Comments on: Are You A Speed-Seeking, Torso-less Pair of Legs?

By: Fishy Marketing : The Slippery Speedplay Mannequin « Cycling

Fishy Marketing : The Slippery Speedplay Mannequin « Cycling — Sun, 17 Jan 2010 07:08:24 +0000

[...] is apparent to others, Speedplay wants you to buy their Zero Pedals which will free you of between 0-0 [...]

By: Ron

Ron — Fri, 27 Nov 2009 09:20:00 +0000

To James above : Could CDA be a mere 0.242? First of all, if that’s the case it can’t be dimensionless so it must be 0.242m^2.

Next, in some papers I have read on wind tunnel testing, the frontal area of a top 180cm 73kg pro cyclist on a bike in aero position was 0.31 m^2. That of the slick TT bike he was riding was 0.11m^2 for a total of 0.42m^2. These numbers were measured by planimetry.

If the CDA in speedplay’s case is to be 0.242, which is much lesser than the frontal area of the above rig in the study, the Cd of the robot must be what?

Let’s make some assumptions. If we take the cyclist I mentioned above and assume that his lower legs have 1/2th the total frontal area, that’s about 0.15m^2. If we assume that the robot legs had a similar looking frontal area and the bike had about 0.11m^2, total area is 0.26m^2 for the half robot and bike. Then the drag co-efficient has to be about 0.93 so that CdA is 0.242.

Is 0.93 big for Cd for a crude figure in the form of a robot’s legs pedaling a bike? For perspective, its 0.78 for a cyclist in racing position. So its possible that you’re right and that Speedplay made a typing mistake.

By: Alien Biker | The missing link, the one piece of gear that will help you finally ride like a pro!

Sat, 14 Nov 2009 16:17:04 +0000

[...] just read a post over at cyclocosm that left me shaking my head and thinking how so many people turn into gear heads because of the [...]

By: Hulkster

Hulkster — Thu, 12 Nov 2009 23:41:58 +0000

isn’t saving 33 seconds per hour some sort of einstein-relativity-advanced-physics thing?

like having two watches set to the same time and having one in an airplane, with the result being that the time moves more slowly for the watch on the plane?

so by using speedplays and going faster, your hour time trial is actually not an hour, but 59:27, according to the theory of relativity. but that would be according to your computer on your bike, which is moving fast. the official’s clock, which is stationary, would still say one hour.

so i guess that is why whenever i time myself in a tt, the time that i get is always better than i see in the official results.

By: Tom

Tom — Wed, 11 Nov 2009 19:39:16 +0000

Awesome, I would have bought the pedals for the >100% reduction in training. Now you tell me I can drink more too!

By: Psychlist

Psychlist — Wed, 11 Nov 2009 00:13:14 +0000

Training an extra 50km and drinking one less beer per week will improve your performance more than their pedals will.

Interesting comment from Andy MJ re weight of cleats. I never thought of it that way.

By: Al

Al — Tue, 10 Nov 2009 03:04:23 +0000

All I know is that my Speedplays (Light Action) likely saved/are saving my knees. CdA be damned.

A nod to Cosmo’s 2nd paragraph. I’m just some Fred who wanted a pair of pedals that felt right and performed well. Do they really need to market themselves as the next aero revolution?

As Christian mentions above, it looks like the model year problem is showing it’s ugly self again.

By: Douglas

Douglas — Tue, 10 Nov 2009 02:53:20 +0000

Other concerns aside (cadence, etc), I really question how well speedplay’s methodology really captures the pedaling motion itself, which I would wager has a drastic impact on pedal aerodynamics. If you watch the video speedplay offers on their site, it reveals that the angle of their model’s ankle changes only very slightly. But… in the real world, many people, especially at upper ends of the sport, pay a lot of attention to training a pedal stroke that scoops through the bottom of the stroke (ankling if you want to use the common term), which often leads to exposing much, much less of the actual pedal body to the wind on the upward half of the pedal stroke as the toe is angled much further downward than assumed. Speedplay’s “advantages” may exist, but they likely only exist during half a normal pedal stroke.

By: Christian

Christian — Tue, 10 Nov 2009 01:29:54 +0000

I’ve ridden Speedplay pedals since about 1994 or so, I’ve owned multiple pair of the X-2 Stainless and X-1 Ti, as well as the CrMo Zeros. I have nothing but love for these pedals. I think entry/exit is probably better on the X series, but the Zeros give you the option of limiting or elimination the float, so there’s that. They really are pretty light, too, even when you include the cleat, which is more plastic than metal.

Having said all of that, the aerodynamic claims are amongst their worst yet. But if your product is relatively unchanged for years, as Speedplay’s is, you have to have something new to crow about, and everyone loves getting more aero lately…

By: James

James — Tue, 10 Nov 2009 00:34:28 +0000

I agree that Speedplay failed to post some useful info in that analysis, such as the shoes used and if the same saddle height was used for both shoe/pedal combinations. However, the 0.237 number is not Cd, but CdA (coefficient of drag * frontal area). Poor choice of words on Speedplay’s part in that caption.

Typical frontal area of a racing cyclist is << 1 m^2, so the CdA tends to be a much lower number than just Cd. In fact, 0.237 is just a so-so number for a whole cyclist in TT position in a wind tunnel, so I suspect that the headless torso actually is not as slippery as a whole person.

Anyhoo, a .006 improvement in CdA will get you about 0.4 Km/h faster on a flat course at 250W. Which, of course, only exists in the analyticcycling.com model that I constructed quickly to get some numbers.