This episode, challenging people’s assumptions about aerodynamics in cycling
“I’d say on average most athletes should find in the region of 15 to 20 watts at their race velocity so a good benchmark will be 10 watts will save you a second per kilometer, so you’re looking at a minute to a minute and a half saving over a 25 mile time trial for most athletes.”
— Dan Bigham, aerodynamicist, pro rider and multiple national track champion
On a recent episode of the Semi Pro Cycling podcast we had Dean Phllips on the show, a Masters rider who can basically be summed up as a multiple world champion and world record holder. It was Dean’s dedication to finding the ultimate aerodynamic setup that started our journey into aero perfection.
Today though, we’re going to take this journey one step further and challenge some aero assumptions and the way things have always been done, which is why we’ve brought in some help from a self-professed aerodynamicist, pro rider and multiple national champion.
This episode will no doubt provide you with lots of useful information that you can take away and apply to your own cycling.
Damian: Yaho everybody, if you heard the recent episode on aerodynamics you’ll know that we had Dean Phillips on. He’s the masters rider who wanted to achieve aerodynamic perfection, and he’s basically done that for himself to be a multiple world champion and world record holder. Some pretty serious accomplishments and you can guess that after all the time spent thinking about his aero position, he has some sage advice that didn’t make it onto the episode.
Dean: Make sure you can stay in position going all out. You can test a faster position, shrugging shoulders. Tricky thing with testing is finding a position that you can sustain. Reality is you are going to lose power. Set position with a bike fitter, and leave to maximise power. Important to make changes that don’t make you lose power. Find ways of maintaining power by reducing aerodynamic drag and being able to hold that position in a race.
Damian: Now, what Dean’s talking about here is basically that the lowest position isn’t always the best position and this is a great example of the types of unexpected discoveries aero testing can uncover. And that’s what we’re doing today, challenging aero assumptions and the way things have always been done, which is why we’ve brought in some help from this guy…
Dan: It’s always been done this way, bla bla bla. I hate the phrase “It’s always been done this way”. It drives me mad because it’s not a reason to do anything if it’s always been done like that. You’ve got to justify it. There are a lot of people who are anti change. That’s definitely not me. I’m always pro-change, especially for the right reasons.
Damian: This is Dan Bigham, who as you can tell is passionate about testing assumptions and also agrees with Dean that slamming your stem is the top mistake people make when trying to get aero.
Dan: It’s just been old wisdom really of lowest is fastest. You look back at some positions like Chris Boardman, who was incredibly slammed and many other top riders, and I think that was back in the day before skinsuit technology allowed good control of the boundary layers, so you could actually tolerate a higher back angle and get away with it as it were.
Damian: Like Dean, Dan’s spent time testing his aero position but he also brings a unique and interesting perspective to cycling aerodynamics from his experience as a self-professed aerodynamicist with a Motorsport engineering degree and professional experience in Formula 1. Dan has worked as a performance engineer with Pace Insights, drag2zero and has recently launched Wattshop, a high performance cycling boutique.
What’s more interesting about Dan is this aero experience is also combined with being an elite cyclist. 26-year-old Dan has only been racing bikes for 4 seasons but was just selected for the Great Britain team for the upcoming track World Championships. On his way to the world championships which, mind you, he did outside of the formal GB system, he’s picked up 8 British National track titles and rides road professionally for Team Ribble Pro Cycling.
So he has some great insights as a successful aero test case and as someone who offers aero testing services. Dan is good at uncovering the unexpected areas where you could make significant aero gains and a lot of these challenge conventional aero wisdom. Things like, clinchers being faster than tubulars, or the impact of not wearing socks…
Dan: Your leg is a cylinder and cylinders are inherently bad aerodynamically, so if you can create turbulent flow, again, you can reduce the form drag around your leg, but in simple terms there’s a big low pressure weight behind your leg, and if you can influence how the air flows around your leg even on a minute scale right close to your skin you can create some pretty big benefits in the region of sort of 5 to 10 watts at time trial velocity, which is between 45 to 55Kmh, which is obviously a good old saving for a pair of socks.
Damian: In other words, proper socks are better than no socks. Interesting hey, but we’re getting a little ahead of ourselves here, we need to know where to start before changing or buying anything. Semi-Pro Cycling producer Ciarán was the one that talked to Dan and will take it from here.
Ciarán: When I started talking to Dan it was clear right from the word go that he’s thought about aero a lot and has probably seen loads of mistakes. So I asked Dan about the biggest mistakes he sees people making. Like Damien mentioned at the beginning, Dan stresses that the number one mistake he sees is people trying to get as low as possible, and..
Dan: Beyond that, saddle height and saddle position can be drastically wrong on a lot of athletes, and if anything it’s not so much in aerodynamics here, but biomechanically it can be quite poor and that limits what you can do elsewhere on the bike if pedalling technique is bad or unstable in the saddle.
Ciarán: So it’s all about getting the fundamentals right before you can even start testing your assumptions. Now, I’m going to repeat something that you’ve heard a hundred times before – it starts with a bike fit. In the case of aero testing it’s the base of all the work you will do in making position changes. A qualified bike fitter, who has intimate experience with aero positioning, can adjust you to a position that is comfortable, powerful, and aerodynamic, and you need this baseline or it’s easy to get lost in the numbers. While trying to make a position more aerodynamic, you can do more harm than good by adjusting fundamental saddle and aerobar positioning variables. Field testing should only be used for minor changes in position and equipment; only items that do not affect the sustainability or efficiency of your position should be tested.
Dan: So yeah, I wouldn’t ignore a professional by any means. You should definitely go down that route whenever you get a new bike. What is very commonplace at the elite level in cycling, that at the start the year you get your new team bike. You take it to a bike fitter, because things change at the end of the day. Your body becomes more or less flexible, injuries come and go, you’ve got to make sure you’re all set up for the year to come. You’ve got a new bike so take that opportunity.
Ciarán: Would you do a bike fit every once once a year, maybe?
Dan: Yeah, I definitely would, yeah. People do it even more common than that. Obviously it depends how well you ‘re training is going. Is your body changing a lot? So yeah, there’s every reason to keep on top of it because it all changes quite quickly.
Damian: I want to bust in here for a moment with a word of warning. I coach an athlete that is currently transitioning from road time trials to the pursuit on the track and in his first outing on the track with his new bike he ended up being in a more extreme position compared to his time trial set-up. Of course this was unplanned – because the parts didn’t all get in on time, but he ended up doing some serious damage and while it’s not exactly clear why but basically he lost 50% of power in his left arm and experienced excruciating pain for weeks.
In this case it could of been from jumping into the extreme position and experiencing nerve root compression at C6 or something unrelated (which he is not totally convinced of). Either way, though, my warning is to take care with position changes. Most people take 12 months to fully recover from incidents like this. Luckily, this athlete has escaped that. But please please please take position changes seriously. Especially if you are a masters athlete. Now, back to the episode.
Ciarán: So once you’re all set up on your bike – then you can start testing. It’s no good having all the gear and no idea. Testing is now a real option if you want to make aero gains. It’s become more popular…
Dan: …as people realize the importance of Aerodynamics and probably really started about four or five years ago with Simon Smart and Matt Bottrill who obviously took the time trial scene by storm and people, oh and Mark Hutchinson as well really… Both of them were well ahead of the curve as it were with aerodynamics and people have now obviously realized the importance seeing huge gains for it and once one person finds a couple of minutes, within a few months, then suddenly everyone’s on to the game. So yeah, it’s not so much an advantage now but playing catch-up. So yeah, it’s getting incredibly popular.
There’s a lot of companies who are performing aerodynamic testing. It’s becoming very very popular in Velodromes around the country, probably half full with people on time trial bikes riding around rather than track bikes. They’re good facilities for aerodynamic testing so if it supports them then great.
Ciarán: In order to make the correct decisions on position and equipment you need to measure it. Aero testing has become, as Dan says, not so much of an advantage nowadays but playing catch up.
It’s a process where real-time Coefficient of Drag Area (CdA) data is used to optimise your cycling position, equipment, clothing, riding style, or combinations of all three to increase your speed. Because you are actually riding and producing the power output that you produce during racing, changes can be made that are meaningful and valid for actual riding.
A first time aero test may set you back approximately around £700 GBP ($1000 USD) or more and a repeat test might cost half that. Like Dan said, more and more Aero Coaching Services are starting to pop and a good option is learning about where you personally can make gains, but what type of gains can you expect?
Dan: It varies on person-to-person and what your sort of goals and targets are, but I’d say on average most athletes should find in the region of 15 to 20 watts at their race velocity so a good benchmark will be 10 watts will save you a second per kilometer, so you’re looking at a minute to a minute and a half saving over a 25 mile time trial for most athletes. Some can find a whole lot more. Some can find noticeably less. It obviously depends on the level they’re coming at and the level they are competing at.
Ciarán: And a word of warning here, there is a chance you may not make any gains, especially when it comes to putting your body in a new more aero position.
Dan: The human body’s quite weird in that you may look at it and say well, “I think if we move it in this this and this way then we should improve aerodynamics or if we try this helmet it should fit better”, but quite often people have imbalances, tightness, etc, that limits what their body can do and will stay in. A common one is my teammate Tipper who, we quite often bring up the story where I think we’ve done three or four aero tests on him now and found the grand total of about 6 watts, which is incredibly annoying. He’s my housemate, my teammate and I can’t find much for him.
He’s just one of those guys that has somehow ended up in what I’d say as an aerodynamically optimal position. No matter what we do, his body doesn’t want more from change and try something different, so it’s kind of sit where he is.
Ciarán: So once your baseline position is set up, it’s time to start testing, whether that’s with an aero coach or on your own. But where do you start? I asked Dan about where he starts with his clients. Something even he struggles with.
Dan: It’s a tough one really and there’s a lot of chicken before egg scenarios of where do you go? when I’m aero testing clients I often wonder do I start… Do you go through a range of helmets, find the fastest helmets for you and develop around that helmet, or do you find your fastest position and hope that you then find the best helmet to suit that position, but most gains on the whole are around front-end optimization so stack height, pad width, hand height and helmet, that’s where I’d say probably 60-70 percent of your gains, maybe eighty percent can come from.
Equipment on its whole, yeah you can find a huge amount in wheels and frames Etc, but that’s purely down to the big spenders, but you can get probably eighty – ninety percent of the way there just by focusing on your positioning your clothing and your helmet. If you have to break it down, let’s say a total amount of aerodynamic drag we are talking 20 to 25 percent is your bike and your equipment and around 75 – 80% is the rider and how they position themselves so yeah, it’s purely really to focus on that and get the rider in a good aerodynamic, but also biomechanically efficient and comfortable position especially for longer time trials when you’re doing fifties, hundreds maybe even 12 hours it can be a big factor in how well you hold that position and the stability of that in your overall performance.
Ciarán: There was something in there that I want to stress by saying again – making aero gains is not just spending big on frames and wheels, like Dan says…
Dan: there’s a lot of things that I would put a lot of good money on being faster with riders when you’re testing them, and they just turn out that they’re not.
Ciarán: Instead, put your initial time into what I’m gonna call the golden triangle of aero positioning, clothing and helmet. By focusing on these three you can get 60-80% of the way there. And when Dan talks about position, he is referring to front-end optimization so stack height, pad width, hand height and helmet. Even changes such as hand position can be included in this list, for example thumbs forward. I actually found a study from 2010 called Optimal hand position for individual pursuit athletes. It tested the aero drag of four hand positions on aero bars. Hopefully you can picture them – they are:
- Normal hand position – this is the thumbs forward position
- Thumbs inside – rotating the hands in from the normal hand position
- Fist grip – holding the end of the aero bar ends with no gaps in the fingers
- Arrow grip – forming an arrow at the end of the bar by touching index and middles fingers.
The results? – Aerodynamic drag can be reduced significantly by adopting an arrow style hand position when riding with aerobars.
But all of this is down to testing and along with position gains there are gains to be made from your equipment choices. But remember Dan says you can get 60-80% of the way there by focusing on positioning, clothing and helmet.
Here’s Dan’s final word on positioning…
Dan: On the whole I think…. trial and error and see what works really.
Positioning aside, let’s have a look at clothing – namely what Dan knows about skinsuits.
Dan: It’s a hard one, and I did a test recently for cycling weekly where we brought in 6 or 7 skin suits. We had three test riders. We tested at 40, 45, 50, and 55Kmh, and the big take-home was skinsuits are incredibly personal to the rider, so there’s not really a rhyme or reason for picking one over the other beyond testing it for yourself.
I mean a lot of the top skin suits nowadays are developed for roughly 45 to 50Kmh. Bioracer are getting quite good at developing skin suits that suit certain shapes of riders at certain velocities, but I think it’s looking at more at the top brands, but then there are there are other brands like Velotech that we run who’ve done in the grand scheme of things relative to some of the top brands minimal aero testing and development but have ended up with a very fast suit, probably somewhat by luck, but there’s a lot in the design and use of certain materials in certain areas for example neoprom where you’re using texture or trip lines or different surface roughness to reduce what’s called turbulence which can in certain areas at least reduce your aerodynamic drag. But to say this suits faster than that suit is kind of ignoring a lot of the factors of how aerodynamic drag is produced on a rider, so it’s it’s hard to be clear on that.
Ciarán: I mean even in road races you’re seeing skinsuits rather than the bibs and top set up.
Dan: At the end of the day you’re out there for three four five six hours in road races and if you can ride around even in the peloton and saving five watts, ten Watts, that’s a whole lot of energy that accumulates, so you’re noticeably fresher by the end of the race, and that’s at the end of the day that’s where races are won and lost really aren’t they? At the back end. Yeah, you can save a huge amount if you’re in the break, and let’s say you’re with three other guys taking turns at 45k an hour for four hours, then it’s a long old time trial really isn’t it. You’d be silly to be chucking away 5 10 15 20 watts.
Ciarán: So skinsuits have the potential but there are no clear winners. It just a matter a testing them out yourself, and I’m going to say the same about helmets, you can find out what Dan uses at the end of the show, but really, like Dan says, you just have to go through a range of helmets to find the one that works for you and your position.
Now we can move out of the golden triangle of aero and into other equipment choices. This is kinda the fun stuff because any tests results aren’t so personal and there are products that are clear winners. One of the more surprising ones is tires. This is definitely one that goes against the “It’s always been done this way” school of thought. Tubulars or tubs or glue ons have been the tire choice, especially for track racing, for as long as they have been around but Dan has run the tests and found conclusively that clinchers are faster and he knows which ones as well.
Dan: Yeah, so if you look at it from a tire aerodynamics viewpoint a clincher and a tubular behave very very similarly. People think that “Oh a tubular can go up to 150 – 200 PSI”, and therefore you should run it at that level, which is definitely not correct. Tire resistance you can break down into two sort of factors of what’s called hysteresis losses, which in simple terms is the energy required to deflect the tire when it goes to the contact patch of the bottom.
It’s a bit more confusing that and then when you get to sort of higher pressures, or higher velocities, or rougher surfaces you get what’s called suspension losses. I think someone’s termed it tire impedance, which is a bit misleading, but effectively your tire starts bouncing. So at higher pressures you effectively can lose out all those benefits you gain from the smooth surface and quite often a significant amount more.
The good thing with clinchers nowadays is there’s a whole lot more development going into them, especially with tubeless clinchers. You’re not running an inner tube. You reduce the amount of material in the tire, so you reduce the hysteresis losses, and they roll faster because of that. So if you look at a lot of the tire data out there for the Corsa Speed G plus, whatever designation it is now from Victoria which has proven to be the fastest tire out there.
You look at their tubular version and their clincher version and the clincher is a whole good way quicker, you’re talking a good handful of watts per tire, which is obviously huge. I think there are multiple advantages to that as well. With a tubeless clincher you’ve got sealant in there, so if you do ever catch a little nick then nine times out of ten you’re probably going to seal it so puncture protection’s up. Clinchers are easier to change just yeah, multiple advantages really.
Ciarán: A cycling product that lives up to its marketing claim! Because Vittoria does actually claim that the Corsa Speed tires are the world’s fastest tire. The other product Dan mentions is Rule 28 socks which unbelievably, as Dan said at the start of the episode have in the region of a 5 to 10 watts saving! A pair will set you back around 30 quid… Not cheap for socks but definitely worth the gains.
Before we finish off with equipment what does other aspects of cycling and aerodynamics does Dan think we we’ll see in the future?
Dan: I think we’ll definitely see more integration and more different designs like the 3T Strada bike for example. You’ve probably seen that where they’ve gone single ring, no front mech, disc brakes, etc. They’re pushing what is conventional really. I think that’s going to become more commonplace. I don’t think we’re going to see any standout wild designs were someone’s going to come up with something crazy and funky. It’s just the UCI have put a bit of a stranglehold should we say on the regulations that you are working in quite a tight window, so I think we’ll just see people taking those more innovative solutions and bringing them all together and making what’s quite a unique bike like the 3T.
Ciarán: Stick around until the end of the show if you’re interested in exactly what Dan’s pursuit set-up is. Dan final bit of advice is a little sneaky but may be the last piece of your aero puzzle.
Dan: There is a lot to be said for that in having a look at what the top guys are doing, but equally it is very personal, so yeah look at what they do with their hand position, elbow position, helmet, skinsuit, wheels, tires, etc At the end of the day they’re going fast for a reason which can get you pretty damn close if you look about, do bit of research on your equipment, and what you’re trying to achieve, but at the end of the day these professionals are in business for a reason because they’ve got the experience and they can fast-track you to that fast position or having the right equipment, so you obviously pay for the service, but it can save your other time effort and money to get you there quickly.
Damian: I’m going finish off here at the end to recap the important takeaways from Dan’s interview that I learnt:
- The importance of a good bike fit prior to aero testing.
- Up to 25 watts to be gained from aerodynamic testing.
- Most gains are found in front-end optimization. Stack height, pad width, hand height and helmet are where up to eighty percent of gains can be found. Position, clothes and helmet are where it’s at.
- You might not be able to change your body into a more aero position.
- Optimising skinsuits, socks, clinchers over tubulars can bring big gains.
- That without spending a lot of money try to emulate as much as comfortably possible from the pros.
Damian: It’s time for the Radar. The segment of the show where I talk about something that has popped up on my radar – whether it’s a product, study or performance tip…And today, I’m going to squeeze the last bit of aero into the show with a short round-up of the DIY aero testing options out there.
If you’re a die-hard DIYer then you’re best investing your time into some for of Aero Online Software. That will give you the foundation to run your own aero tests. There’s basically only a couple of options at the moment.
- The original and probably still the best is Golden Cheetah’s Aerolab.
For starters it’s free – it’s the program that Dean Phillips uses. It’s an ugly user interface but it still gives you everything you need to get the job done.
Fast Aero Lab provides an easy-to-use analysis engine. It’s a little more user friendly than Golden Cheetah’s Aerolab with a similar outcome. Plus it’s also free and you can get some help if needed.
Is a math and physics engine takes your power data, course info, and race day conditions to predict your race performance and create the perfect power plan so you can hit your best time. This is still fiddly but the user interface is the best out of the 3 options – but of course you have to pay to use it.
- Aeroweenie – Android Only
Full frontal area is an Android application that can run on any Android device, version 3.0 or higher, with a camera, to measure the frontal area of things. It gives you an estimate of you frontal area so you can make changes and see what impact that has on your aerodynamics. A cool little app but not as powerful or useful as the other options.
And that’s it – pretty slim pickings. I have a feeling that the real-time products that will be out soon will blow these software products away and be the go-to in aero. I’d like to say that by the end of the year this will be the case but I think it will take longer than that – maybe mid-way through next year until we start to see real life implementation of these products.
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Alright, well, I’ll be back in 2 weeks. Thank for listening
Dan: So my track bike is a Cervélo T4. There were a lot of other bikes that we were looking at as teams, but unfortunately we don’t have a frame sponsor and trackbacks are quite hard to come by in the right size at the right price. So we went down that route and they are good frames. Wheels wise we’ve worked a lot with Walker Brothers with the wheels and developed some really good aerodynamic wheels with those. They’re really open to just trying different ideas, and he’s a mad time triallist from back in the eighties and nineties and if anything they’re the best type of people for development. Then at the front end we’re running USC aero bars the R1 aero bars and stem, a super clean set up for the T4, and I don’t think anybody should ever pick anything else on that bike in all honesty so that’s pretty good. Other than that there isn’t anything that really stands out. We’re with Victoria pista speed tires. We’re on PEEKrings, a company called Pyramid Cycle Design, the only company in the world that make them. They’re a special type of carbon fiber composite that are really really good for reducing the drivetrain resistance so again, that’s a cool little thing that we’re doing that a lot of the other teams aren’t and then everything else is reasonably standard off-the-shelf, so yeah, Rule 28 socks, Velotech skinsuits, Giro shoes and helmet.
Hosted by Damian Ruse
Produced by Ciarán Mac Parland
Sound Engineer: Satyr Productions