Advanced, Cycling, Gear, Podcast, Technology

How to shave 14 minutes off your Ironman bike split with Jon and Chris Thornham | EP#31

 June 12, 2017

By  Mikael Eriksson

How to shave 14 minutes off your Ironman bike split with Jon and Chris Thornham | EP#31

Getting the right wheels and tires can save you upwards of 14 minutes on the Ironman bike leg. And it doesn't have to cost a small fortune any longer.

Jon and Chris Thornham of FloCycling, manufacturers of exceptionally aerodynamic, yet affordable wheels, tell you how it's possible. Plus we crunch the numbers on a number of different variables affecting aerodynamics.

In this Episode you'll learn about:

  • What to consider when getting a set of wheels
  • The importance of having the right tires for aerodynamics and rolling resistance
  • How much time wheels and tires can save you when you get it right
  • Other things you should do to go faster on the bike in the order of priority and bang for buck


Listener questions​

01:39 -

From Peter, Delft, The Netherlands

Best time of day for training?

Being time crunched, is there any research on the best part of the day for the most efficient training? For example breakthrough training in the morning before/after breakfast, mid-day or evening. Most of my training is after putting the kids to bed.

  • There is a PDF document from Touch Football Australia based on research which says that for 10-12 minute aerobic exercise or aerobic capacity training there is no difference depending on what time of day this exercise is done.
  • In 2-3 minute high intensity workouts, performance may be impaired more in the morning than in the afternoon. This is also something that I practically do myself. If I have a VO2 max workout, I tend to not do it the morning. The earliest that I would do it is before lunch around 10-11am that I’ve had had a good 4-5 hours of being awake.
  • In track running, those 5000 and 10,000 meter track races are usually in the afternoon or in the evening because the performances are better at these times.
  • On muscular strength, flexibility and resistance training there is variation depending on time of day. Strength performance is less impressive is less impressive before noon than in mid afternoon and early evening.
  • Also, there is some evidence that male hormonal responses thru resistance training are strongest in the morning which is a contradictory evidence. You’re not as strong in the morning but your hormonal response is best. So, I don’t know what to make of that to be honest. But for us triathletes, we’re not really trying to optimize strength training so that doesn’t matter as much.
  • Regular endurance training is best performed at the time of day when you normally train. And performance in races in dependent on when you normally train. So you should so at least some training at the time of day when your goal races are going to be.

Out of curiosity, what do most people put in their special need bag?

  • There is a lot. If you have your own special needs bag, please do send me your tips. But the basic ones are spare tubes, CO2 for the bike, anti-blister, general cream, spare nutritionals, band-aids, aspirin, pepto tablets which are for upset stomachs.

Peter listened to the episode with Nuno Prazeres about aerodynamics and free speed on the bike and sent this great link to a Dutch site that has measured a lot of tires for rolling resistance. 

About Jon and Chris Thornham

7:55 -

  • Twins and co-founders of FloCycling​ which they started way back in 2011.
  • Both are mechanical engineers.
  • FloCycling is a company designing and manufacturing aerodynamic cycling wheels.

What differentiates FloCycling from other manufacturers?

08:38 -

  • We design the wheels on our own to make them as fast as anything that currently exists, and then import them and sell them directly to the consumer and cut out all of the mark-up.
  • So, you can buy a set of our wheels which are comparable to anything that’s on the market in the retail category but they sell for $1,150 per set. This drastically reduces the cost but you get all the speed, aerodynamics and everything else that you are looking for in the higher-end wheels.
  • We do a lot of testing which is all highly publicized. We show it, we discuss how we do everything, we’re very open about the products that we do have.​

The pricing of your wheels is very competitive. You have some great wheels for i the $400 to $500 range?

11:00 -

  • Yes. We have two options basically. Right now, we have our Aluminum + Carbon in which the front wheel is $449. And then we also have a Full Carbon Clincher which means that the whole rim is made up of carbon fiber which starts at $549.​

What should you look for in a set of wheels and how does it impact your speed?

12:09 -

  • ​The general consensus of good cycling is that a chain is only as strong as its weakest link.
  • What to look for in a wheel is a good rim, spokes, hub and bearings and that it's built well by a good builder. Then you will have a good cycling wheel.
  • What comes down after these are your specific characteristics that you’re looking for in a wheel.
    • Do you want a carbon clincher wheel?
    • Are you more concerned about weight?
    • Are aerodynamics your main concern?
    • Do you like a wide or narrow brake track?
  • Then it really comes down to cost, what type of rider or training you are doing and your personal characteristics after you get a good quality wheel.
  • For most triathletes, the number one wheel that we recommend is a 60mm front wheel and a 90mm rear wheel.
    • Note: This measurement is the depth of the rim of the wheel. It's the distance from the tire to where the spokes start towards the hub. 
  • So, the deeper the wheel is, the more aerodynamic it is which means it is faster.
  • With the increased depth comes more surface area, and when it gets windy it can be harder to control.
  • So, what we recommend for most athletes is a 60-90 (60 mm front, 90 mm rear wheel) combo. The 60mm wheel is stable in crosswinds and the 90mm in the back is a little bit more aerodynamic and it is not affected by crosswinds like the front wheel because it has a steering axis which is the handlebars.
  • This is probably the most versatile, stable and fastest wheel combination which works for most triathletes.

Key takeaway - recommended wheel type

The 60-90 combo (60 mm front, 90 mm rear wheel) works great for almost all triathletes.

How much time can you gain for different distances using the 60-90 wheel combination?

17:05 -

  • ​There’s a number of factors going into this. One important aspect is elevation.
  • For example, in Ironman Florida, let’s say we use a baseline wheel of a Mavic Open Pro which is a standard wheel that you will find on many bikes. Let's say your time over Ironman Florida was 5 hours and 10 minutes, if you were to get a Front FLO 60 and a Rear FLO 90 carbon wheel set, you would gain 5 minutes and 47 seconds over that race.
  • If we change the race and go to Ironman Hawaii this same comparison would yield a result of 6 minutes and 54 seconds. So this is course dependent and there are a number of other factors that go into this.
  • Another thing is that there is a big impact of which tire you select. A standard OEM wheel most companies ship with tires that are probably not the best for aerodynamic reasons.
  • We’ve done a very large tire study on our blog in which we went up to the A2 wind tunnel and studied 20 different tires aerodynamically. And then we also studied tires from a rolling resistance standpoint.
    • Rolling resistance means how much energy it takes to roll the tire down the road. Think of where the tire sits on the road surface, it actually squishes a bit, it deforms. As the tire moves forward, this deformation moves to a different part of the tire where there is a transfer of energy which is lost as the wheel rolls.
Flo Cycling - Tire aerodynamics and rolling resistance

From FLO Cycling - A2 Wind Tunnel Tire Study Part 2

  • We study rolling resistance to determine how many watts it takes to move the tire. Combining those two things together, you get the total amount of watts that it takes to move that wheel forward.
  • The fastest tire that we found was a Continental GP Force 24mm. The total watts for this tire is 16.49W. So let’s say you bike with the standard OEM wheel and it has a Continental Gatorskin tire on it and use that as a baseline.
  • The amount of time that you would save using the fastest tire over on an Ironman is 3 minutes and 42 seconds per tire. So that means you would basically double that, so you’re roughly 8 minutes there.
  • So if you were to improve your aerodynamics and improve your tire selection, you’re almost 8 minutes plus 6 minutes getting close to 14 minutes in time savings over an Ironman distance race.
  • Roughly 4 minutes per tire and 3 minutes per wheel.
  • If you look at the top athletes in the sport right now like Sebastian Kienle. They work on their bikes to get every single advantage that they can find. Sebastian’s tire selection is on point, his aerodynamics are good.

How to save 14 minutes over an Ironman bike leg

  • Use a good aerodynamic wheel set >> save 3 minutes per wheel
  • Use tires with minimal aerodynamic drag and rolling resistance (like Continental GP Force 24 mm) >> save 4 minutes per tire.

What is the testing process of FloCycling?

23:11 -

  • The big question that we get a lot is what is the point of the wind tunnel?​​ You go to a wind tunnel to see or verify what is actually happening.
  • The issue with wind tunnels and designing in wind tunnels is two things. Number one, it is very expensive. Wind tunnels are generally in a range of $700-900 per hour. The other thing is that it’s also very slow. So everytime you want to make a change you actually need to build a new prototype.
  • For us what we have done is we have supercomputers to help us with the design process. In order to do that, we built a computer that mounted in front of the bicycle and it collected wind, yaw angles (the angle that the wind hits you at), and relative velocity (how fast the wind is moving in comparison to you). We collect this data to understand when we should and should not include yaw angle in the results.
  • Once we have this information, we analyze the data and create a custom optimization algorithm based on that data to develop and create rim shapes that are fast for the angles that the rider actually experiences. In order to do this, we have to use supercomputers. The amount of processing time that it would take if we did this using a standard computer would be 4.5 years to actually process the data. So we use a supercomputer that has 32 processors and we use 1000 hours on that cluster to develop the wheels that are currently out on the market.
  • Once we get all those rim shapes from the computer and we actually open the molds, we go to the wind tunnel to basically verify and test with different tires to know 100% what we are creating.
  • One of the issues with a wind tunnel is that there are multiple factors and variables and things that you just specifically can’t control for. There is always something that holds a wheel in place, you don’t necessarily have it on a bike, or the rider is not included, etc.
  • What we like to do is we like to try and come up of ways to make things as realistic as possible. And one of the ways that we did this is by working with Ryan Cooper from Best Bike Split who is a mathematician and is probably one of the top three smartest people in this industry at the moment. Ryan developed an algorithm and a model that calculates in less than 3 seconds with great accuracy the optimal wattage output at each point along the way from point A to point B based on the rider’s FTP (functional threshold power) in order to optimize their time so that they would get through the course as fast as possible without burning out.
  • So we use Ryan Cooper’s model to put in the values that we obtained from the wind tunnel which is called the CDA value (coefficient of drag) that your wheel creates. The lower this value, the less drag it produces. And then he mounts them onto a number of frames that he also has CDA values for and then compares them over a number of different Ironman courses.
  • We use this data because it gives a very realistic view of what is actually happening from course to course. A lot of people would say, “Why not just go on and ride the course with two different sets of wheels and the answer to that is that the weather conditions are different each time you ride it, the rider is different. There’s a number of different factors. Ryan's model takes into account different weather conditions and creates the same weather conditions for the comparison of products. So we this model a lot in our testing and it is very accurate and gives the user a very reasonable value of what they can expect over an Ironman course.

What is a good CDA (coefficient of drag) to aim for?

30:42 -

  • ​There’s a thing that is called human powered vehicle performance sheet which comes from a textbook which uses CDA values. There’s an aerodynamic crouch position that they talk about here and they use a CDA of 0.83 for the whole rider and bike which can be considered a bit high. A 0.7 would rather be a good measure.

Action steps to improve aerodynamics in order of priority and bang for buck

32:52 -

1. Get a good bike fit​

  • If you look at the bike and rider, the biggest cause of drag is the rider.
  • Consider first your position on the bike because there may be a lot of inefficiencies with your fit.

2. Comfort

  • If you're on a fit that is super aerodynamic but you have a limited range of motion and you’re uncomfortable, then you can’t put out the wattage that you actually have to put out or can put out.
  • Don’t kill the efficiency of your engine so to say, just because you’re trying to be as aerodynamic as possible.
  • Make sure that you have a good range of motion and you’re comfortable and you can stay in the aerobars for the full duration of the race.

3. Wheels and tires

  • Definitely get a set of aero wheels that allows you to stay in that aero position. If it’s too deep of a wheel set and you have to come up out of the bars because you’re uncomfortable with the wind you’re actually going to lose more time than if you were able to stay in the bars on a shallower wheel.
  • Tire pressure, tire selection, width of the tire - all of these things are very significant in the performance of the bike itself.

4. Proper fitting clothing

  • If you have a baggy cycling jersey and shorts versus a very tight skin suit for racing, that is actually a very high cause of drag too.​

5. Other things that can be done to make improvements

  • You can look at aspects like water bottles, front brakes, different shoes, and shaving your legs.
  • The big factors are the the first three that we talked about and those are the ones that you should primarily focus on.

What about the helmet?

35:52 -

  • Helmets can save a lot of time but it needs to be so particular to the rider.
  • For example, if I use this certain helmet it could save me a ton of time. But if another person uses the same helmet, he/she can be slower than with a standard helmet.​
  • Because of body shapes, rider positions, head positions, etc., helmets are very hard to guess. So you essentially almost have to be in a wind tunnel to get the right helmet.
  • The Rudy Wingspan is like a good general helmet for a lot of riders, but again, it’s not all riders.

Tips on what would be good pieces of equipment

37:18 -

  • Make sure you get a good fit so that you are able to produce good power comfortably​ while getting it as streamlined and minimal as you can.
  • A good choice of wheel set (which doesn’t need to be FLO wheels), tires, and helmet . Example: FLO Wheels ( 🙂 ), Continental GP 4000 S II, and Rudy Wingspan.
  • Using a wheel cover at the back is very fast, essentially as fast as a disc if not the same. A great wheel cover is at Wheelbuilder who makes the AeroJacket for $99. (learn more on Episode 25: Aerodynamics mastery and free speed on the bike with Nuno Prazeres)
  • When it’s race day, clean your bike as clean as you can. Find ways to minimize stuff on your bike and streamline it, including the cables. Tuck the cables in.
  • Try a TriRig front brake as it has an aero profile.

What is your tire of choice?

41:05 -

  • We love the Continental GP 4000 S II tires.
  • It’s not technically the fastest. The Continental GP Force 24mm is the fastest tire which is also a great option. What we like about the GP 4000 S II is it’s almost a bomb proof tire, it doesn’t cut easy. It’s got great grip on wet. It’s just an all around great tire.
  • There are two sizes they make, a 23mm and a 25mm. The 25mm tire is faster than the 23mm tire when you compare and combine aerodynamics and rolling resistance.
  • However, the 25mm tire does not always fit on all frames. So before you buy them, make sure that that tire will fit in your frame and you don’t get any rubbing or issues like that. If it does, then drop down to the 23mm tire and you will have an awesome tire for training, racing and pretty much everything that you are doing.​

How much would a bike fit cost?

42:09 -

  • You could expect to pay anywhere from $150 to $400 for a good bike fit.
  • The first time I ever got a proper bike fit was from​ Retül way back when they first started. They do an excellent job because their tools allow you to transfer the fit to any other bike.
  • Slowtwitch also has the F.I.S.T system which Dan Empfield created. What we really like about what Dan says about his fit system is, yes there are averages and he gives you a range. But he says that riders will essentially choose what is best for them.
  • So when he fits somebody, he starts them at the top of the range then work them through it and asks them, “where do you feel the best?” Yes, you need a good bike fit, but if the numbers say that you should be here and you’re hip angle is too tight, you can’t breathe and just don’t feel that you can produce power, it's not good. You want to get to a point where you feel comfortable on the bike.

Rapid fire questions

44:34​ -

More information about Jon, Chris and FloCycling:

  • Website:​
  • You can buy their wheels directly from their website.
  • One important aspect of the company is that we believe in social responsibility. We have something called “Bike for a Kid” in which 1% of sales go towards purchasing bikes and helmets for less fortunate kids.
  • We also try to give back to the planet as well. We plant one tree for every wheel that is sold. The reason why we do this is because - if you look at what we do - we actually take things from the planet. All of our boxes now are made up of 100% recycled cardboard. And we are in the process of removing all plastics. Then the production of a wheel affects the carbon footprint. So we plant a tree in order to offset that carbon footprint and give back to the planet.
  • To date, we’re about to pass 2000 trees planted already. We’re about to pass 1500 bikes that we have now provided to kids.

Links and resources

  • Send feedback to host Mikael by email
  • Connect and hit me up on Twitter - my handle is @SciTriat
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Mikael Eriksson

I am a full-time triathlon coach, founder of Scientific Triathlon, and host of the top-rated podcast That Triathlon Show. I am from Finland but live in Lisbon, Portugal.

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