Saturday, April 9, 2011

VeloNews vs Tour, Cervelo vs Felt

Both the VeloNews aero bike test and the Tour aero bike test (my discussion of that test is here) examined the Cervelo S and the Tour AR. In the case of VeloNews, the bikes were tested "stock" with the exception both used Zipp wheels. Cables were installed and there was no rider. Tour on the other hand used a dummy rider (the only way to get a reasonably consistent position) and Mavic wheels. The Tour article is in German, so the finer details are beyond my comprehension. But they didn't use bar tape, while VeloNews used whatever bar tape the bikes had installed. Same deal with the saddle: the VeloNews bike tested bikes with "stock" saddles, while in the Tour test, the saddle was less important due to the use of a "rider".

Despite differences you might think conclusions about which bike was faster would be fairly consistent. But comparing the only two bikes tested by both magazines, this is not the case:

comparison of results

I averaged the positive and negative yaw results from the VeloNews test, since Tour reported values for only one side of the bike.

If you read Tour, and you think low yaw angles are the most important, you rush out and buy a Felt. On the other hand if you read VeloNews you definitely get the Cervelo.

Neither test result was without surprises. The Cervelo at zero yaw was slower even than the Cannondale control bike in that test. Nobody's ever looked at a Cannondale System 6 and walked away with the impression of aerodynamic elegance. In contrast, the Cervelo has a beautifully tapered head tube.

True, the Tour test overlooked the advantage of internally routed cables. But I can't help wonder how consistently the dummy was fit on the bike in each case in the Tour test.

So this sort of bike-to-bike comparison testing is very challenging. Far different than looking at weight difference, where you pop that sucker up on the scale and photo the result. Sure, there's subtleties, like what sizes to compare, and whether to compare naked frames or "modules", but wind tunnel testing is just in a different league.

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