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Discussion Starter · #1 ·
I was talking with a friend last night and he said the aero position would help more than an aero bike, an aero helment, etc. combined. What's the quantified advantage of this position?
 

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I believe aero bars are the single greatest advantage if your starting point is a standard road race bicycle. Second is probably a disc wheel.

The aero bar will only work if you put it in an aero position. I crack up whenever I see someone ride 'aero' and their body is more upright than if they were in the hoods.
 

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RHRoop said:
I crack up whenever I see someone ride 'aero' and their body is more upright than if they were in the hoods.
Realizing that some may have physical inhibitors, but it still gets me when I see others who have added clip-on aerobars to comfort/hybrid/mountain bikes. Often times these bikes have 73-degree or greater high-rise stems and the result is an upright, non-aero, inefficient, and possibly even very uncomfortable riding position.
 

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That sounds about right. From what I've read, you really only get the benefits of an areo frame, helmet, etc at higher speeds: say >24 mph or so. Therefore, all that cool stuff is only really worth the cash if you're either fast enough to maintain that speed durring the bike portion of a tri (I'm not), or doing a time trial.
My personal opinion in that it would your money better spent on a professional fitting. If you're not comfortable in an aero position, you won's stay on 'em for the duration of the race and you might as well be on a road bike.All that other crap is just eye candy (unless you're really fast).
 

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dr pabst said:
That sounds about right. From what I've read, you really only get the benefits of an areo frame, helmet, etc at higher speeds: say >24 mph or so. Therefore, all that cool stuff is only really worth the cash if you're either fast enough to maintain that speed durring the bike portion of a tri (I'm not), or doing a time trial.
My personal opinion in that it would your money better spent on a professional fitting. If you're not comfortable in an aero position, you won's stay on 'em for the duration of the race and you might as well be on a road bike.All that other crap is just eye candy (unless you're really fast).

Oops. Sorry about the terrible grammar.
 

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ms6073 said:
Realizing that some may have physical inhibitors, but it still gets me when I see others who have added clip-on aerobars to comfort/hybrid/mountain bikes. Often times these bikes have 73-degree or greater high-rise stems and the result is an upright, non-aero, inefficient, and possibly even very uncomfortable riding position.
Once the owners friend came by the shop and employee purchased a Bianchi 928. He was a crappy triathlete, but couldn't resist a good deal on the bike. After we built up the bike, he brought in a set of tacky aerobars. I tried to convince him that such bars should be left off classy bike, but he told me they were 'worth at least 2-3 mph'. Yeah, 2-3 mph at pro speeds with a proper fitting.
 

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Discussion Starter · #8 ·
dr pabst said:
That sounds about right. From what I've read, you really only get the benefits of an areo frame, helmet, etc at higher speeds: say >24 mph or so. Therefore, all that cool stuff is only really worth the cash if you're either fast enough to maintain that speed durring the bike portion of a tri (I'm not), or doing a time trial.
My personal opinion in that it would your money better spent on a professional fitting. If you're not comfortable in an aero position, you won's stay on 'em for the duration of the race and you might as well be on a road bike.All that other crap is just eye candy (unless you're really fast).
That's a good suggestion. I was fit by a local bike shop and still can't conceive of being in the aero position. Looks painful to the genitalia. Whether I was 'professionally' fit or not I don't know. Cost ~$100. Does that sound professional? I've seen a couple shots of pro cyclists and it looks like they easily fall into the drops. I extend into the drops and usually feel so uncomfortable I don't notice improved stability, which seems to be in contrast to what I've heard on RBR.
 

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Davis69 said:
That's a good suggestion. I was fit by a local bike shop and still can't conceive of being in the aero position. Looks painful to the genitalia. Whether I was 'professionally' fit or not I don't know. Cost ~$100. Does that sound professional? I've seen a couple shots of pro cyclists and it looks like they easily fall into the drops. I extend into the drops and usually feel so uncomfortable I don't notice improved stability, which seems to be in contrast to what I've heard on RBR.
My understanding has always been that you're upper arms should be at about a 90 degree angle, not 'stretched out.' That having been said, I'm not a bike fitter, just some dude with a few triathlon saesons under his belt.

Remeber that getting used to riding in that position can take a while to get comfortable, even with a proper fit. I usually get some back and neck soreness/stiffness for the first couple of rides each spring as I hang up the road bike and start training on my tri bike. Your weight is gonna be on your perenium rather than your ischial tuberosities (like on a road bike), so that can also cause some discomfort too. I use a triathlon specific saddle, which has a more padded nose.
 

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dr pabst said:
From what I've read, you really only get the benefits of an areo frame, helmet, etc at higher speeds: say >24 mph or so.
That is absolutely incorrect.

There is no magic speed where physics turns on. The range of speeds over which people ride is so small that there is no difference in the aerodynamics from the slowest speeds, ~6 mph, to the fastest, ~60 mph. As was mentioned above, slower riders save more time with aero equipment than faster ones.
 

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Discussion Starter · #12 ·
asgelle said:
That is absolutely incorrect.

There is no magic speed where physics turns on. The range of speeds over which people ride is so small that there is no difference in the aerodynamics from the slowest speeds, ~6 mph, to the fastest, ~60 mph. As was mentioned above, slower riders save more time with aero equipment than faster ones.
Really? Time and time again people tell me that if you get aero wheels you won't notice the effect until 25+ mph. Maybe physics is on, just the magnitude of the effect isn't noticeable.
 

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Davis69 said:
Really? Time and time again people tell me that if you get aero wheels you won't notice the effect until 25+ mph. Maybe physics is on, just the magnitude of the effect isn't noticeable.
I don't know about what is or isn't noticeable. The difference in speed between the best and worst wheels is around 1/2 mph for most riders. That's a lot for time trials and other timed events. For just riding around or in a group, where the effect will be less, who's to say.
 

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I've got aero bars on my Raliegh road bike. I'm no speed demon as of yet but they do help when confronted with a headwind. They also help to keep me relaxed as it adds another position to be able to go to for extended rides...
 

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i recently put bought a set of clip on's and they seem to help. they seem to make a big difference for me on down hills and in head winds. (anecdote alert) i hit a new high speed on this hill i always try to go really fast down; 30.6mph up from 29.2mph. that was in the aero position (which still needs a litttle refining) vs. in the drops.
 

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ms6073 said:
Realizing that some may have physical inhibitors, but it still gets me when I see others who have added clip-on aerobars to comfort/hybrid/mountain bikes. Often times these bikes have 73-degree or greater high-rise stems and the result is an upright, non-aero, inefficient, and possibly even very uncomfortable riding position.
Touring cyclists often use clip-ons for comfort, with aerodynamics as a secondary concern.
 

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asgelle said:
The range of speeds over which people ride is so small that there is no difference in the aerodynamics from the slowest speeds, ~6 mph, to the fastest, ~60 mph.
Drag force is proportional to the square of velocity, so your example give a 100-fold difference. The power required to move through the air is proportional to the cube of velocity, a 1000-fold difference.

AFAIK there is no hard threshold, but aerodynamics definitely play a more important role at higher speeds.
 

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Davis69 said:
I was talking with a friend last night and he said the aero position would help more than an aero bike, an aero helment, etc. combined. What's the quantified advantage of this position?
http://www.cervelo.com/content.aspx?m=Engineering&i=Aerodynamics

The cycling power required for any velocity can be predicted based on a mathematical equation. In general, the slower the rider, the more improvement he/she can expect from improved aerodynamics. The main take-home message to be learned from this discussion is that the biggest changes in aerodynamic drag and in cycling performance come from changes in body position, which can improve 40k time by over 6 minutes. An excellent position on a regular bike with regular wheels will allow you to out perform a rider with a typical position on an aero bike with aero wheels by 3 to 4 minutes. Aero wheels can reduce drag by about 0.4 lb. and will reduce your 40k time by about 1 to 2 minutes. An aero frame can reduce drag an additional 0.3 lb. and save you about an additional minute. The effects of bicycle weight, even on a tough climbing course are minimal compared with the effects of aerodynamics. Finally, windy conditions slow you down because you spend more time in the headwind than you do in the tailwind, and consequently, the effects of headwind and tailwind don't ‘average out’.
 

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pretender said:
Drag force is proportional to the square of velocity, so your example give a 100-fold difference. The power required to move through the air is proportional to the cube of velocity, a 1000-fold difference.
Which as we know is totally irrelevant. The range of cycling speeds produces Reynolds number in the range 10^5-10^6. In this range, there are no significant transitions such as laminar to turbulent so the aerodynamics does not change over that range. More specifically, aero equipment affects frontal area, A, and drag coefficient, Cd in the quadratic equation you refer to:

F = 1/2 rho Cd A v^2

Obviously frontal area does not depend on speed. The other term affected by equipment, Cd, does depend on speed over the range of Reynolds number from 1 to 10^8 or higher, but over the small range of speeds people cycle, Cd is essentially constant.

Hence, the statement that there is no difference in the aerodynamics. You'll note I never said force or power was constant.
 
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