Login required to started new threads

Login required to post replies

Prev Next
Narrow vs. Wide arm position
Quote | Reply
In team pursuit events on the track it seems that riders often adopt a wide arm position vs. narrow. How often is this aerodynamically advantageous? Or, does the event or the environment change the dynamics of the drag situations faced?



Quote Reply
Re: Narrow vs. Wide arm position [Louie Cayedito] [ In reply to ]
Quote | Reply
I believe John Cobb had some data where he showed that as long as the elbow are not wider than the waist and the hands are close together to push the air around the elbows and waist, then you still get good laminar airflow. You could do field tests riding up to the top of a hill and see what terminal velocity you hit with various hand and elbow pad positions independent of power output.
Quote Reply
Re: Narrow vs. Wide arm position [Louie Cayedito] [ In reply to ]
Quote | Reply
Team pursuiters need to ride very close and navigate the turns, so a slightly wider stance is worth it if it helps you draft a bit tighter. This is not an issue on the road, which is why most road TT guys have a narrower hand position. As far as arm width, try to have the upper arms shielding your quads (see examples below).





__________________________________________________
Powered by: Hat Tip - the power of thanks
http://hattip.com http://locations.hattip.com
Quote Reply
Re: Narrow vs. Wide arm position [Louie Cayedito] [ In reply to ]
Quote | Reply
Just a couple thoughts...in team pursuit you're in the draft ~75% of the time, so aero could be marginally less important relative to other factors relative to IP or TT.

...and the power output for TP is large. 600W+ in lead position. Possible that wide arms might be beneficial while generating 600+W - more leverage on the lateral motion of the bike. Just guessing. I don't know.
Quote Reply
Re: Narrow vs. Wide arm position [Louie Cayedito] [ In reply to ]
Quote | Reply
Louie Cayedito wrote:
In team pursuit events on the track it seems that riders often adopt a wide arm position vs. narrow. How often is this aerodynamically advantageous? Or, does the event or the environment change the dynamics of the drag situations faced?
In regards to whether there is an aerodynamic advantage, the correct answer is "it depends".

For triathlon, some riders find a wider armpad position (or armpads that rotate) are essential to sustaining the aero position. A narrow position often causes shoulder fatigue and discomfort or neck/trapezius fatigue and discomfort, and consequently the rider sits up to alleviate that tension. I'm of the opinion that, for most triathlon distances, if you have to get up once to stretch your neck and shoulders, it likely offsets any benefits a narrow armpad and extension position can provide.

Additionally, if a wider position allows you a lower cockpit position (a more "aggressive" position, that is), the smaller surface area presented to the wind is typically aerodynamically superior to a narrow armpad position as well.

When evaluating aerodynamics, you've got three components to consider:
  • surface area
  • surface texture
  • surface shape

Surface area is the "eyeball" aero test. It's reasonable to think smaller surface areas are aerodynamically superior to larger surface areas. Surface texture is where smooth surfaces, speedsuits, aero helmets, shaved legs, etc. comes in. It's harder to identify what's best, but the basics are easy to analyze (e.g. shaved legs are better than unshaved legs, speedsuits are better than jerseys, aero helmets are better than basic road helmets, etc.).


Evaluating the benefits of shape, which a narrow armpad position affects, is much more complicated to analyze. CFDs and wind tunnels are essential to identifying which shapes are better than others, whether you are talking about wheel shapes, posture differences, etc.

Trent Nix
Tri Shop - Plano, Texas
http://www.trishop.com
Facebook | Twitter | Instagram | Youtube
F.I.S.T. Advanced Certified Fitter | Retul Master Certified Fitter
Quote Reply
Re: Narrow vs. Wide arm position [trentnix] [ In reply to ]
Quote | Reply
That is helpful, thank you.

I started thinking about this while watching the 2006 Ironman Hawaii bike segment. The announcers said that Normann Stadler had a very fast position in the wind tunnel compared to the other athletes at the time. It was interesting because his position is unlike the narrow arm, high-handed position that is frequently sought after. It looks comfortable.


It seems that some other top-level professionals have bike positions that would not seem to be very aerodynamic (like Brent McMahon, below). Given that one's fastest position is highly individual (and the effects of shape is hard to predict), does it make sense to seek an aggressive but somewhat uncomfortable position? Is the efficacy of making position adjustments to improve aerodynamics purely speculation in the absence of testing?


Quote Reply
Re: Narrow vs. Wide arm position [Louie Cayedito] [ In reply to ]
Quote | Reply
I have heard first hand from a professional cyclist with a very impressive TT resume that wind tunnel testing seemed to indicate the the best arm width was approximately similar to thigh width, perhaps because the arms seem to 'cut' the oncoming air flow for the legs. So, larger thighs, spaced far apart means wider armrests are optimal. And narrower thighs, spaced closer together means narrower armrests are optimal. But I have not heard solid corroboration on this, so YMMV ...

Now available: the High-Capacity Speedpack 915 & 915D ! Advanced Aero Storage, made in the USA.
DarkSpeedWorks.com......Reviews......Instagram......Twitter.....Facebook

"Why would you want to be the last man alive on a sinking ship?" -- Elon Musk on why Tesla Motors shares its patents with competitors.
Quote Reply
Re: Narrow vs. Wide arm position [devashish_paul] [ In reply to ]
Quote | Reply
Dev, lately I've been seeing more and more people (narrow and wide elbows), clasping their hands together. Is there any advantage to holding your hands together like that?
Quote Reply
Re: Narrow vs. Wide arm position [Louie Cayedito] [ In reply to ]
Quote | Reply
Louie Cayedito wrote:
That is helpful, thank you.


I started thinking about this while watching the 2006 Ironman Hawaii bike segment. The announcers said that Normann Stadler had a very fast position in the wind tunnel compared to the other athletes at the time. It was interesting because his position is unlike the narrow arm, high-handed position that is frequently sought after. It looks comfortable.


It seems that some other top-level professionals have bike positions that would not seem to be very aerodynamic (like Brent McMahon, below). Given that one's fastest position is highly individual (and the effects of shape is hard to predict), does it make sense to seek an aggressive but somewhat uncomfortable position? Is the efficacy of making position adjustments to improve aerodynamics purely speculation in the absence of testing?


There are many in the pro field who ride what is, in my opinion, a poor position. Some of them create enough power to overcome the advantages others may enjoy from a superior position. When it comes to performance, there are so many factors - including factors in the swim and run - that affect a race. Why is Brent McMahon in a position that is clearly less aerodynamic than others? No idea. He may have good reasons. It may be all he can tolerate. He may simply prefer it to other positions. He may have tested things and made a cost-benefit decision. He may have a terrible bike fitter. He may not listen to his bike fitter. Perhaps he's out there reading and can provide some feedback or perhaps his fitter is out there and can provide some feedback - that's the magic of Slowtwitch after all.

Your questions are difficult ones to answer correctly, because as with so many things, it depends. When you say does it make sense to seek an aggressive but somewhat uncomfortable position, the following points are relevant:
  • that assumes that being aggressive (low) means being uncomfortable. This is not necessarily the case and a great deal of nonsense is out there regarding the relationship between being aggressive and being comfortable.
  • comfort is more important for some riders than others
  • comfort and discomfort tolerance is different from rider-to-rider
  • riders can adapt to tolerate positions that might have initially been uncomfortable
  • if you can sustain a position for the duration of the event and run effectively off the bike and performance is your primary goal, then a fitter can argue that the position is comfortable enough
  • aerodynamic improvements depend on the effectiveness of the initial position - some changes are subtle, others are not

As for your second question, it is not purely speculative to analyze the aerodynamics of position changes. Changes that affect surface area in significant ways will almost always yield improvements. Changes that affect surface texture (speedsuits, shoe covers, etc.) will almost always yield improvements. Equipment changes, such moving to a Zipp NSW from a Zipp 30, can yield improvements.


Subtle changes, on the other hand (hand position, aerodrink selection, etc.) are harder to confidently assess. There will be outlier cases that will contradict best practices. Equipment selection with helmets are a good example - when someone asks whether a LG P-09 is the "fastest" helmet, we answer that in our wind tunnel testing, that was true for 5 out of 6 riders among the helmets we tested. But for one rider, it wasn't as fast as another option. Does that make it a good investment or not? Impossible to say conclusively, but it's reasonable to play the odds.


We worked with a top 10 70.3 pro in the wind tunnel in regards to computer positioning, and the best position made it difficult for the rider to see the screen. The testing didn't tell us which position was best - it simply provided us with a quantifiable benefit of that position. It is up to the rider to consider the cost of that change and whether it is a good one. If it caused the rider to have to work to see their power output and that affected head position negatively or elevated their heart rate due to additional stress, perhaps the most aerodynamic position isn't the best position after all.


If you understand aerodynamics reasonably well, you'll also know that the improvements between fit changes and equipment changes will vary depending on conditions. If you look at good wind tunnel testing with bikes, you'll notice that the aerodynamic differences between a very aerodynamic bike - say a Felt IA - and bike with inferior aerodynamics - say a Felt B14 - are different with low yaw angles than they are at greater yaw angles. If a race was windless resulting in a 0 yaw wind, the benefits of the IA will be tempered. Same is true regarding wheel choice, whether you use a disc, etc.


Not sure I answered any of your questions well, but I wanted to explain the thought processes we use in our shop to answer questions about bike fit and aerodynamics accurately.

Trent Nix
Tri Shop - Plano, Texas
http://www.trishop.com
Facebook | Twitter | Instagram | Youtube
F.I.S.T. Advanced Certified Fitter | Retul Master Certified Fitter
Quote Reply
Re: Narrow vs. Wide arm position [trentnix] [ In reply to ]
Quote | Reply
trentnix wrote:
Louie Cayedito wrote:
In team pursuit events on the track it seems that riders often adopt a wide arm position vs. narrow. How often is this aerodynamically advantageous? Or, does the event or the environment change the dynamics of the drag situations faced?
In regards to whether there is an aerodynamic advantage, the correct answer is "it depends".

For triathlon, some riders find a wider armpad position (or armpads that rotate) are essential to sustaining the aero position. A narrow position often causes shoulder fatigue and discomfort or neck/trapezius fatigue and discomfort, and consequently the rider sits up to alleviate that tension. I'm of the opinion that, for most triathlon distances, if you have to get up once to stretch your neck and shoulders, it likely offsets any benefits a narrow armpad and extension position can provide.

Additionally, if a wider position allows you a lower cockpit position (a more "aggressive" position, that is), the smaller surface area presented to the wind is typically aerodynamically superior to a narrow armpad position as well.

When evaluating aerodynamics, you've got three components to consider:
  • surface area
  • surface texture
  • surface shape

Surface area is the "eyeball" aero test. It's reasonable to think smaller surface areas are aerodynamically superior to larger surface areas. Surface texture is where smooth surfaces, speedsuits, aero helmets, shaved legs, etc. comes in. It's harder to identify what's best, but the basics are easy to analyze (e.g. shaved legs are better than unshaved legs, speedsuits are better than jerseys, aero helmets are better than basic road helmets, etc.).


Evaluating the benefits of shape, which a narrow armpad position affects, is much more complicated to analyze. CFDs and wind tunnels are essential to identifying which shapes are better than others, whether you are talking about wheel shapes, posture differences, etc.

I would have thought that something as simple as start at the top off a hill at 35-50 kph (choose your speed) and coast down the hill 5x with narrow pad vs wide pad, turtles vs un turtled and out of 20 tests see the terminal velocity for the 4x five tests and now you know which is fastest. Then see which one you can adapt to ans sustain the position and watts and make tradeoffs. I don't think the average age grouper would need to get into CFD or windtunnels because seconds don't matter as much. At the pro level sure. Coming up with a sustained position for 90 or 180k that you can stay bolted in is much more important.
Quote Reply
Re: Narrow vs. Wide arm position [devashish_paul] [ In reply to ]
Quote | Reply
devashish_paul wrote:
I would have thought that something as simple as start at the top off a hill at 35-50 kph (choose your speed) and coast down the hill 5x with narrow pad vs wide pad, turtles vs un turtled and out of 20 tests see the terminal velocity for the 4x five tests and now you know which is fastest. Then see which one you can adapt to ans sustain the position and watts and make tradeoffs. I don't think the average age grouper would need to get into CFD or windtunnels because seconds don't matter as much. At the pro level sure. Coming up with a sustained position for 90 or 180k that you can stay bolted in is much more important.
The conditions won't be exactly the same and the rider's position won't be exactly the same for any two of those tests. But sure, bigger changes will certainly be detectable, while subtle changes maybe not so much. Additionally, even testing like you mention is time consuming and will be restricted the sample of products/positions you are testing.

I hope I didn't make it seem like it's impossible to make aerodynamic improvements without a wind tunnel, because that wasn't my point at all. If that's how it read, I apologize. I'm just pointing out that there is some complexity with aerodynamics that can't be simplified into "buy this bike, these shoes, this helmet, and hold your hands like this for maximum success". Shape assessments are hard, surface area and surface texture assessments are relatively easy.

Trent Nix
Tri Shop - Plano, Texas
http://www.trishop.com
Facebook | Twitter | Instagram | Youtube
F.I.S.T. Advanced Certified Fitter | Retul Master Certified Fitter
Quote Reply
Re: Narrow vs. Wide arm position [Louie Cayedito] [ In reply to ]
Quote | Reply
Related to the topic under discussion, is there any consensus about hand position?

It seems to vary dramatically, from actually overlapping (rare) to a spectrum from very close to fairly separated. I can see the intuitive argument for a V rather than a W shape meeting airflow (in this case airflow from below relative to those letters), but conversely I have the impression a W shape with the two hands separately punching through the wind may actually facilitate better airflow around the body. I've even heard the argument that hands should be directly in front of elbows, the logic being that angling them in exposes the forearms to the air and creates more drag, though that position creates additional stresses on the shoulders and also seems rare, though you do see it occasionally.

I get that hand position is closely related to what's going on with the rest of the arms and that it's hard to generalize. But I'm still curious if folks feel comfortable making any generalizations about this issue.
Quote Reply
Re: Narrow vs. Wide arm position [trentnix] [ In reply to ]
Quote | Reply
trentnix wrote:
devashish_paul wrote:
I would have thought that something as simple as start at the top off a hill at 35-50 kph (choose your speed) and coast down the hill 5x with narrow pad vs wide pad, turtles vs un turtled and out of 20 tests see the terminal velocity for the 4x five tests and now you know which is fastest. Then see which one you can adapt to ans sustain the position and watts and make tradeoffs. I don't think the average age grouper would need to get into CFD or windtunnels because seconds don't matter as much. At the pro level sure. Coming up with a sustained position for 90 or 180k that you can stay bolted in is much more important.
The conditions won't be exactly the same and the rider's position won't be exactly the same for any two of those tests. But sure, bigger changes will certainly be detectable, while subtle changes maybe not so much. Additionally, even testing like you mention is time consuming and will be restricted the sample of products/positions you are testing.

I hope I didn't make it seem like it's impossible to make aerodynamic improvements without a wind tunnel, because that wasn't my point at all. If that's how it read, I apologize. I'm just pointing out that there is some complexity with aerodynamics that can't be simplified into "buy this bike, these shoes, this helmet, and hold your hands like this for maximum success". Shape assessments are hard, surface area and surface texture assessments are relatively easy.

HI Trent, I agree with your points. What I was getting at was trying to arrive at some "macro" baselines (if they show up in your field testing which it may or may not). This is probably sufficient for a lot of age group long course racing. Would not be sufficient for a track team pursuit team racing for Olympic gold where millisecond gains per kilometer can aggregate up to a 1/10t over 4000m at 60 kph.

One more thing on wider vs narrow.

In a one rider config the frontal vs depth "ratio" is much different than a 4 rider train where the depth is essentially 4x as deep. So if you look at X/Y where in the pursuit case Y is 4x larger, adding maybe 2-4cm of width the air/elbow interface (your X value) may be less of a penalty when looking at the overall aerodynamics of the 4 rider train WHILE being able to generate more top line power from the guy in the front pulling the train.
Quote Reply
Re: Narrow vs. Wide arm position [devashish_paul] [ In reply to ]
Quote | Reply
This thread interests me. I would be interested to see some test results between a narrow vs. wide arm position. My fitter explained that testing had indicated that a wide arm position is more aerodynamic, but I did not see the tests he was citing. Regardless I trusted him. More importantly, a wider position was more comfortable for me, which takes priority for me at this point in my triathlon journey.
Quote Reply
Re: Narrow vs. Wide arm position [TennesseeJed] [ In reply to ]
Quote | Reply
I've been considering going to a wider position myself. I recently switched bikes and my new bars, Enve, are very narrow at the inside position. Bikes feels a little more twitchy than I'm used to. But I'm not the best bike handler to begin with.
Quote Reply
Re: Narrow vs. Wide arm position [trail] [ In reply to ]
Quote | Reply
trail wrote:
Just a couple thoughts...in team pursuit you're in the draft ~75% of the time, so aero could be marginally less important relative to other factors relative to IP or TT.

...and the power output for TP is large. 600W+ in lead position. Possible that wide arms might be beneficial while generating 600+W - more leverage on the lateral motion of the bike. Just guessing. I don't know.

No, not at all. Aero is extremely important, even in the draft.


AndyF
http://alphamantis.com
#findyouraero
Quote Reply
Re: Narrow vs. Wide arm position [devashish_paul] [ In reply to ]
Quote | Reply
devashish_paul wrote:
I believe John Cobb had some data where he showed that as long as the elbow are not wider than the waist and the hands are close together to push the air around the elbows and waist, then you still get good laminar airflow. You could do field tests riding up to the top of a hill and see what terminal velocity you hit with various hand and elbow pad positions independent of power output.

Yup, totally on the money, Paul.

In commercial fits, we will take a front photo to see if the arms can be widened without penalty. This gives us some options to test on the velodrome.


AndyF
http://alphamantis.com
#findyouraero
Quote Reply
Re: Narrow vs. Wide arm position [Louie Cayedito] [ In reply to ]
Quote | Reply
Nothing is different in team pursuit: getting aero is very important.

But we usually have two options to get someone aero:
1) pinch the elbows in and "automatically" narrow the shoulders, or
2) widen the elbows and ask the rider to actively shrug

In the case of a wider elbow position, one of the added advantages is better front wheel visibility.


AndyF
http://alphamantis.com
#findyouraero
Quote Reply
Re: Narrow vs. Wide arm position [Louie Cayedito] [ In reply to ]
Quote | Reply
I have wondered whether there is an element of reducing the cda of the whole 4 rider system by having wider hands.
Quote Reply
Re: Narrow vs. Wide arm position [niccolo] [ In reply to ]
Quote | Reply
niccolo wrote:
Related to the topic under discussion, is there any consensus about hand position?

First, there is absolutely no consensus about anything. Your aerodynamics and biomechanics constitute a unique supply/demand puzzle.

Sometimes there are some things that work "most of the time" or "often". But there's not that many of those rules of thumb. Hand position is one of those things that you just have to test, because it's extremely individual.


AndyF
http://alphamantis.com
#findyouraero
Quote Reply
Re: Narrow vs. Wide arm position [devashish_paul] [ In reply to ]
Quote | Reply
devashish_paul wrote:
I would have thought that something as simple as start at the top off a hill at 35-50 kph (choose your speed) and coast down the hill 5x with narrow pad vs wide pad, turtles vs un turtled and out of 20 tests see the terminal velocity for the 4x five tests and now you know which is fastest. Then see which one you can adapt to ans sustain the position and watts and make tradeoffs. I don't think the average age grouper would need to get into CFD or windtunnels because seconds don't matter as much. At the pro level sure. Coming up with a sustained position for 90 or 180k that you can stay bolted in is much more important.

I agree that a position you can hold is always better than a position you can't hold.

But I would disagree that:
1) It's not that big a gain, and
2) Being aero is in opposition to being comfortable.

Especially age-groupers... can gain 1-2s per km in positions that feel no less comfortable. Testing needs to be done carefully and is very difficult, though not impossible, to self-administer. I don't know about the value of CFD, but wind tunnels and velodromes can usefully save a lot of time over 90kms or 180kms.

Full disclosure: the company I work for sells aero testing services.


AndyF
http://alphamantis.com
#findyouraero
Quote Reply
Re: Narrow vs. Wide arm position [AndyF] [ In reply to ]
Quote | Reply
AndyF wrote:
No, not at all. Aero is extremely important, even in the draft.


Yes, but it becomes marginally less important relative to other factors. Maybe not marginally enough that you'd want to do much at all differently, aerodynamically, but marginally nonetheless.


Edit: But it's marginal enough that, in say, a 4-man break road bikes, generally only the front guy does the uncomfortable fake TT position on road bars. For the guys in the draft the marginal gain of doing the TT position is outweighed by its discomfort. This obviously doesn't apply to team pursuit to the same degree...
Last edited by: trail: Jan 22, 16 7:55
Quote Reply
Re: Narrow vs. Wide arm position [AndyF] [ In reply to ]
Quote | Reply
Andy,

Very interested in your product. Do you have any locations in Atlanta and do you have any pricing on the aero test?
Quote Reply
Re: Narrow vs. Wide arm position [Louie Cayedito] [ In reply to ]
Quote | Reply
Take a look at this article - FWIW - it has some interesting notes on arm position

https://www.cervelo.com/...hour-on-a-cervelo-t4

If you are curious about optimum arm position, I would look at the trends of those trying for the hour record as opposed to team pursuit. Those folks are trying to squeeze every ounce of speed by optimizing equipment and position and they are spending big bucks in the wind tunnels and doing real world testing on be track to do so.
Quote Reply
Re: Narrow vs. Wide arm position [trail] [ In reply to ]
Quote | Reply
This is actually very incorrect. The ability of a rider to recover on the wheels in a team pursuit is absolutely vital. Add to that they are trying to recover more often than not at over 400 watts so that they can continue to pull their turn on the front. Anyone who has ridden a fast team pursuit will know that miss-timing the swing down the bank on to the wheel even by a little bit will put you in a hole you can't get out of for the rest of the duration of the event. Same as not quite holding a tight formation and hitting more wins than required. The team pursuit is probably one of the most technical cycling races there is, and is absolutely brutal.
Quote Reply

Prev Next