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2006-07-31 5:19 PM

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Subject: Aero Helmet vs. Aero Wheels
Did anyone see the article in Triathlon Magazine about the guys from MIT who race in triathlons but also do research on aerodymanics? I thought the most interesting point from the interview style format of the article was their statement that a triathlete is better off spending $200 on an aero helmet than $2,000 on aero wheels as the difference in drag between a standard helmet and an aero helmet is far greater than the difference in drag between standard wheels and a nice set of aero wheels.

Any of you bikers care to disagree with the authors? Not that I was going out to buy a $2,000 set of wheels but it would be nice to know that the aero helmet makes that much difference.

Thoughts?


2006-07-31 5:23 PM
in reply to: #498724

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Elite
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Subject: RE: Aero Helmet vs. Aero Wheels
I've heard that before, so it must be true
2006-07-31 5:40 PM
in reply to: #498724

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Coach
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Subject: RE: Aero Helmet vs. Aero Wheels

For what I've heard/read it is true... If I can find the article(s) I'll post it later. To be honest I am not sure if I believe it or not. I race with both and even though my times are considerably faster than last year when I wasn't, I think it has to do more with ALL the hrs I've spent on the saddle rather the benefits from one or the other

2006-07-31 5:46 PM
in reply to: #498739

Expert
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Subject: RE: Aero Helmet vs. Aero Wheels
I am going with the science nerds on this one.  It won't take me as long to save for the helmet.
2006-07-31 6:32 PM
in reply to: #498724

Master
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Subject: RE: Aero Helmet vs. Aero Wheels
It was in Bicycling magazine.

There were some pretty interesting things they said. Like wearing gloves creats more drag than a nonaero front wheel.

Of course, they were only accounting for drag and not for weight savings. I don't think it would change it that much, but it could affect the outcome.
2006-07-31 7:44 PM
in reply to: #498724

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Not a Coach
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Subject: RE: Aero Helmet vs. Aero Wheels

From what I've heard about it, this assumes you stay aero the whole time, have a good head position and don't turn your head.  If you look behind you, look down as you reach for a drink, etc., you give up most of the benefit of wearing it.  Basically, in the "real world" outside of a very disciplined time trialist the wheels will end up being a greater benefit. 

But I like the cost saving angle.



2006-07-31 7:51 PM
in reply to: #498724

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Subject: RE: Aero Helmet vs. Aero Wheels
I think I would feel like a bit of a poser with an aero helmet and no aero wheels, just me though, I think you either go all the way or not.

That being said I do have aero bars on my road bike, but more for another comfortable position on long rides.
2006-07-31 8:44 PM
in reply to: #498724

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Resident Curmudgeon
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Subject: RE: Aero Helmet vs. Aero Wheels
Why not have both? Nobody said it was an either/or proposition.
2006-07-31 9:11 PM
in reply to: #498724

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Subject: RE: Aero Helmet vs. Aero Wheels

I haven't seen the article but I have a question as to what they were saying...

 

Is it more cost effective $ for $ or does the $200 helmet give more benefit than the $2,000 wheels?

Thanks!

2006-07-31 9:15 PM
in reply to: #498870

Master
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Subject: RE: Aero Helmet vs. Aero Wheels
crusevegas - 2006-07-31 9:11 PM

I haven't seen the article but I have a question as to what they were saying...

Is it more cost effective $ for $ or does the $200 helmet give more benefit than the $2,000 wheels?

Thanks!



Both.
2006-08-01 6:21 AM
in reply to: #498724

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Subject: RE: Aero Helmet vs. Aero Wheels
I thought it was a one or the other type question.


2006-08-01 9:21 AM
in reply to: #498724

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Veteran
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Subject: RE: Aero Helmet vs. Aero Wheels
I am planning on having both eventually - so that just gives me one more reason to get the helmet that I wanted anyway.

Happy Training
Scott
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2006-08-01 9:51 AM
in reply to: #498724

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Subject: RE: Aero Helmet vs. Aero Wheels
It's certainly a lot cheaper. I'd be interested to see this article becuase from what I've learnt you can gain a lot more from upgrading to top quality aero wheels than doing the same with an aero helmet. The greatest amount of air drag will come from the wheels - switch from a rear aluminium 32 spoke to a disc wheel and there will be a considerabel improvement. Switching from a standard vented helmet to an aero-helmet will just (in most cases) improve(/speed up) the air-flow around the helmet, thats all.

As already mentioned, you have to ensure you keep your head up at all times otherwise your cone-head will have the opposite effect and brake into the wind. I have the Louis Garnea rocket. There's a fair bit of cavity space inside the helmet so although its aero its actually taking up a bigger surface area. I have not noticed any significant changes other than from fitness development. And its also a little heavier.
2006-08-01 10:15 AM
in reply to: #499268

Elite
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Subject: RE: Aero Helmet vs. Aero Wheels

I would like to see this test run outside the wind tunnel.   Sitting in a tunnel with the wind a perfect 0* in front is MUCH different then riding along on varried terrain with wind at different positions to you.

The other thing is that this study is making a comparison to AERO only.  9 times out of 10 when you buy aero race wheels, you are replacing heavier training wheels.  The weight savings alone will account for a lot of speed.

I'd also like to see the diference between the helmet, a deep aero wheel and a shallower aero wheel.

2006-08-01 10:16 AM
in reply to: #499268

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Subject: RE: Aero Helmet vs. Aero Wheels

Daz - 2006-08-01 7:51 AM It's certainly a lot cheaper. I'd be interested to see this article becuase from what I've learnt you can gain a lot more from upgrading to top quality aero wheels than doing the same with an aero helmet. The greatest amount of air drag will come from the wheels - switch from a rear aluminium 32 spoke to a disc wheel and there will be a considerabel improvement. Switching from a standard vented helmet to an aero-helmet will just (in most cases) improve(/speed up) the air-flow around the helmet, thats all. As already mentioned, you have to ensure you keep your head up at all times otherwise your cone-head will have the opposite effect and brake into the wind. I have the Louis Garnea rocket. There's a fair bit of cavity space inside the helmet so although its aero its actually taking up a bigger surface area. I have not noticed any significant changes other than from fitness development. And its also a little heavier.

I thought I learnt somewhere that the rider was the biggest amount of of air drag..

2006-08-01 10:16 AM
in reply to: #498724

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Champion
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Subject: RE: Aero Helmet vs. Aero Wheels
One of the engineering stuents involved in that at MIT was on the Slowtwitch forum and basically said that the article misrepresented the data. No big shock there.

An aero helmet is beneficial IF you can keep your head still. Otherwise that big tail becomes a detriment. Wheels don't care what your head is doing...


2006-08-01 10:18 AM
in reply to: #499308

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Champion
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Subject: RE: Aero Helmet vs. Aero Wheels
crusevegas - 2006-08-01 11:16 AM

Daz - 2006-08-01 7:51 AM It's certainly a lot cheaper. I'd be interested to see this article becuase from what I've learnt you can gain a lot more from upgrading to top quality aero wheels than doing the same with an aero helmet. The greatest amount of air drag will come from the wheels - switch from a rear aluminium 32 spoke to a disc wheel and there will be a considerabel improvement. Switching from a standard vented helmet to an aero-helmet will just (in most cases) improve(/speed up) the air-flow around the helmet, thats all. As already mentioned, you have to ensure you keep your head up at all times otherwise your cone-head will have the opposite effect and brake into the wind. I have the Louis Garnea rocket. There's a fair bit of cavity space inside the helmet so although its aero its actually taking up a bigger surface area. I have not noticed any significant changes other than from fitness development. And its also a little heavier.

I thought I learnt somewhere that the rider was the biggest amount of of air drag..

I resemble that remark...

2006-08-01 10:24 AM
in reply to: #499308

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Subject: RE: Aero Helmet vs. Aero Wheels
crusevegas - 2006-08-01 4:16 PM

Daz - 2006-08-01 7:51 AM It's certainly a lot cheaper. I'd be interested to see this article becuase from what I've learnt you can gain a lot more from upgrading to top quality aero wheels than doing the same with an aero helmet. The greatest amount of air drag will come from the wheels - switch from a rear aluminium 32 spoke to a disc wheel and there will be a considerabel improvement. Switching from a standard vented helmet to an aero-helmet will just (in most cases) improve(/speed up) the air-flow around the helmet, thats all. As already mentioned, you have to ensure you keep your head up at all times otherwise your cone-head will have the opposite effect and brake into the wind. I have the Louis Garnea rocket. There's a fair bit of cavity space inside the helmet so although its aero its actually taking up a bigger surface area. I have not noticed any significant changes other than from fitness development. And its also a little heavier.

I thought I learnt somewhere that the rider was the biggest amount of of air drag..



Lol well I was just thinking about bike components.
2006-08-01 10:25 AM
in reply to: #499318

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Subject: RE: Aero Helmet vs. Aero Wheels
RedCorvette - 2006-08-01 4:18 PM

crusevegas - 2006-08-01 11:16 AM

Daz - 2006-08-01 7:51 AM It's certainly a lot cheaper. I'd be interested to see this article becuase from what I've learnt you can gain a lot more from upgrading to top quality aero wheels than doing the same with an aero helmet. The greatest amount of air drag will come from the wheels - switch from a rear aluminium 32 spoke to a disc wheel and there will be a considerabel improvement. Switching from a standard vented helmet to an aero-helmet will just (in most cases) improve(/speed up) the air-flow around the helmet, thats all. As already mentioned, you have to ensure you keep your head up at all times otherwise your cone-head will have the opposite effect and brake into the wind. I have the Louis Garnea rocket. There's a fair bit of cavity space inside the helmet so although its aero its actually taking up a bigger surface area. I have not noticed any significant changes other than from fitness development. And its also a little heavier.

I thought I learnt somewhere that the rider was the biggest amount of of air drag..

I resemble that remark...



If you can pinch your back with some heavy duty bull-clips you may be able to create the perfect tear-drop body shape
2006-08-01 10:59 AM
in reply to: #499306

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Master
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Subject: RE: Aero Helmet vs. Aero Wheels
vortmax - 2006-08-01 9:15 AM

I would like to see this test run outside the wind tunnel. Sitting in a tunnel with the wind a perfect 0* in front is MUCH different then riding along on varried terrain with wind at different positions to you.

The other thing is that this study is making a comparison to AERO only. 9 times out of 10 when you buy aero race wheels, you are replacing heavier training wheels. The weight savings alone will account for a lot of speed.

I'd also like to see the diference between the helmet, a deep aero wheel and a shallower aero wheel.





I respectfully disagree on the weight issue. Aerodynamics and drag are the main factors hindering higher speed for cyclists, not the weight of their bike or components. I can ride in aerobars on an old 30 lb steel bike and eventually cruise right by you on a 19lb carbon galactic space probe (everything else being equal) if I am in the aero position and you are not.



The total power required to ride a bike is:

1. Power lost to aerodynamic drag: (½rhoCdAVA3)
2. Power loss from rolling resistance of tires: (CRRWTVG)
3. Power to rotate wheels (FwVG3)
4. Power to overcome gravity on a hill (WTVGsin(arctan(RoadGrade)) (varies greatly)
5. Friction losses in the drive and bearings (small except for chain line cross over)
6. Power to accelerate and power losses from deceleration (converted to heat).

Power required = ½rhoCdAVA3 + CRRWTVG + FwVG3 + WTVGSin(Arctan(RoadGrade)

Aerodynamic drag represents the largest resistance while riding over level ground.



Here is a link to a site that is referenced for this very question....I hope that this site will work as a good reference for many of you when comparing wheelsets which are hugely important when looking at areas to improve from standard parts.

http://www.bsn.com/cycling/WheelAerodynamics.html



Here is the text of part of a conversaton I had with an person more familiar with these equations, for the purpose of comparing some Rolf Vector spoked wheels to some Spinergy Rev X carbon race wheels:


"Basically, when looking at drag data, lower is better. Yaw angle is the effective wind angle that results from "combining" your velocity with velocity of any crosswinds (if present). So if you are riding at 20mph and there is a direct crosswind of 5mph, the the effective yaw angle is arctan(5/20) or 14deg (with 0deg being straight ahead). Real world yaw angles tend to be in the 5-15deg range, just as a general off-the-cuff approximation for an average rider. 0deg of yaw would occur only when you are riding in windless conditions (or the very rare direct head/tailwind). Yaw angles are important because they give you an idea how a wheel will perform in real world situations. Some wheels perform very well at yaw angles of ~0deg, and then fall off very noticably as yaw angle increases (the Xentis is the most notable example of this). Most aero wheels, however, will see even more improvement over conventional spoked wheels as yaw angle increases. The disc is the ultimate example of this, with drag dropping to almost 0 at very high yaw angles. So if you look at your RevX, the drag drops as yaw angle increases (probably due to the composite spoke design), whereas the Rolf/Trek wheel increases.

In the simplest terms, though, all you really need to worry about is the fact that the Spinergy RevX has about 30-40% less drag than the Rolf on average."


2006-08-01 11:20 AM
in reply to: #499401

Elite
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Subject: RE: Aero Helmet vs. Aero Wheels

i understand what you are saying completely, and that does hold true for level ground.  What I'm saying is that the test failed to account for the weight variable, so there is at least one parameter that was uncontrolled in the test.  Also, no course is exactly flat.  While it's not as major a concern as aerodynamics, it still is a concern that could make a light set of aero wheels show more improvement over an aero helmet while a similar set of heavier wheels would show to be less effective.

The should have performed the test with a bike in the real world on a non-aero set of wheels and an aero set of wheels of the same weight.



2006-08-01 11:26 AM
in reply to: #499430

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Not a Coach
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Subject: RE: Aero Helmet vs. Aero Wheels
vortmax - 2006-08-01 11:20 AM

The should have performed the test with a bike in the real world on a non-aero set of wheels and an aero set of wheels of the same weight.

Pretty much all the accepted "tests" are done in wind tunnels.  "Real world" tests are nearly impossible to control.  What they tested showed that the drag savings from an aero helmet (assuming stable, good positioning) are greater than for race wheels.

2006-08-01 12:05 PM
in reply to: #498724

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Expert
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Subject: RE: Aero Helmet vs. Aero Wheels
All test results are shown at optimal conditions, whether its for your bike or your car or anything in a wind tunnel. Your cars est miles/gallon test is done in a wind tunnel, windows colsed with no braking, yet people still get cars based on fuel efficiency even if they never get what the company says they will get. This test sayd that an aero helmet will give you a greater aeordynamic advantage than race wheels.

Honestly though, I would just get both, if you are going to shell out 2000 for wheels, whats another 200 for a helmet???

Lets all be fast and aero.
2006-08-01 12:07 PM
in reply to: #498724

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COURT JESTER
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Subject: RE: Aero Helmet vs. Aero Wheels

Remind me NOT to get an aero helmet. 

When my time comes to get thrown from the bike, I want my helmet catching as much wind as possible so it can slow me down more before my head bounces like a superball off of (insert name of surface).  

2006-08-01 12:52 PM
in reply to: #499506

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Master
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Subject: RE: Aero Helmet vs. Aero Wheels
DON"T spend $2k on aero wheels.

I picked up a used set of Spinergy Rev X whels with new tubulars (3) and a 9 speed cassete for $250.00 on Ebay. I also picked up a brand new set of ALX 260's for $50.00 for training wheels.

This sport ddoesn't have to be hella expensive if you can shop a little !
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