Aero at any speed? True or urban myth? (Page 2)

I don't appreciate such a vicious, personal attack.  How dare you Sir!   Joking of course...

The great thing about physical laws; they're not theory.  They hold true regardless of what our personal biases and anecdotal evidence tell us. 

There's a big difference between talking about cumulative time impact versus talking about how drag increases.  Drag increases exponentially with speed, meaning that at any particular time the faster guy is gaining more drag benefit from aero gear than the slower guy.  However, if the slower guy is on the course longer, they may experience more time savings.  Two very different things, but both true. 

You know, we are allowed to talk about Slowtwich openly here.  Most folks here frequent both sites, and both sites add a lot to the tri community.

If slower riders don't have any aero benefit why does everyone across the board have a signifigant gain riding a tri bike over a roadie? 

I used to think aerodynamics was overratted hodgepodge (sp?) until I changed my position and dropped my stem and had a .5 mph improvement overnight (and I'm slow).

Also, I think the running and road cycling 'cultures' are more geared towards power output and volume of training.  You'll never see a marathon coach tell a guy that he lost x amount of time because he didn't draft for a few miles...

With cycling, half the guys in breakaways are riding on the hoods instead of the drops.

I think both sports will probably become 'aero conscious' in the next 20 years, much like triathlon is now.

I've put together a spreadsheet to run the numbers (I may not be intelligent enough to get it linked into this post). Essentially, the effect of good aero equipment and position vs riding on the hoods of a road bike with road helmet is about 2 mph at 100W, 2.75mph at 200W, 3mph at 250W and 3.5mph at 300W. In an Olympic distance bike of around 25 miles, this accounts for a difference of 8:47 at 100W, 8:12 at 200W, 7:14 at 250W, and 7:22 at 300W. As mentioned above, the effect of higher speed cancels out as the slower rider gains more time over the same distance if comparing purely time gained, but I think anyone would agree that the difference between finishing the oly distance in 85:43 vs 76:55 (roughly 60th percentile vs 40th percentile) is not nearly as significant as the difference between 60:00 and 52:38 (top age grouper or amateur elite vs top professional). As an example, at the Minneapolis Lifetime triathlon, Matty Reed finished in 56:39, while the top amateur finished in 59:11, and the top age grouper was 60:13.  Even from drops on a road bike at 265W to optimized aero, you can go from 60:00 to 54:33, or from drops to clip-on aeros goes from 60:00 to 58:50 (saves over 1 minute!)

I think it simply shows that the aero position can make a huge difference.

Just for laughs -- identical riders (except for power) riding 40k in identical conditions (using made-up but not crazy numbers on analytic cycling -- obviously the details depend on the numbers but the point is clear).  They each ride twice, once reasonably aero and once not very aero.

Lower power, higher CdA:  1:16:01

Lower power, lower CdA:  1:07:00

Time saved for lower power rider: 9:01

Higher power, higher CdA:  1:05:22

Higher power, lower CdA:  57:28

Time saved for higher power rider: 7:54

ETA:  Just saw the post above -- analyticycling.com will save you a lot of trouble!

Certainly would have! However, putting together myself certainly helped me picture it. Looks like a great site.

There may be some more comprehensive links but here are 2 sites that show a cost / benefit chart on aero effect.

http://www.cyclingtipsblog.com/2010/04/biggest-bang-for-your-buck-in-time-trial-equipment/

http://www.sheldonbrown.com/rinard/aero/aerodynamics.htm (Scroll down the the shopping chart).

Basically, you will get bigger bank for your buck from the Helmet.  But aerobars should come before that.

Thanks Fred. I see that this thread is on ST also.

When I'm drafting on the bike, my front tire is within inches (maybe a foot?) from the back of the guy in front of me.  I can usually match my pace with theirs to tuck in close.  The further back I drift, the more wind resistance.  You guys probably know the numbers better than me, but I find that 3-5 feet back I lose a substantial amount of the draft.  Even riding with a total stranger I can usually match pace.  I'm not much faster than 18-20 on my training rides and I feel the benefit (around 5-10bpm lower HR).

Running is a whole different story.  With everyone's cadence / stride length being different, it would be very hard for me to run a long distance 12 inches behind the guy in front of me. I'm getting visions of tripping rather than getting true drafting benefit in most cases.  

Just my non-science, new to tri's opinion ...

just because I'm an engineer and I can't take it anymore, the drag force equation is

 

 

velocity is not cubed!