Aero vs light wheels

[mellowJohnny]

Road Bike Action headed to a wind tunnel in their latest issue (April) - it's a decent read. Biggest surprise? Aero frames loose almost all their advantage vs. "non-aero" in their tests when a rider was added.

And riding "two up" makes both riders slower.

[HammerTime2]

I'd like to see the details of the wind tunnel test which shows riding two up makes both riders slower. Is that in comparison to riding by themselves? If so, that's a surprising result to me. On the other hand, if the claim is that riding two up is slower than one behind the other, that would be easier to believe.

[Causidicus]

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[MarkTwain]

Having read this topic it has got a little lively at times. Today I managed 118.5 miles @ 18.6mph average (solo). I am using an early 90's steel sannino frame - not aero but I do have some 50mm deep carbon wheels on it (it is the raace bike). If I want to go faster I need to continue training and improve the power output I can sustain. Getting a modern aero frame that is stiffer is not going to make a bigger difference than more training.

Which is as trite and pointless as telling someone to take a sh!t before a ride instead of worrying about a frame that's 200g lighter than another...

[Causidicus]

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[MarkTwain]

You're looking to bring a post, from another thread, in to here?

Why not reply in that thread? Unless you're intent on trolling...a poor one at that.

Ignoring the fact also that the Brim Brothers power meter has been promised for years and they are still sending out assurances that "it's coming" to prevent consumers looking elsewhere (read: ticks all the boxes for 'vapourware').

[Causidicus]

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[MarkTwain]

Pointless: replying to another post in an another thread.

My post was otherwise to temper the users who (and you only have to go back a few pages) state that they are going to 'hold out for it'.

Hell, the whole thread is littered with people who have held out for Brim Brothers. There's nothing trite or pointless on calling out a company making plays to tie up consumer money - when they could be on something else and enoying the benefits of riding with power.


Now, back to aero vs light wheels. You got any further issues, PM or (at risk of sounding trite) at least reply to me in the relevant thread.

[Causidicus]

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[MarkTwain]

Coming from the man who gives replies like this...

viewtopic.php?f=3&t=123633&p=1053624#p1053624

Keep up the good work and keeping those double standards high.

[Tinea Pedis]

Enough.

Back on topic.

[Causidicus]

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[NealH]

I'd like to see the details of the wind tunnel test which shows riding two up makes both riders slower. Is that in comparison to riding by themselves? If so, that's a surprising result to me. On the other hand, if the claim is that riding two up is slower than one behind the other, that would be easier to believe.

Two cars running side by side are slightly slower than a single car, assuming the same output power. The dynamics of air flow creates a lower pressure between the cars which works increase the drag slightly. Probably the same principle with two bikes, just less of an effect.

[mellowJohnny]

I'd like to see the details of the wind tunnel test which shows riding two up makes both riders slower. Is that in comparison to riding by themselves? If so, that's a surprising result to me. On the other hand, if the claim is that riding two up is slower than one behind the other, that would be easier to believe.

Two cars running side by side are slightly slower than a single car, assuming the same output power. The dynamics of air flow creates a lower pressure between the cars which works increase the drag slightly. Probably the same principle with two bikes, just less of an effect.

Yes, that was essentially the gist of it. Note this was observed by the good folks at Alphamantis who do their aero testing on a track.

From p.64 of the April issue of Road Bike Action:

"For the drafting test, Dr. Edwards remained in his regular road position, hands on hoods, and was joined on the track by Nate Koch, a top U.S. pro track racer. Riding at a constant velocity just behind Koch, Dr. Edwards recorded an average CdA of 0.200. This was a CdA of 0.095 lower than riding alone, resulting in a savings of 95 watts when riding at 30 mph. Next, Dr. Edwards and Koch rode side by side, which yielded some surprising results. Dr. Edwards recorded an average CdA of 0.324, or 0.029 higher than riding alone.

“Side-by-side riding doesn’t have the cyclists share any of the low-pressure region behind each rider,” explains Froncioni. “Each individual has his own low-pressure zone pulling him backwards. In addition, the flow of air is forced around a wider frontal area, which leads to an even bigger low-pressure zone behind them.”

[HammerTime2]

Interesting. Now consider the following scenario, which perhaps led me astray.

Case A) Assume 4 riders all with the same power output and aero losses when riding by themselves. Have them ride 2 across and 2 deep, so the same scenario as tested by the magazine, but with each lead rider having someone behind.

Case B) Same as case A, except there are only 2 riders, with one in front of the other.

I thought that case A should be faster than case B. And a case with 3 across, each with a lead and follower should be even faster. Is that correct? Perhaps the side by side riders need to be close enough together to get a favorable effect? I thought that, assuming there is a fixed number of riders behind each lead rider, the more riders across, the faster, because it was making the air go around (outside) the riders, in addition to over the top. But maybe that's not always (or ever?) true? On the other hand, as I suggested above, perhaps more side by side riders helps as long as there is at least one row of riders behind?

Anyhow, I'm pretty damn sure, that except when there is a very large net tailwind relative to the bicycle speed, that a rider A can ride faster if there is an equally capable rider B drafting rider A, than if rider A rides by him(her)self, even if rider A is in front the whole time. In other words, even though a wheelsucker gets more advantage than the rider whose wheel is being sucked, a rider can go faster with a capable rider sucking his(her) wheel than (s)he can ride by him(her)self.