How Important is it to stay aero?
Interesting results from today's little accidental experiment..... Headed out for an hour unstructured afternoon ride, after I warmed up I figured I would do a few FTP+ intervals on a known Strava segment.... The first one I stayed aero for most of the 7min interval and the second interval I sat up thru most of the 7min... There is 2 sets of data for each lap , one was from the exact strava segment and the other is from when I hit the lap button at the same places.... I missed the exact segment with my laps but the data is similar.
Data for Safeway to Flagpole Segment vs. Garmin Data from when I hit the lap buttons at the same exact place....
Lap 1 mostly aero Interval 7:20 , 233w , 20.5mph vs Garmin 6:52 , 238w , 20.9 mph
Lap2 mostly sitting Interval 7:23 , 244w , 20.4mph vs Garmin 6:59 , 247w , 20.7mph
Depending on which comp you use Strava or Garmin , I put out 11 or 9 watts higher on lap 2 and was slower on both accounts , pretty significant... This would equate to losing 23-60 seconds per hour even while putting out higher watts.... This is something we already know but when you see it in numbers WOW....
So the real question would be what is the difference at the same watts... I'm going to repeat this again sometime next week and try to ride both comp laps at the exact same watts .... One I will ride 100% aero and the other 100% sitting.... I'll drop the target watts to make it a bit more manageable....
Here's the link to the ride if anyone wants to take a peak... The segment to compare is Safeway to Flagpole and the laps to compare are lap2 vs lap6....... http://www.strava.com/activities/226527290/overview
Comments
I love this kind of data. Looking forward to test 2! Thanks Tim.
1 -yes, most of us put out more watts in an upright position at a certain perceived effort. But, at what cost? If you ride at the same power (watts) in aero or upright postion, which way would generate more speed? I'd say always aero.
2- But even if you can make the argument that this isn't a fair comp since you are putting forth the same effort (with one way generating more power), how will this fare over a longer period of time than your 7min interval. IOW, how will that wind resistance fatigue your body over several hours?
I think the key here is what happens when you add distance. I know I generate a lot more power when not in aero at the same effort, but I don't think I can maintain that effort at a STEADY rate over time. I'm curious to see how your further comps play out. I'm looking forward to seeing the results.
@Tim, another thing to consider is how much more a larger less aero profile will impact the data. I am 5’11” and 155lbs. When I sit up, I present a much larger profile and the resistance would be even great. As to what Brad stated. I also have several road cyclist friends. Last summer one had posted a ride on Strava where he went 60 miles at just over 20 mph. A pace and distance I regularly ride. When I commented how great his speed was, his riding buddies immediately chimed in that it was a 7 man group effort to get that speed. IMO, aero is faster especially when endurance becomes a factor.
I usually claim that aero at the same watts is worth 1-2 mph compared to riding upright. i agree a better test is over the course of a 90-120 min ride rather than 7 min, as the issue usually hits home in the last third of an IM bike leg. That's probably 10 minutes over a two hour period.
@Edwin-- No doubt the bigger you are - the bigger the sail when you sit up..... Also the faster your going the more drag is being applied (why we allow ourselves to sit up at slow speeds) not sure but would guess the spread would be larger at faster speeds rather than lower speeds.... I plan to do a run comp at a slower speed as well... BTW I did that segment a 3rd time on that ride in 8:43 , 172w , 17.3mph just riding along in aero...
@Al - No way I'm gonna do a 90-120 min test but I will make a couple more runs on the exact same segment with more control .... I'll do one run at 100% FTP 230w all aero then again sitting upright... 2nd run at 170w .74 aero vs upright...
@Matt- Bored ? Not at all.... Just an observation of data... I'm going to aerocamp at the LA Velodrome on 2/8-3/1 hence the sudden interest in data .... Looking for more speed thru positioning and gear.... Still considering an Nano bar like yours...
I love the data. As a numbers dork I like to see the numbers prove out what I "feel" or "know" (a couple things I hate, at least when I am putting much reliance on it). I have been riding my roadie a bit more right now and I agree with Al and the crew that it is over time when the effects of being upright really hit home. I look forward to seeing more!
Here is a link to the Specialized Wind Tunnel Series of videos: https://www.youtube.com/embed/videoseries?list=PLcmaLnqmqDnmn_bCR0RJ-soSCDKCKR97t
Knowing that IMCoz would be windy (making aerodynamic drag and even bigger factor in the race) I spend a lot of time working on aero the last few months. The specialized videos really started me thinking about how to find free minutes on my bike. One of their videos does a good job thinking about how much time savings you can expect for changes in CdA...
After several months of "nerding out" on the subject, I switched gears and started working on practical thoughts.
- A 1% change in frontal area makes a 5-6w savings at 21 mph (can calculate that here: http://www.cyclingpowerlab.com/yaw.aspx)
- I made a video of myself on my bike (trainer) from the front, then used Gimp to cut away the background of everything except my bike and me. Calculated the surface area, then started making improvements/tweaks to reduce the frontal area.
- I have tweaked my position so that I am 100% comfortable riding in that position for hours.
- I have integrated water, one bottle behind seat and integrated storage (Shiv)... and ZERO else on my bike
- I washed and waxed my bike before the race (my airplane is always 3-4 kts faster after a fresh coat of wax)
- Zero loose clothing - IMCoz forced us to wear bib # on bike, so I folded in half and attached so that it was snug/no flapping
- On legs into the wind, I forced myself into a lower, more aero position. I listened to the wind noise in my helmet, and would tweak position until it was the quietest - Quiet = less drag
- Whenever possible I rode inside the white line so that the hedge beside the road would partly shield the wind. The wind was quieter on that side of the road.
None of these things make much difference over 10 miles. But - together - over 112 miles, I believe there is a very material difference in speed.
We know that after about 12-14 mph, drag from wind is the dominant force that has to be overcome on the bike. We also know that while the drag induced by the relative wind goes up as the square of the speed into the wind, the power we must spend to overcome wind goes up as the cube of the relative wind speed. So - riding 15 mph into a 10 mph head wind, from a power on the pedal perspective, is the same as riding ˜25 mph. Using all the tidbits above has the effect of letting you ride into a smaller wind.
At this point - I am left with optimizing frontal area - that will be one of my winter projects.
@ Rich - these are the sorts of things that really do make IM racing fun - the endless little tweaks that all add up to big changes. You seem to have intuitively discovered ( I hope) one of the key things about "Optimizing frontal area": Head position. Using the sound of wind to tell you the best position, you have probably discovered that dropping your ears down around your shoulders provides a dramatic decrease in that frontal area. I cringe when I see folks riding around the course with their heads up in the air. It is the biggest single mistake most beginning triathletes make. The second, of course, is not staying aero after about hour 4 of the IM bike leg ... that's why I emphasized how much time difference up vs down might make aver 90-120 minutes of riding @ IM pace. At 1 mph in a 6 hour bike, it's over 6 minutes.Or, if one goes the same speed with more power, its probably a LOT more time lost on the run.
Tri bikes opened up the body angle to help with fatigue, if I remember right ,but I wonder if it's enough to give a power advantage over road bikes? And then upright - would tri v road geometry make a power difference? (Is there such a thing as "too" open?)
I'm new to biking and to EN so forgive me if this topics already been killed, run over, backed up over again.
@Rich S - Thanks for giving the rest of us some ideas for geeking out the bike setup.
@Al - thanks for lending perspective, I'm sure I'm not the only newbie lurking, and I was wondering "what does this really mean" -thank you!
-I'm curious why a 90-120 minute trial would be better than looking at 7 minutes and multiplying out?
Rich, can you share the before and after profiles? I'd love to see these.
@Rich--- Yes I have seen those video's.... Most of that is over my head and confusing.... I dont wanna know why so much as to what works for me.... Kinda like I just wanna turn the key to my car and have it start I dont wanna know the how/why behind it ! Waxing your bike? Awesome! I believe the airplane numbers ! My boat is 7 mph faster in the spring with a clean hull than it is in the fall with a dirty hull! Can you say DRAG? While I dont really understand the mathematics etc behind all this geekery I do understand the theories a bit thru real life experiences.... I have over 3000 skydives and every single one of them is an experiment in aerodynamics..... Just by changing the body position in freefall I was able to change my vertical speeds from as low as 80mph to in excess of 200mph (with just the body).... And yes you go much faster when punching a smaller hole thru the air... I love your listening to the wind while riding that is great... I hope a lot of people pick up on that comment... Another good test for aerodynamics is in the pool with a Pullbuoy swimming along with toes as pointed as you can make them and then flex your feet (whoa its like throwing out a parachute).... Of course water is thicker and its more exaggerated... My last thought on your comments is that the trailing edge of every object is almost as important as the leading edge.... Think wingshape design (aero helmets)...Then think about trailing edges of you and your bike (namely anything behind the seat!
@Al.... Pretty sure you meant 1mph over 90-120 min equal 6 minutes? 1mph over 6 hrs is 20 minutes .... The FLO guys made a comment once when comparing the FLO60 front to the FLO90 front.... YES the 90 is a faster wheel but if you sit up and drink a couple times that will negate your savings of the 90 over the 60 LOL....
@Becky... Yes the test is on a tri-bike.... I dont have a lot of experience on road bikes... Most people will report a higher watts achieved with lower RPE on a road bike or in a seated position on a tri-bike... This is probably due to a more open position when seated on tri or a road bike..... When in the aero position you are actually less open.... That is why many go to shorter cranks etc to "open" up within the aero position....Those are bike fit type questions... You may want to consider a tri-bike fit if you have never had one..I've had a couple and plan to adjust further when I go to the aerocamp .... Please feel free to keep asking questions pertaining to the different bikes , fit , etc as we have a good group in this discussion...
@Dave--- yes that is a true story... BUT its a good example of why a tri-bike is faster than a road bike! NOT to mention you consistently out-split me on the IM course when we are both on tri-bikes..... When you come to Tucson this year I'll ride my new road bike!.... OH yeah I couldnt drop Coach Rich when we rode together LOL!
2nd TEST is done ... the results will be up in a while! Good stuff!
Heres the links for the DATA
http://www.strava.com/activities/227609641/overview
http://connect.garmin.com/activity/647809679
From Garmin.
all aero 2.44 miles 6:58 21.1mph 231watts
sitting up 2.44 miles 7.:23 19.9mph 233watts
results- aero penalty of 25 seconds by sitting up while putting out 2 more watts
all aero 2.44 miles 7:53 18.6mph 178watts
sitting up 2.45 miles 8:23 17.5mph 180watts
results-aero penalty of 30 seconds by sitting up while putting out 2 more watts
From STRAVA
all aero 2.5 miles 7:14 20.8mph 231 watts
sitting up 2.5 miles 7:37 19.8mph 232 watts
results- aero penalty of 23 seconds while putting out 1 extra watt
all aero 2.5miles 8:09 18.5mph 179 watts
sitting up 2.5 miles 8:39 17.4mph 180 watts
results - aero penalty of 30 seconds while putting out 1 extra watt
I think these were very controlled with similar rolling starts , I made sure to match or beat the power by just a little of the aero interval with the seated one , feel I managed to do that and pedaled very steady thru each run....the aero runs were 100% aerobars and the seated runs 100% on the hoods.....
Obviously the faster your going the higher the penalty .... At lower speeds at some point it wont make a difference at all... What is that 8mph? While its highly unlikely you'd be sitting up at either of these speeds and even more unlikely you would do so for an entire event , but if you were to sit up thru an entire IM it would make the difference between 15-22minutes at these above numbers... In an IM there is a lot more variability with hills/wind etc....The data in this little mini-test is enough to make me think every time I'm considering sitting up in a RACE!
Maybe I'll get motivated and do a couple more at much lower watts/speeds ...
@Dave - I've only played with the before photo, making some estimates as to how much area that I can reduce. I have eliminated a lot of the extras already. The photo below is where I am now. My winter project is to improve the aero without sacrificing power by causing my hip angle to close. I made the photo by putting my iPhone on a tripod, recording myself riding on the CT for a few minutes, then editing out a frame that I thought was representative of my "typical" position. The original photo had a 1m reference stick, I used Gimp to cut the background away, to count the pixels and to measure the number of pixels in 1m. Cutout isn't perfect :-). According to all that, I am at about 0.78 M^2. Next is to find out what "good" positions are for guys my size (6' 1" and 158# in this photo) and start working on improvements. A good winter project!
I really like the thought about the pool. It is all fluid dynamics. Ultimately swimming is about force to overcome drag in the water... and it is more about drag than force. One problem that I have is the sensory deprivation while swimming. There is less to hear, see and monitor to understand how you are doing. I like the idea of doing somethings intentionally awkward (like flexing your feet) in order to develop a feel for the water flow.
We all trust our power meters and heart rates - but they only apply to the force side of the equation. We need more practical tools like wind nose and feel to help us make adjustments for the drag side.
The data is already out there: coefficient of friction tells the story. F = mu * N Where F = force of friction, mu is the coefficient of friction (or how rough something is) and N is the normal force. Simply put, the wax is smoother in the air than the dried sports drink, so it creates less friction.
So to geek out the rest of the way with F=mu*N... we want F to be lowest, so we want everything to be smooth to get mu low, and the way to affect N is mostly through angles (off the cuff, here, anyone can pipe in here). Friction applies over an area, so yes, reducing frontal area is a help, too.
I'm not sure exactly what the sail rope analogy is, but I suspect you're also starting to get into laminar vs turbulant flow. Smooth is fast, so laminar is fast.
Bingo. And I'm starting to tap out on what I remember from college from my one class.
But I love applying this stuff in the real world and "playing" with it.
Totally agree with you! I can really feel, when I haven't been in a pool for a while, when I "fight" the water, going through the motions and basically muscling my way through, vs when I get a "feel" for the water. Remember, too, body comp will affect body position in the water. And head lift: The top of your head is supposed to "punch a hole" through the water for you, but every time you lift your head straight up, your body position also goes up and down - and your "frontal area" gets big.
Again, totally agree. Sometimes you need stuff calculated and measured to the nth degree, but reality needs to check in somewhere. Especially if equipment goes down, or race day conditions aren't what you've been training in. My running forum talks about "running naked" -sans Garmin - and I think it's valuable to fly "blind" on occasion.
(Edited for block quote readability.)
I think for a lot of people that's true because their FTP is higher upright than it is in their aero position.
Whether that's because of poor fitting, lack of training, or what is a separate question.
I will leave it to the exercise physiology experts to comment on which muscles are used blah blah blah and about which position therefore should lead to a better run blah blah blah. (Not saying that isn't important, but getting to my next point....)
For an IM race, unless the TT position were inherently much worse (which it is obviously not, given the experimental data), if you finish the course in the same amount of time but have used fewer watts (i.e., spent fewer joules), that just has to be a significantly good thing for the back half of the run.
@Rich: when I started swim lessons with my coach, he kept telling me to feel the water and not fight it. At the time, I had no idea what he meant. Then one day he told me to "flicker" my palm/fingers when my arm was extended during the reach/glide before the catch. For me, it really made a difference. Soon after I was able to "feel" the water on my forearms during the catch & pull. Flickering my ankles has done the same with my feet.
(Sorry, off topic of staying aero.)
@Rich: Great photo. Guess I should be working on these points now instead of after I get my FTP to a respectable level. I just got an S-Works Shiv with Dura-Ace Di-2 a few months ago. If possible, could you email a photo of your cockpit to show how you set up (and hidden) the wires in what appears to be such a clean set-up. Thanks.
@Bob - I will send you a photo... can get you a better one when it comes back from TBT. Good points on the water! If you will PM me an eMail address, will be easier to send...
Front half of the run too!
There is no doubt that working on staying aero has helped me get a little faster, yet on my 6+ hour ride, the comfort factor kicks in from time to time, and I like to move around a little. Will have to work on that, but stretching out and sitting up seems to help me keep things going. On uphills, I'm going too slow anyway for aero to make much of a difference.
Some of the things it depends on:
- are you sitting, in the drops or aero (sitting means it it happens at lower speeds)
- are riding into a wind (headwind means it happens at lower speeds)
- how bid are your on your bike (big frontal area means it happens at lower speeds)
- ...
*edited typos - sorry for that*
Right, no set answer to this question. Coach R has a podcast from July of this year on the topic of riding uphill into a headwind, or listen to the podcast of my IM CDA race. I was riding @ 6 mph up a 5% grade into a 20-22 mph headwind, and I promise you, staying aero made a difference. My watts would spike any time I sat up.
The only time there is "no wind" is when your forward speed is equal to or less than the speed of the tail wind at your back! In most other cases, staying aero will help, if only a little, except when the slope is so steep you need more power simply to keep moving forward, and that can only be obtained by sitting up.
Al - I will have to listen to those thanks. What you're saying makes perfect sense; I will definitely have to learn out to camp out and be comfortable in aero.