty of reasons that I would be faster on the new bike, pysc reasons, bar end shifters would add a little speed over STI, wheels are better, etc. During the week I took the P2k to the track and checked the computer because I didn’t believe I was really that fast. It was spot on.