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Don't Overthink: Aero position ???
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I've been reading through old threads based on "aero position" and related search strings. I ran across the "don't overthink" thread (which I've seen many times before). But, it got me thinking...it would be useful to have a similar compilation of general advice for rider position hints/tips/tweaks to improve overall CdA.

I realize everything aero needs testing to prove it out. So, unlike a lot of the things on the "don't overthing" thread...you can't just follow the advice blindly. I am planning to field test everything I try (vis-a-vis the Platypus thread).

I only acquired a TT bike this year (P3SL), and had a fit done by Tent Nix. I rode that to good success in my races this fall (2nd fastest AG bike split in both races with that bike+Position) on relatively lower watts. But, now that my off-season is here...I'm looking to improve.

I'd like to lay out a testing schedule over the winter, where on good weekend days, I can go over to my testing venue and run a series of tests on one or two changes at a time. So, I'm really looking to compile a list of things to try...specifically body/head/arm/elbow position changes.

Is there a thread already...that I just haven't run across, yet? Or would some of you more aero experienced, be willing to share some thoughts?
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Re: Don't Overthink: Aero position ??? [Tom_hampton] [ In reply to ]
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Assuming an excellent fit by Trent, I wouldn't mess with the fit all that much chasing aero. Once you are proficient at field testing, you could look at elbow width, forearm angle, a couple cms more or less reach, a couple cms more or less drop, helmets, clothing, nutrition placement. That should keep you busy for a few years.
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Re: Don't Overthink: Aero position ??? [Tom_hampton] [ In reply to ]
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Nice thought. That I am in no way qualifited to answer.
But if I tried (because of course I will, thank you Dunning, Kruger and all the wise people here), it would be something like:

  • Learn how to use a tape measure and trigonometry, and understand Pad X/Y and orthodoxy.
  • set up a video camera perpendicular to your bike trainer (because of course you have one), above the bottom bracket and about level with your hips. (By law it must be on the chain side)
  • Get a saddle that allows you to rotate your pelvis forwards. If you are unsure what to get, ISM PN 3.0 or 3.1
  • set your saddle height, so that your knee angle at the bottom is appropriate. Not overreached, not rocking hips or pointing toes excessively. Too high is bad, too low is not so bad.
  • Set your extensions so when you grip the bars your elbows are in the elbow pads, not (a long way) behind them.
  • Angle your extensions up somewhat. Not flat, not down.
  • Figure out your elbow pad drop from the saddle height based on Slowman's old formula, and set your Pad Y based on that
  • Set your Pad X so that your elbows and shoulders are a little over 90 degrees.
  • Set your saddle fore-aft so you're sitting comfortably on the correct part of it.
  • Review your hip angle at the top of the pedal stroke. If it's too tight, look at shorter cranks.


After that it probably gets more user-specific, but I would guess the following are generally true:
  • turtle your head and shrug your shoulders
  • use a helmet that sits on your back. If unsure, Gira Advantage 2, Bell Javelin or Giro Aerohead
  • Narrow your elbows
  • size down your clothing. Wrinkles bad


Then finally
  • Post your video to ST and get expert review.
Feel free to pick this apart, I'm not precious

Of course the money-no-object answer is: buy a P5, fly your favourite fitter in your private helicopter to the nearest wind tunnel and go nuts.
Last edited by: MattyK: Oct 25, 18 14:09
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Re: Don't Overthink: Aero position ??? [MattyK] [ In reply to ]
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Helicopter is in the shop, damnit!

I should have prefaced this with, "assuming you already have a quality fit..." I think your first section of bullet points is really just about getting an orthodox bike fit. But, just because you have an orthodox fit, and decent equipment doesn't mean your CdA is 0.19...or even sub-0.25.

So, I was really wondering about the list of smaller tweaks that make/break your CdA, once you already have a position that's "pretty close".

That video(s) that was posted this morning from AeroCoach helped clear up several things for me (I think). Although, I wish they would have shown more footage of the riders as changes were being made. Much of that is what your second grouping gets at...along with Dave's list above. So far its sounding like:

1. Elbow width (mostly more narrow)
2. Forearm angle (mostly more up)
3. Reach (could be more or less)
4. Drop (could be more or less)
5. turtle head (to keep it in front of the shoulders/torso as much as possible).
6. Helmet tail on back.
7. keep knees in close to frame while pedaling.
8. Keep feet mostly neutral (not a toe down pedaling style)
9. Skin is slow, hair is slower.
10. Shoulder wrinkles are slow.

Much of the idea seems to be to create as gradual (and narrow) of a flow separation path as possible. In simplistic terms, higher hands divide the air before it gets to the head, the head divides the air before it gets to the shoulders, and the shoulders for the torso.

If the top of the helmet is above the torso, then that portion of the helmet is increasing the total cross sectional area. So, anything that allows you to get the top of the helmet lower or even with the highest point of the torso will reduce the overall area.

Adjusting reach may allow a better shrug (for narrower shoulders), and/or a lower head position.
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Re: Don't Overthink: Aero position ??? [FindinFreestyle] [ In reply to ]
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Thanks.

I wouldn't make any permanent changes without discussing with Trent and a potential for a new fit session. This was more about a hunt for things that might make a significant, positive difference. Ultimately, I would take those field results back to Trent for a wholistic assessment of fit. I envision the conversation being something like, "I found changes X,Y,Z improved my CdA from 0.xxx to 0.yyy. How can we change the fit to make that 'ride-able' for D duration?"
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Re: Don't Overthink: Aero position ??? [Tom_hampton] [ In reply to ]
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Tom_hampton wrote:
I should have prefaced this with, "assuming you already have a quality fit..." I think your first section of bullet points is really just about getting an orthodox bike fit.

For many people I think that's too big an assumption to start with :D Given that your body position is the cause of most of the drag it's not something you can brush past. I was just trying to distil a number of the articles and forum threads into a simple list. Sorry if I derail your post...

My point I guess was that getting yourself to an orthodox position doesn't necessarily need to involve visiting an expert fitter. Just working out from orthodoxy what a good orthodox position for your body size is, and knowing trigonometry, you can often dial in a pretty good position with no more than the adjustments on your bike, or at the most a new stem and saddle.
Last edited by: MattyK: Oct 25, 18 15:00
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Re: Don't Overthink: Aero position ??? [Tom_hampton] [ In reply to ]
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Tom_hampton wrote:
If the top of the helmet is above the torso, then that portion of the helmet is increasing the total cross sectional area. So, anything that allows you to get the top of the helmet lower or even with the highest point of the torso will reduce the overall area.

While that's true, it may be the case that decreasing A can have a countervailing effect on Cd. An interesting case is about mantis: mantis doesn't really affect A much but it can have an effect on Cd -- and also possible effects on other parameters that may affect power. All in all, what you want to do is maximize watts/CdA, not just maximize the the numerator or minimize the denominator (or part of the denominator).
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Re: Don't Overthink: Aero position ??? [RChung] [ In reply to ]
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RChung wrote:
Tom_hampton wrote:

All in all, what you want to do is maximize watts/CdA, not just maximize the the numerator or minimize the denominator (or part of the denominator).

Bless you, Robert Chung.

Jim Manton / ERO Sports
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Re: Don't Overthink: Aero position ??? [RChung] [ In reply to ]
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RChung wrote:
Tom_hampton wrote:
If the top of the helmet is above the torso, then that portion of the helmet is increasing the total cross sectional area. So, anything that allows you to get the top of the helmet lower or even with the highest point of the torso will reduce the overall area.

While that's true, it may be the case that decreasing A can have a countervailing effect on Cd. An interesting case is about mantis: mantis doesn't really affect A much but it can have an effect on Cd -- and also possible effects on other parameters that may affect power. All in all, what you want to do is maximize watts/CdA, not just maximize the the numerator or minimize the denominator (or part of the denominator).

Thank you. Yes that all makes perfect sense.
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Re: Don't Overthink: Aero position ??? [Tom_hampton] [ In reply to ]
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It seems your fit is good, so my first recommendation would be to NOT screw that up. There are a ton of little tips that can make your current setup faster. The new Aerocoach videos by James Cabe (I think) and referenced in another current thread give a ton of simple tricks and ideas for minor position tweaks and gear choices.
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Re: Don't Overthink: Aero position ??? [Tom_hampton] [ In reply to ]
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I've done a ton of testing on lots of people now (but way less than Jim of course) and the more I test the more I've learned that it's complicated. I think I probably could have given you a nice list of things to try a couple years ago, but now I find it much harder :-) That said, here's a loose list:


(1) The most important things are your head and shoulders and knees. Knees have to be in. Shoulders have to be narrow. Head has to be low.


(2) Don't do anything that significantly compromises your power.
  • I think a lot of people start by chasing aero and sacrificing power. They may get a bit faster in this process, but if you want to be really fast you have to have both. Test both aero *and* power constantly. Don't chase one without the other.

(3) You almost always need to move more than one thing at a time.
  • People are always saying to test this or that (forearm angle or bar height or elbow width or whatever) but I've found that if you move one thing, you almost always have to move something else too. Best example: I must have tried "high hands" 20 different times on several different riders. Each time it was slower than flat arms. Then one day I asked "suppose my hands were high, where would my elbows need to be for it to be comfortable and make my shoulders small". Boom, huge improvement.

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Re: Don't Overthink: Aero position ??? [lanierb] [ In reply to ]
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lanierb wrote:
People are always saying to test this or that (forearm angle or bar height or elbow width or whatever) but I've found that if you move one thing, you almost always have to move something else too. Best example: I must have tried "high hands" 20 different times on several different riders. Each time it was slower than flat arms. Then one day I asked "suppose my hands were high, where would my elbows need to be for it to be comfortable and make my shoulders small". Boom, huge improvement.

this nugget basically summarizes my fit entire philosophy... it follows the knowledge hierarchy of data, information, knowledge, understanding. Most people don't *understand*... they just think they know or worse yet merely have information that higher hands may be faster. They just don't know what they don't know...

Eric Reid AeroFit | Instagram Portfolio
Aerodynamic Retul Bike Fitting

“You are experiencing the criminal coverup of a foreign backed fascist hostile takeover of a mafia shakedown of an authoritarian religious slow motion coup. Persuade people to vote for Democracy.”
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Re: Don't Overthink: Aero position ??? [lanierb] [ In reply to ]
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lanierb wrote:
I've done a ton of testing on lots of people now (but way less than Jim of course) and the more I test the more I've learned that it's complicated. I think I probably could have given you a nice list of things to try a couple years ago, but now I find it much harder :-) That said, here's a loose list:


(1) The most important things are your head and shoulders and knees. Knees have to be in. Shoulders have to be narrow. Head has to be low.


(2) Don't do anything that significantly compromises your power.
  • I think a lot of people start by chasing aero and sacrificing power. They may get a bit faster in this process, but if you want to be really fast you have to have both. Test both aero *and* power constantly. Don't chase one without the other.

(3) You almost always need to move more than one thing at a time.
  • People are always saying to test this or that (forearm angle or bar height or elbow width or whatever) but I've found that if you move one thing, you almost always have to move something else too. Best example: I must have tried "high hands" 20 different times on several different riders. Each time it was slower than flat arms. Then one day I asked "suppose my hands were high, where would my elbows need to be for it to be comfortable and make my shoulders small". Boom, huge improvement.


This is so good.

To your point #1, if you had included "elbows" at the end you could've summarized as: "Head, shoulders, knees, elbows -- knees, elbows."
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