I don't spoon feed.

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"One Line Robert"

I don't really care.

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Make Inside Out Sports your next online tri shop! http://www.insideoutsports.com/

You CLEARLY do care. You won't stop posting and participating in threads. You do realize that the ENTIRE industry publishes in grams and not cda values, right? You "don't care" so much that it's become alarming how much you do care.

Do you just follow me around to comment on my posts?

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Make Inside Out Sports your next online tri shop! http://www.insideoutsports.com/

So, can someone just tell me if this test confirms that I can go back to buying my bike based on price, color and style?

Oh, ha. Thank you for explaining this to me; I didn't realize that's what Brooks was saying.

So yeah, let me clarify: this isn't for the Global Institute of Aeronautical Study Quarterly Journal...or whatever. It's not for academia. This is for regular people. In my opinion, it's the same audience that is reading Trek's or Cervelo's 'White Papers', except it's done by people who don't have a dog in the fight and with greater transparency. I think we can draw a comparison to Flo's tire study, except that this is about bikes.

Personally, I'll be basing my next purchase on the results of this test.

I can't afford to waste time training to overcome the incremental grams of drag/CdA delta between these bikes; running my dental practice and commenting on ST posts about aero gains takes up too much of my free time. The only way I can get any faster is by buying the fastest bike. I just hope the results are out so that I can test ride my new whip before IM LP!

I just "calls 'em as I sees 'em" ;-)

Yeah, some of the problems with using "grams of drag" as a reporting value are that most either don't ALSO include the explanations of "when measured at 30 mph" for the grams value, and also "when traveling at a wide range of race speeds" for the roughly equivalent watts and secs/km translations...or, if they are included, people don't see them or understand them, or just simply forget or ignore them...which invariably leads to the question like Stevej made. I've seen it happen too many times to count.

Not to mention that the original ROT used 0.1 lbs as the drag force value, and using 50g as the equivalent introduces an additional ~10% error (since 0.1 lbs is actually 45.5g)

I understand the desire to "simplify" the results for a wider audience, but after observing this a bunch, I don't think grams of drag is the best way to do that. It adds more confusion and uncertainty than it takes away.

IMHO, Specialized is doing it the most "right"...publish the drag chart in CdA (perhaps include the simple explanation that 0.01 of CdA ~= 10W ~= 1s/km) and then report an overall, yaw- weighted predicted time savings over 40K. Boom. Done.

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http://bikeblather.blogspot.com/

I'm sorry you wasted the time to create a parody account. Let's try and guess which forum member this might be?

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Make Inside Out Sports your next online tri shop! http://www.insideoutsports.com/

I'm with you on this. And as SBRcoffee said in post #91, most triathletes who will look at the results just want to see a comparative chart showing which bike has less drag. They don't really care about the numbers beyond perhaps wanting to convert them into seconds per 40km/56m/112m, and that can be done just as, or more easily using CdA.

The Flo tire study gave both charts, grams and CdA. Both charts look identical, so if a relative layman is just looking to see which bike/tire has less drag visually on the chart, they don't really care what the y axis scale is. They just want the data presented as a visual. Given that, you might as well make the unit CdA imo.

Specialized is doing this the right way? If I recall correctly, in their most recent report, they left the units off the axis entirely, and didn't even tell us what the grid lines represented so we could judge on a relative basis. I might as well just leave it blank like I did in the OP and then put a big arrow facing downwards that says "FASTER". Because that's what Specialized does.

I recognize that the aero benefits of helmets and clothing are dependent on the user and how well they fit. Assuming same setup, are the aero benefots of these bikes rider dependent at all?

There is no aero benefit from one bike or another that's going to justify riding a bike that doesn't fit you, if that's what you're asking. The bike only represents about 20% of the drag in the entire system, so it makes much more sense to optimize the aerodynamics (and comfort and sustainability and all that) of your fit and position on the bike than it does for the bike itself.

All that said, these bikes all fit me and fit me well in a standard configuration. I'm pretty much at the bottom of the stack envelope for all of them, and we didn't have to do anything crazy to them to make them work. We used 5mm of spacers here and there and moved the cups 1cm or so fore and aft to bring things into alignment, but that's about it. Those who have done and do serious comparative bike testing tend to set up their test equipment in lower stack configurations with a rider or mannequin that fits well on the bike. There is plenty we can pick on Cervelo for in the P5-X testing, but appropriate size/fit of the equipment to their mannequin is not one of them.

Are the results from these kinds of tests individual? Yes. Interactions occur everywhere between bike and rider. There will always be some differences aerodynamically. But, I think if you execute this kind of testing in a world-class tunnel like A2 or LSWT (with proven repeatability) on a slate of bikes that fit your rider or mannequin and appropriately normalize all the variables you can, then the results you get will apply quite broadly.

For the rest of us who are engineering challenged. I'm assuming 6 has the most drag and therefore is the slowest while 1 is the fastest?

That's right. The y axis is drag. So higher is slower along that axis, while lower is faster. 1 is the fastest bike here.

Should have put the caveat this assumes the bike fits properly. Thanks for the explanation. I'm on a P3C and looking to upgrade in next six months so this will be very helpful.

Since, for the specific test conditions, CdA and grams of drag are directly proportional a simple solution would be to put 2 y-axes so the reader can read the chart in his/her preferred way.

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Ale Martinez
www.amtriathlon.com

Hello Ale Martinez and All,

Too easy .................. and spoils lots of back and forth posting ..............

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Cheers, Neal

+1 mph Faster

This teasing and subsequent inevitable slowtwich reality TV are just too sad. I don't even care about these results anymore. Publish them or don't.

the flow study is good for most people and if i remember correctly it includes ,watts , cda graphs and timesaving table in one report
so there is something for everybody ;-)
but i guess its either cda or time saving as somebody that dosnt understand cda likely dosnt understand watts either and just wants to see how much time they save.

Thanks for doing this, and putting up with the haters.

That said, I'm sure that Specialized is going to release their Shiv140.6X in a couple of months and it will be the "fastest bike ever" "designed in the WinTunnel" and beat whatever you put at the bottom of the graph, using their own test protocols.

Then the debate will continue.

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'It never gets easier, you just get crazier.'

6 is so asymetric that I'm guessing it's the Ventum. Which is a pity, because it's not a bare frame, it's a bike with 1.4l incorporated (but no other integration yet - why they don't split the box for repair kit and solids is beyond me, but might relate to patents). I hope I'm wrong.

1 is probably the P5-6, in which case I hope nobody reads this because I'd like to get a second-hand one and they haven't reached affordability yet. That bike is like the Porsche 911 of triathlon.

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'It never gets easier, you just get crazier.'

Showboater!

YES!!!

CdA is the only sensible way to present drag data. Fine, if you think that people won't understand it, also present the data in another form. Or 10 different forms. But CdA is the only one that is free of numerous caveats and fudge factors.

I think the public has mostly been *made* ignorant of CdA by it's lack of use.

BTW, I also believe the "time savings" is the best value to report in addition to CdA, because it is less sensitive to assumptions than watts or grams.