Math check
100g of drag is about equal to 13.4 watts at 30mph?

100g=.98N 30mph=13.4 m/s

W=Nm/s

W=.98*13.4/1

or is my physics as rusty as I think it is?

Another quick question, about how many watts would it take to hold 30mph on a bike like this 450? 500? something in that range?

Tom,

Though I agree with you that the fixed offset looks conspicuous, bikes with similar shapes can test that way (and balance offsets can show the same thing...). But from experience I would imagine that offset is probably from a bar-set being 2cm higher up than on the P3C and a slight (maybe 10 grams) difference due to the rear wheel cutout.

My biggest curiosity is whether the bikes are set up to be ridden the same way (i.e. same rider position) or just how their geometries come.

I find the large jump in drag at -12.5 degrees curious. I wonder if that's a stall point or just bad data. If tested with a disc out back, I wouldn't expect that stall to hit until a bit later.

I do have Transition vs. P3C data. I've been reluctant to post as we only had time to test the bikes versus one another -- we didn't have a ton of competitors bikes, etc.

Mark

More than anything, I'd like to see all of the bikes pictured as tested. Does anyone know how the bikes were tested (i.e. w or w/o disc wheels, cables?, P4 tested with bottle, etc.)?

It's easy to see 50-150 gram differences in the tunnel due to stem variations, steerer lengths, etc.

And an additional repeat of one or more bikes would be great too.

Looks like the frame and fork are a huge improvement over the P3C, no doubt. I bet they gain 75-100 grams of drag just from improved tube shapes (especially the fork).

Mark

Tom,

Though I agree with you that the fixed offset looks conspicuous, bikes with similar shapes can test that way (and balance offsets can show the same thing...). But from experience I would imagine that offset is probably from a bar-set being 2cm higher up than on the P3C and a slight (maybe 10 grams) difference due to the rear wheel cutout.

My biggest curiosity is whether the bikes are set up to be ridden the same way (i.e. same rider position) or just how their geometries come.

I find the large jump in drag at -12.5 degrees curious. I wonder if that's a stall point or just bad data. If tested with a disc out back, I wouldn't expect that stall to hit until a bit later.

In Reply To

  exactly.....and what is the likelihood that they all used the same saddles, same stems, same aerobars, etc etc.....considering that could make all the difference in the world. then there's saddle height, and relative saddle heights that will be better/worse for each bike, etc etc. could a tall rider benefit more from one frame than a short rider etc etc? interesting stuff but i just don't see how you can ever get accurate results across the board that you can apply to the general audience.

Am I reading these graphs wrong, at 0 degrees is the Felt DA listed at 725 grams of drag in one chart and 700 grams of drag in the next?

Cervelo has done a marvelous marketing job here. Even producing a graph showing that all their bikes are the fastes.
While I don't know anytning about the test itself, I know it's easy to "prove" that one product is best - just remove better products from the test/list.
(Look, BP Stealth, Trek, Ceepo, Wilier, Walser, Ridley... I don't know if they are faster, but it makes my suspicious that these are not included....)