January 28, 2014

FLO Cycling - The Great Debate - Aero vs. Weight *Edited

What will save you more time?  Improving the aerodynamics, or decreasing the weight of your wheel set?  Jon and I have probably been asked this question hundreds if not thousands of times since starting FLO.  When designing FLO wheels we focussed primarily on aerodynamics.  We did that because in almost every situation possible, aerodynamics have a far greater impact on time saved than weight.  However, I don't just want to claim that.  In true FLO Cycling fashion, I want to do my best to prove that fact.  To do that, I asked a VERY smart friend to help me out.  

Help from a Friend
Ryan Cooper is an math Ph. D.  He does the kind of math that makes even engineering math look easy.  His area of study focuses on optimization mathematics and he has used that skill to develop a very cool web application called "Best Bike Split".  Best Bike Split has the ability to take in a ton of data like the rider's FTP, weight, their bike set up including wheels, tires and position, and then predict a bike split for a particular course.  This software is surprisingly accurate.  I've seen Ryan predict IM and HIM bikes splits within a minute several times.  He's right almost all of the time.  If you'd like to learn more about Best Bike Split, be sure to check out our Interview with Ryan where he details how the software works.  

The Study
The goal was to determine what saves you more time when selecting your cycling wheels, aerodynamics, or weight.  To do that, Ryan and I created a list of potential race day wheel set ups.  The wheel set ups ranged from lightweight and non-aero, to not lightweight and very aero.  

We then ran a virtual rider through some of the most popular Ironman courses and some "extreme" courses using each of the wheel set ups.  When all of the test runs were completed, we compared the times.

The Ironman Courses
The first three courses that we selected where some of the better known Ironman Courses.  We selected a course that was flat, one that had rolling hills, and one that had a long steady climb.  Weight becomes more important on hilly courses so we wanted to include hilly courses to give weight the biggest advantage possible.  Here are the Ironman Courses we selected.  

The Flat Course - Ironman Florida
Distance: 112 miles
Total Gain: 991 feet

The Rolling Course - Ironman Coeur d'Alene
Distance: 112 miles
Total Gain: 4804 feet

The Long Climb Course - Ironman Lake Placid
Distance: 112 miles
Total Gain: 4612 feet

The Extreme Courses
Because we so firmly believe that aerodynamics are more important, we also selected two courses known for being some of the hilliest courses you will find.  Here they are.  

SavageMan 70
Distance: 55.7 miles
Total Gain: 6717 feet

Alpe d'Huez
Distance: 8.2 miles
Total Gain: 3514 feet
Average Grade: 8.1%

The Wheel Sets

The Aero Wheels
FLO 30/30: 1624 grams
FLO 60/90: 2074 grams
FLO 90/DISC: 2259 grams

The "Un-Aero" Wheels
We created 2 hypothetical non-aero wheel sets that varied only in weight.  The aerodynamic properties given to this wheel were that of a common training wheel like a Mavic Open Pro.  

Light Training Wheel: 1100 grams
Heavy Training Wheel: 2259 grams

The Rider
We simulated a rider that we felt resembled a good majority of male age group athletes.  This allowed us to keep things realistic and useful for our largest group of readers.  Here is the athlete profile.  

Rider Weight - 170lbs
Rider FTP - 250 watts
Bike 1 - Cervelo P2
Bike 2 - Cervelo S5 (used only on the Alpe d'Huez simulation)

We will assume that this rider will ride all of the courses at 75% of his FTP with the exception of the Alpe d'Huez.  On the Alpe d'Huez the rider will exert a 100% FTP effort.

The Results

The Ironman Courses
A baseline time has been set for each Ironman course below.  The time for the "Heavy" Training wheel to complete the course was used as the baseline time.  We then compared all other wheel sets to the baseline, to see whether improving aerodynamics or decreasing weight had a bigger influence on the time saved.   

Ironman Florida
Ironman Florida Bike Course Elevation
Baseline Time
Training Wheel (Heavy Version 2259 grams) : Time on Course : 5 hr 21 min 44 sec

Time Saved by Improving Only Weight
Training Wheel (Light Version 1100 grams) : Time on Course : 5 hr 21 min 42 sec
Time Saved = 2 sec

Time Saved by Improving Only Aerodynamics
FLO 90/DISC (2259 grams): Time on Course : 5 hr 12 min 55 sec
Time Saved = 529 sec = 8 min 49 sec

Other FLO Wheels

FLO 30/30 (1624 grams) : Time on Course : 5 hr 15 min 28 sec
Time Saved = 376 sec = 6 min 16 sec

FLO 60/90 (2074 grams) : Time on Course : 5 hr 14 min 10 sec
Time Saved = 454 sec = 7 min 34 sec

Ironman Coeur d'Alene
Ironman Coeur d'Alene Bike Course Elevation
Baseline Time
Training Wheel (Heavy Version 2259 grams) : Time on Course : 6 hr 01 min 36 sec

Time Saved by Improving Only Weight
Training Wheel (Light Version 1100 grams) : Time on Course : 5 hr 59 min 54 sec
Time Saved = 102 sec = 1 min 42 sec

Time Saved by Improving Only Aerodynamics
FLO 90/DISC (2259 grams) : Time on Course : 5 hr 55 min 46 sec
Time Saved = 350 sec = 5 min 50 sec

Other FLO Wheels

FLO 30/30 (1624 grams) : Time on Course : 5 hr 56 min 48 sec
Time Saved = 288 sec = 4 min 48 sec

FLO 60/90 (2074 grams) : Time on Course : 5 hr 56 min 11 sec
Time Saved = 325 sec = 5 min 25 sec

Ironman Lake Placid
Ironman Lake Placid Bike Course Elevation
Baseline Time
Training Wheel (Heavy Version 2259 grams) : Time on Course : 6 hr 00 min 11 sec

Time Saved by Improving Only Weight
Training Wheel (Light Version 1100 grams) : Time on Course : 5 hr 58 min 39 sec
Time Saved = 92 sec = 1 min 32 sec

Time Saved by Improving Only Aerodynamics

FLO 90/DISC (2259 grams) : Time on Course : 5 hr 51 min 45 sec
Time Saved = 506 sec = 8 min 26 sec

Other FLO Wheels

FLO 30/30 (1624 grams) : Time on Course : 5 hr 53 min 35 sec
Time Saved = 396 sec = 6 min 36 sec

FLO 60/90 (2074 grams) : Time on Course : 5 hr 52 min 26 sec

Time Saved = 465sec = 7 min 45 sec

The Extreme Courses
For the extreme courses we ran fewer trial runs.  We ran the 1100 gram Light Training Wheel set and the FLO 90/DISC.  Our goal was to see if weight could beat  aerodynamics.

EDIT: I had a few readers asking for additional FLO 30 data.  I have added the FLO 30 data to the Alpe d'Huez climb.  They actually win!


This is one of the hilliest Half Ironman courses in the world.  If you were to turn this course into an full Ironman, you would net 13,434 feet of climbing.  That is nearly 3 times hillier than Ironman Lake Placid!  What wheels do you think won?

SavageMan 70 Bike Course Elevation

The "Un-Aero" Wheels
Light Training Wheels (1100 grams) : 3 hr 20 min 43 sec

The Aero Wheels
FLO 90/DISC (2259 grams) : 3 hr 19 min 39 sec

That's right.  Aero wins again.  Even with an additional 1159 grams (2.55 lbs) of wheels on one of the hilliest courses in the world, aerodynamics will save you 64 seconds.

Alpe d'Huez

So there has to be a breaking point right?  Weight has to win somewhere.  It turns out it does, but you need one of the most extreme climbs in the world to make it happen.  The Alpe d'Huez is one of the toughest climbs in pro cycling.  To give you an idea of just how big the climb is, I superimposed the climb over top of the full Ironman Coeur d'Alene course.  Remember, this climb takes place in only 8.2 miles and it absolutely dwarfs the IMCDA climbs.  Can you imagine climbing this!

The Alpe d'Huez Superimposed on top of IMCDA

The "Un-Aero" Wheels
Light Training Wheels (1100 grams) : 1:09:46

The Aero Wheels
FLO 90/DISC (2259 grams) : 1:10:09

EDITED: The FLO 30s were added after a reader asked to see it.  They actually win by 2 seconds!

FLO 30/30 (1624 grams) : 1:09:44

Even on arguably the toughest climb in the world, aerodynamics only lose 23 seconds to weight.

For the triathletes out there, I think this blog article pretty confidently tells you that, when selecting wheels,  you should focus on aerodynamics first.  I guess in less of course you are racing up the Alpe d'Huez to T2.  Road cyclists, racing TTs, crits and stage races - apart from mountain stages - are also going to save more time 99.9% of the time by choosing aerodynamics over weight.  I don't mean to say that weight has no importance at all, because it does.  I'm just simply stating that aerodynamics helps you save significantly more time then weight.

I hope this blog article has given you enough knowledge to make better decisions come race day.  Partnering with Ryan to create these course simulations was really a lot of fun.  I'd love to hear your questions and comments below.

Take care,



Kim Osborne said...

I think you meant to say "we picked a rider who we felt represented the majority of MALE age-group athletes".
I don't know of many 170lb women who are finishing Ironmans, nor whose FTP is 250W.
The calculated advantages of aerodynamics are overstated for those who don't average in the mid-30km/hr range on a flat course. I'm not saying weight would prevail, but aerodynamic advantages are highly dependent on wind speed, and I believe an accurate article should also point out these limitations.

FLO Cycling said...

Kim Osborne,

You are correct. The athlete we modeled the calculation off of would definitely be a male. I will change that in the blog article. Thanks for pointing that out.

You've mentioned that aerodynamic advantages are overstated for those who do not average in the mid 30km/hr range. This is not true. In fact, slower athletes actually save more time. This is a common misconception because all of the tunnel studies are done at 30mph. Also remember that 30mph is a "relative" speed.

You mentioned that an accurate article should also point out the aerodynamics advantages for athletes based on varying speeds... we've actually already written a couple articles on that topic. You might find them interesting. The first is a general explanation, the second is a more detailed look.



Please let me know if you have any additional questions.

Take care,


Froze said...

I assume that you put the 60 on the front and the 90 on the rear like most people do putting the more aero wheel on the rear? Why? Since the largest amount of air disturbance is on the front why wouldn't you put the 90 on the front and since most of the air disturbance on the rear is being blocked by the frame then the 60 should be on the rear. Am I missing something here? Just wonder what the results would be if the 90 was in the front.

Chris Chaddock said...

So very basically, a disc wheel combination will almost always be the quickest wheelset to race?

What effect do you think reducing the weight of Flo disc's and Flo 90's would have on time?

FLO Cycling said...


Putting a deeper wheel on the front would make the bike harder to control, and I'm guessing with a shallower wheel on the back, this effect would be worsened. I understand your point, but we did not run that configuration. Could be interesting though.

Take care,


FLO Cycling said...

Chris Chaddock,

Thanks for writing. We actually ran a run of a lighter 90/DISC combo for curiosity sake. The lighter set is a little faster but not compared to the difference in Aero vs. Weight. We may work on a follow up article after Order 10 to post on the blog.

Take care,


WilierRMB said...

Great post. how about in a pack? How much can we keep aero wheel benefits in a road race pack on flat?

Hallian said...

Disappointing presentation of results. The Aero wheels save 64 seconds on a 3hr 20 minute ride, WOW etc, exclamation marks, then on Alp d'Huez they ONLY lose 23 seconds. On a 1hr 10min ride?

That's roughly the same margin.

Not standardising results is really a most fundamental error.

FLO Cycling said...


In all honesty, with the number of variables introduced when riding in a pack, it's really hard to estimate the time savings. All of the wind tunnel data, and the data presented in this article assumes that you are the rider at the front. I personally do not have an accurate answer to your question.

I'll see if I can get Ryan Cooper on here to comment on this question. Perhaps he has a better answer.

Take care,


FLO Cycling said...


I'm sorry that you do not like our blog article. We presented the facts as they came to us. We even showed our own wheels losing the battle in one case.

I'll also add that your we did not add "WOW etc, exclamation marks" to our results. You have created that version yourself. We simply stated that aerodynamics won again. Regarding the Alpe d'Huez climb, I did say "only". I used the word only, because I thought it was rather impressive that even on one of the toughest climbs in the world, an aero advantage was still that close (considering on a flat course the difference was 2 to 529 sec). Additionally, if there were any "normally hilly" course before or after the Alpe d'Huez climb, the rest of the article shows that aerodynamics would quickly catch up.

I appreciate your comments. If we were only comparing two courses, I think your comments would hold more weight. However, I feel you have ignored the data in the beginning of the article - the IM courses - and taken my message out of context.

Take care,


Marius Lazarescu said...

Good job guys!

Matt Fieldwalker said...

I think one must be careful to not generalize these benefits to general road racing.

Drafting and the huge importance of accelerations suddenly makes wheel weight matter a lot!

FLO Cycling said...

Matt Fieldwalker,

I will agree that drafting will make a change but I disagree with accelerating. In fact, even when accelerating, aerodynamics drag takes 49 times more force to over come than weight. Weight even when accelerating is really very insignificant when compared to aerodynamics. Don't believe me... read this article here...



KOB said...

Great article! As someone new to the sport I found it very informative. My question is how wheel stiffness plays in to time and energy usage. I just replaced stock Oval 330s with your Flo 30s. While I could feel the weight difference for sure, I'm guessing the aero difference has to be pretty small. I'm hoping I didn't spend $600 to gain a few seconds over my next 100 miles! Thanks.

FLO Cycling said...


Wheel stiffness does play a part in the equation, but without knowing the build specs of your Oval wheels it's nearly impossible to compare the two. Know that our wheels are considered stiff by many people our our build specs are all on part with manufacturer recommendations. We also use Sapim CX Ray spokes which offer some of the best strength and fatigue life available.

Additionally, I do not know of any aero testing done on the Oval 330 wheels. From what I can see, they look much closer to a standard box section rim than the FLO 30s, which means you are likely saving more than a few seconds. Without putting the wheels head to head in a wind tunnel it is impossible to know exactly.

The last thing I will mention is ride quality. I believe the Oval wheels have a 19mm wide brake track. The FLO 30s have a wider brake track which provide a more compliant ride, allows for lower air pressure, and offers better cornering and rolling resistance.

I hope that helps,