In Reply To:
1) Why no P4?
2) If data was measured out to 30*, why is this data not reported?
That said... what wheels were used? I'd love to see a lot more information on this study before I declared it worthwhile at all.
I'm a bit surprised by these results - just because it's such a significant difference. With that said, I'm not really sure what they could've skewed here. Looking purely at P3 vs the 4000, as they fit similarly: aerobars, seats, wheels wouldn't seem to give one a significant advantage over the other.
Of course, they don't actually say whether they used the same wheels/bars/saddles/components on both bikes, or that the sizes were comparable, which could obviously skew the data (though it would be quite dishonest).
Also, according to cervelo's data, the P3 tests at ~700g of drag (0 yaw), the P4 at 575. cervelo also shows the P4 as worse at 10 yaw than 15, which kestrel doesn't. Kestrel has the P3 testing at 850g. Protocols can be skewed, but the final numbers can't, and the fact that cervelo could get 150g better than Kestrel definitely implies that the P3 was set up in some non-optimal way.