Simon Smart has been recognised as one of the most influential people in the bike industry, being responsible for the design of a number of record breaking products as well as helping some of the highest performing pro athletes go faster. 

He and Andy go back a few years and so when they bumped into each other at the Cycle Show in Birmingham recently, we jumped at the chance to ask the King of Aero a few questions to help you realise some performance gains by optimising your positioning and bike setup...

So, Simon, talk us through your background in aerodynamics in sport?

Well, my background is in motorsport and I've always held a real interest in making things go faster.

I have worked for a few F1 teams, and whilst working as a race engineer at the track I became fascinated with aerodynamics. This led me to join the Jaguar Aero department in 2000 where I worked as an Aerodynamicist until 2007.

That was actually when I first met Andy, who was training Mark Webber at the time. During his visits we got talking about cycling and he then went on to coach me in road cycling – that was in the days when I had time to do a bit of training!

It was a fun era to be in F1. We even had a Jaguar mountain bike team and raced with Andy, his brother Dave and Mark Webber at Eastnor Castle 24 hour MTB race. Not sure they would allow an F1 driver to do that on his weekend off these days!

I remember coming back from a night stint with really bad cramp and Andy chucking a bag of Salt & Vinegar crisps at me and saying that the product I was using didn’t have enough salt. He was right and crisps are still my go to treat after a long ride, although I'm sure Andy would probably recommend something healthier like PH 1500 these days of course...

Should people look at their position or their kit/equipment first when trying to be more aero?

As a rule of thumb, for an average-sized, unoptimized male athlete, 85% of drag can come from the body. With position optimization, the body/equipment ratio can come down to around 70%, and for smaller female athletes it can be 60%.

So there's a point where there are diminishing returns in body position and then investment in equipment is necessary. But with these numbers you can see why you should always start with the position...

Interesting. Ok, how do you balance being more ‘aero' with comfort and power output?

Your best performances are achieved with your optimal power/drag ratio.

So it’s not about producing the most power or being the most aero, it’s about finding the best compromise. It’s what we at Drag2Zero refer to as the “aero sweet spot”.

In triathlon it also involves consideration for running off the bike. Finding that right position is no easy task and it's unique for everyone. In wind tunnel and studio aero fit sessions we try out a lot of positions - some for improving aero, some for power. We then piece the information together and come up with a plan so that the athlete can adapt and find the sweet spot.

Due to the adaptation phase, a lot of decisions on the day come down to experience. That’s why I would always recommend that you work with experienced fitters. A wind tunnel is just a tool, invest in the people running the session.

Over the last few years we've also started pre-tunnel sessions where we evaluate biomechanical performance and this then defines an envelope we can work in for aero adjustments. We use Retul for this, again it’s a really good and reliable tool – but a tool all the same - and the decisions we make maybe are certainly different from a conventional bike fitter.

Who’s the one athlete that you feel you’ve made the biggest gains with?

The time splits and aero gains are certainly smaller these days, as most pro riders already have decent baseline positions. So I'll have to go back a few years for the biggest gains...

My most satisfying fit was Tony Martin. At the time he trailed Cancellara by 2 mins in a typical TT. We got him a position that I thought was unsustainable, but said "if you can hold that, you would beat Cancellara". And he did very soon afterwards, and that was simply down to Tony’s belief and determination. Full credit to him, many riders could do that in the tunnel, but not on the road.

That’s what is great about cycling, being aero is a skill in it's self and people like Wiggins, Dowsett, DuMoulin have that same mind set.

There are many amateur riders who have believed in the science and embraced aero performance in the same way, they appreciate that a visit to the wind tunnel is not a magic bullet but that time is needed for adaptation and they stick with it. Seeing these transformations is one of the most satisfying parts of my job.

I'll bet. On that note, what’s the product that you’re most proud of developing over the years?

Tricky one! I'm proud of all the products I've developed like the Giant Trinity, Scott Plasma 3, 4 and 5, Scott Foil, ENVE SES wheel range, Endura D2Z clothing, D2Z disc wheel, D2Z components. Many of them have gone on to break records both in racing and in the sales books!

My first design project in this industry was the Giant Trinity, which was made possible with the help of Lars Teutenberg and Andy Wolny. It was all very last minute, made under the radar. They made 6 prototypes and in one weekend won 6 UCI national titles. I even got a call from the Giant boss. You don’t get many projects like that in a lifetime and that project will always be special to me. The design was iconic and was one of the first bikes with an integrated front end which is now of course the norm.

Commercially I would have to say that I'm most proud of the Smart ENVE System wheel range. When I started working with ENVE in 2009 we were one of many small wheel brands, to think that almost 10 years on we would take second place in the Kona wheel count as we have for the past few years, was almost unimaginable.

That's awesome! Ok, so what’s the best value for money aero upgrade the average Joe could make today? What are the best watt savings per £/$ that an athlete can achieve?

For an "average Joe", it has to be our Aero fits. For £350 you get 10 years of my wind tunnel knowledge combined with Retul to get you into the aero sweetspot.

You spend three hours with two of our excellent technicians and they have an arsenal of tools to make the bike fit you (which sounds obvious but is actually a rarity).

One challenge for customers has always been building the bike up afterwards. After 10 years I'm glad to say that we can now fully support any bike build with bespoke parts and a mechanic service.

We hear about how a chain can save X watts and a helmet can save Y watts of power expended. How does that translate in to reality? For example, say someone has a target output of 250 watts for a 40km TT, how would a combined saving of, say, 30 watts from mechanical/aero changes actually work on the day?

This sounds like a simple question, but often leads to confusion and it's not that straight forward to answer. Everyone likes to quote watts, but when it comes to aero gains it can be misleading if the numbers are not corrected for the appropriate speed that the rider is achieving.

Mechanical and aero gains can be added together, but the ratio of X/Y will change throughout the speed range. A chain will reduce losses, and you can assume that this is a constant % saving of the total power output (there will be some change in efficiency depending on the level of power, but for the purposes of this question we can assume its constant).

Let’s say a new chain saves 2% (for the purpose of this explanation), that’s 5 watts (for our 250 watt rider) more at the wheel throughout the ride regardless of speed.

The helmet is different. If the rider found it was a massive 20 watts faster at 50 KPH in a wind tunnel, at 40 KPH it would only translate to a 10 watts saving, and at 20 KPH, its only 1watt.

This demonstrates that, if you're riding on a gradient at 20 KPH at 250 watts, then you'll feel the 5 watt gain from the chain but would not feel any benefit from the helmet. Conversely, on a 50 KPH straight at 250 watts, you would still benefit from the chain but the effect of the helmet would be far more noticeable. That’s why people always notice aero gains at high speed, and mechanical gains at low speeds.

So, to make these numbers real let’s use the example of a 75kg age group triathlete with a road helmet and standard chain who produces 250 watts on a flat 40 km TT.

His race time is 59 mins, 55 secs. He repeats the course with the aero helmet that he had tested in the wind tunnel and his race time reduces to 59 mins 2 secs. At the next race he fits a super efficient chain and rear mech, which improves the drivetrain efficiency by a massive 2%. This brings his race time down to 58 mins and 35 secs.

Interesting stuff! Is it worth spending the time and effort on aero changes on the bike for a Standard distance triathlon, or would the time be better spent working on running and swimming?

Definitely - let me give you an example using one of my clients...

Our age group 75kg triathlete, pushes out a respectable 250 watts on the bike without compromising his run times. He has put a lot of time into run training and his run times are now only improving by a few seconds - it’s diminishing returns.

He could push harder on the bike, but has tried that and it was a disaster as he gained 2 mins on the bike and lost 4 mins on the run. He rides a TT, his position looks okay, but it's not optimised. At this level it would be viable to reduce total aerodynamic drag by 15% through clothing , helmet and position.

With all the challenges of balancing work, family and training he finds that just sustaining his running form and power output year on year is an accomplishment in itself. The session at the wind tunnel brings his CDA down from 0.2400 to 0.2100 without affecting power output. Next season he is 2 mins 30 secs quicker on the bike for the same power output.

It’s a game changer at Olympic distance, and results in him winning his age group!

The key to all of this is that it's possible to gain on the bike through aero without sacrificing your performance in the swim and run. We have always been very conscious that advising triathletes is very different to advising pure time triallists.

You do need guidance from an experienced expert. It might look easy, but it takes experience to optimise a rider position without it impacting the power output and compromising the run performance.

We're sold! What’s the effect of tires and rolling resistance on a 70.3 or Ironman bike segment?

Let’s assume that our 75kg rider has an A race and wants to trade his old faithful train/race tires with butyl inner tubes for a lightweight TT tire with latex tubes.

This reduces rolling resistance by 25% and gives a watt saving of around 14 watts and almost 3 min in time - just don’t get a puncture! 

Do aerodynamic changes have any impact for climbing above a 5% gradient, or is it all overcoming gravity at that point?

Going back to average 75kg Joe. On the flat he travels at 40 KPH at 250 watts. When he gets to a 5% gradient the speed will drop below 20 KPH and the majority of the power will be used to overcome gravity.

The aerodynamic drag would be less than 20 watts and therefore aerodynamics setup will have a negligible effect on his performance.

What’s your take on the multiple aero sensors that are coming to market? Do you think everyone will have one in a few years time in the same way most of us have power meters these days?

As we have identified in the above questions, aerodynamics can be incredibly important to a cyclist’s performance. So, naturally riders want to know how aerodynamic they are and, rather than going to the wind tunnel or track, it's possible to estimate CDA (Drag Coefficient x Area) from a Garmin file that contains speed, elevation and power data. The main limitation to this is that the wind conditions can make a big difference to the results.

The aero sensors are anomometers that can measure the true wind speed rather than the speed you're travelling at and some sensors can also measure wind angle.

We developed our own sensor several years ago and this has proven very useful to assist in field testing. But they can be expensive to manufacture, calibrate and difficult to use.

Several manufacturers have now developed anemometers that are affordable and easy to use. This is clearly a game changer as potentially riders will be able to develop their aerodynamics in the field rather than relying on costly wind tunnels or track sessions.

I think the outcome of this will really depend on the accuracy of the sensors. Many amateur riders are already very aerodynamically optimised and looking for lots of small incremental gains which will require a high level of fidelity.

These sensors will give us a better idea of the conditions that we ride in and possibly remove a level of noise from our power data, but they are still just a tool and could lead to further confusion.

It'll be fascinating to see how it changes the aero market, but when athletes are chasing refinements of 1% I suspect they still need to test in a controlled environment. F1 cars have an incredible array of sensors for testing at the race track, but they still need wind tunnels.

What do you think will be the next big breakthrough in cycling from a technological standpoint?

In the 10 years of running Drag2Zero, we have seen cycling performance improve significantly.

Riders have a better understanding of coaching and nutrition, and my impression is that people have longer to train. But with all other life pressures and physiological limitations, I'm not sure that the average power output has gone up by very much, maybe 5%.

But, on the equipment side, tire manufacturers are reporting a 40% improvement in rolling resistance and, in the wind tunnel, the average drag of a rider must be at the very least 20% lower.

So, if you stand back and look at the basic physics of a cyclist, we really have come a very long way in weight, stiffness, rolling resistance, drivetrain and aerodynamics. We will continue to develop products and shave off 5 or 10 % off (not very much), but ultimately the next break through is developing tools that ensure that the amateur athlete is optimised to their full potential.

Great stuff, thanks Simon!

Learn more about Simon and Drag2Zero's work at and get more insight into how the pros get more aero.