Questions tagged [aerodynamics]

Questions relating to a bicycle's ability to efficient move through the air.

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28
votes
6answers
9k views

Does drafting cause resistance to the lead rider?

I know that when riding close to another cyclist, I expend less energy to go the same speed. But does the Conservation of Energy "law" mean that the lead cyclist is going to expend more energy to ...
19
votes
4answers
6k views

What is a “gram” of drag?

Bike components or upgrades are sometimes quoted as saving some number of "grams" of drag. How can a gram, a unit of mass, be used to quantify drag, which is a force? And for extra credit, why is ...
19
votes
3answers
6k views

What are the most significant factors affecting downhill cruising speed?

When I'm riding with my friend, I notice that he rolls down hills significantly faster than me. We can be riding next to each other, both in a similar aerodynamic position, but if we both coast he ...
18
votes
5answers
6k views

Why are road bikes (not time trial bikes) used in many triathlons?

I've been watching triathlon videos lately and I couldn't help but notice that, with the exception of Ironman Competitions, only road bikes and not time trial bikes are being used. Is there any reason ...
13
votes
5answers
8k views

Are aerodynamic rims worth additional weight?

I was under the impression that reducing the weight of your wheels is important. However, I'm noticing that many of the extremely high-end aerodynamic rims are actually heavier than cheaper rims by ...
13
votes
4answers
3k views

What would cause variable air resistance on a day with no wind?

I commute to work regularly. I find that on some days when there's no perceivable wind, I feel like there's almost no air resistance at all and it's so easy to ride at speed. It's also relatively ...
13
votes
1answer
338 views

Why do track bikes vary between events?

Watching the Olympics, I've noticed that track bikes seem to vary between events. For example, in the Keirin, all the riders have bikes with a solid/disc rear wheel and a front wheel that has a solid ...
12
votes
3answers
2k views

What are the disadvantages of wearing an aero helmet?

During the Olympic Final of the Men's Keirin one competitor (Chris Hoy) was wearing an aero helmet (red helmet in the picture below), the other competitors wore normal helmets: The advantages of ...
11
votes
5answers
9k views

Why aren't road bicycle wheels tiny?

My understanding is that air resistance is where most of the pedal power goes to at high speeds, and that this is a concern not least for the wheels: What you pay for in a road bike wheel is ...
11
votes
2answers
12k views

Aero Bars vs The Drops

On my road bike I am debating installing aero bars. Will I notice a significant measurable improvement in speed using aero bars vs being in the drops? I am looking for specific numbers here with ...
9
votes
1answer
1k views

Road Bikes: Aero vs. Traditional

On any given race within the pro peloton, the teams whose sponsors offer both aero and traditional frames (BMC, Trek, Canyon, etc) typically have a mix of riders on each style of frame, but the GC ...
8
votes
2answers
5k views

How come some cyclists lean forward at a 45 - 60 degree angle and I don't?

I just wanted to ask how come some cyclists when they ride they lean forward, with their arms straight, resemble a 45 to 60 degree angle (which looks cool by the way). I have a hybrid bike and I wish ...
8
votes
1answer
2k views

What is the difference between Time-Trial and Triathlon bikes?

Time-Trial and Triathlon bikes differ from normal road bikes in that they are designed for maximum efficiency when riding alone (not in a group). What, then, is the difference between them? Would ...
7
votes
3answers
7k views

At what speed does Aerodynamics of a bike come into play?

Is a more aero bike more efficient than less aero bike at 10mph? At what speed does Aerodynamics affect your speed significantly. update: "The question is dealing with the minimum speed that a ...
7
votes
3answers
1k views

DIY computational fluid dynamics for aerodynamics?

Has anyone experimented with using consumer 3D software to do CFD-like aerodynamics simulations? Specifically, I was thinking: Setup the bike on a trainer (with rider) Take a series photos, and plug ...
7
votes
2answers
3k views

Why choose a traditional frame over an aerodynamically streamlined frame?

I'm not talking specifically about triathlon frames, just frames which have aerodynamically shaped tubes. As I understand it, both types of frame are legal for road-racing under UCI rules. So, why ...
7
votes
1answer
453 views

Accurately replicating the resistance felt whilst riding via a resistance fan diy turbo trainer

If I were to build my own Lemond Revolution style turbo trainer (link below) could I use the air speed in meters/second^2 the rider is moving into as a good indicator of what type and size of fan to ...
6
votes
3answers
2k views

What is the drag / power lost to a safety flag?

I have a recumbent bike that has a safety flag on the top of a thin pole, so it flutters around higher than and after my head. How much power am I losing to this flag that could be used to power my ...
6
votes
5answers
2k views

Riding into a headwind faster than my top speed - how is it possible?

Recently we've had some pretty strong winds here -- today the weather forecast said 20mph gusting to 30mph, but a few weeks ago the gusts were supposedly over 40mph. The forecast direction was within ...
6
votes
1answer
1k views

What's more aerodynamic on flat bars: backpack or pannier?

I'm surprised this hasn't been asked before, but as a general rule, is a single rear pannier or a backpack (of similar sizes) more aerodynamic on a hybrid or MTB? Even on flat bars drag is much more ...
6
votes
1answer
2k views

What is the average CdA to Weight relationship of a professional Road cyclist?

As Body mass increases so does its volume resulting in a higher CdA causing more drag. However CdA does not increase linearly with mass. Are there any posted weight and CdA comparisons out there for ...
6
votes
1answer
906 views

quads feel over used while in an aero position

I typically ride on the hoods, but I've been working lately on a more aero position. When in the drops or using clip-on aero bars I find that my quads get fatigued much more than when I'm in a normal ...
5
votes
2answers
443 views

What's the best way to shield a rider from the wind in a group (most aero position in the group)?

Yesterday I caught up with a much stronger rider who was struggling with an injury but really wanted to finish. Moral support aside, we tried to get him on my wheel on the flats (which happened to ...
5
votes
2answers
2k views

Does group riding negate the aero benefit of deep rim wheels?

I've been weighing up some options over wheels and in doing my research I've noticed that rim depth may be a bigger factor than I had previously considered. On the one hand, shallow rims are typically ...
5
votes
4answers
5k views

Aero bike vs climbing bike for running in Crits

I'm considering building a road bike and getting into running Crits this Summer and I'm unsure as to go with an Aero bike or a climbing (lightweight) bike. Based on my general understanding, when not ...
4
votes
1answer
3k views

Climbing or aero bike for a light rider?

What is the better choice for a lightweight rider (173cm - 48 kg), lightweight climbing bike to get even bigger edge when climbing, or an aero bike to catch up the speed in the flat road? Obviously I ...
4
votes
3answers
1k views

How much aerodynamic drag does each component contribute?

Obviously numbers will vary based on the specific bike, but what are some approximations of the drag contribution of individual components in a typical (non-aero) road bike? I have read in many ...
4
votes
2answers
450 views

CdA of a bike without rider

This question at aviation.se got me calculating the acceleration of a bike strapped to the outside of a plane if the straps broke. As you do. I couldn't find a figure for CdA of a bike without rider ...
4
votes
1answer
113 views

Independent ranking of bicycles aerodynamics

Are there any scientific and independent evaluations of different bicycles from an aerodynamics perspective?
3
votes
3answers
364 views

Is there any benefit to riders on the front of a paceline? [duplicate]

You can save a lot on air resistance by drafting a rider closely, i.e. riding close to their rear wheel. What about the rider in front? Is there a benefit, a loss, or is there no difference? Edit - ...
3
votes
3answers
1k views

What sort of bicycle helmet gives me better speed?

I am working to improve my segment times on Strava riding 10km to/from work. My average speed is 32 kmph, and over short segments (1km) I can set avg speed 44 kmph / max 49. Over the last year I ...
3
votes
2answers
818 views

Effects of longer and higher stem on rider position/comfort and handling

My first road bike, and the bars feel a little low and a little close. What would be the effects of switching to a stem that is 10-20mm longer, and either the same angle so the bars are slightly ...
3
votes
2answers
165 views

Anti-aero resistance training jerseys?

Is there any manufacturer that makes specific anti-aero training jerseys for increased effort at lower speeds? Sort of like a braking parachute but more practical and subtle? My reason for asking is ...
3
votes
3answers
4k views

What is the best aero position in a mountain bike?

I'm familiar with TT and road bikes with aero bars. However, I don't know what is the ideal aero position for a normal MTB (no aero bars). I did some search and found these pics. Hands on the middle ...
3
votes
1answer
242 views

Road bike drag decrease with bulky backback

I'm about to increase my daily commute from 5 km each way to 10 km each way. I've been using a MTB converted to a commuter for years. Given the extra distance, regular evening head wind, and aging ...
2
votes
4answers
851 views

Does riding a cyclo cross bike carry a large aerodynamic penalty when compared to a road bike?

During club rides I find myself getting dropped by riders with the same weight and power but the main difference is that they are riding road bikes and I am on a cyclo cross bike (with road tyres and ...
2
votes
2answers
699 views

Why do deep section front wheels get pushed around in crosswinds?

If a bike with a deep front wheel or a front diskwheel were to receive crosswinds with a 90 degree yaw angle handling would not be affected since the pressure would be equally distributed among the ...
2
votes
4answers
1k views

Thoughts about tri bar / trekking bar on hybrid bicycle

I have an hybrid bicycle Firefox Rapide 21S. I ride regularly around 40 KM. In headwind I feel like I should be in aero position so sometimes I put my elbows on my handlebar and it helps to reduce ...
2
votes
3answers
323 views

Can it be estimated when it would actually be beneficial to increase drag in tailwind?

Usually the advice for cycling is to try to be as aerodynamic as possible (like, reduce the surface exposed to the air in front of you) in order to decrease drag as it will cost less effort to ...
2
votes
1answer
5k views

How can I move the saddle further forward?

Recently I bought a clip-on aero bar for my road bike and has been practicing aero position for triathlon. I read that moving the saddle forward could mimic the triathlon bike geometry. However, I ...
2
votes
2answers
637 views

Does fitting mudguards / fenders improve aerodynamics?

Since the tops of the wheels are moving at twice the speed of the bike, you would think that covering them up would make quite a bit of difference to the drag coefficient, particularly the front wheel....
2
votes
1answer
159 views

Aero bike considerations for purchase

I am trying to decide between aero bikes from two different brands. What are some of the things I should think about when comparing these two (or any other) aero bikes?
2
votes
1answer
878 views

How much better are aerodynamics between a vintage road bike and a top of the line aerobike?

(Just up front: (1) All comparisons made keeping all other factors equal! (2) I know this is a really hard comparison, but there seems to be virtually nothing canonical on here or the rest of google, ...
2
votes
1answer
2k views

How do I choose a light GPS device supporting Strava? [closed]

Up til now I have ridden with Strava running on my mobile phone sitting in a special mobile phone holder which sits up on my handlebars. Now I am looking for a better solution, both more aerodynamic ...
2
votes
1answer
146 views

Does hub diameter or hub size have a notice able effect on the aerodynamic performance of a wheel set?

If you were to change the rear hub on your hypothetical or real zipp 808 wheel set to a large diameter internal gear hub like a shimano alfine or a rohlhoff hub would there be a measure able aero ...
1
vote
6answers
1k views

What position of saddle is best?

Almost all cyclists who ride road bikes set the seat so high, and when they're in the drops their body can be almost parallel with the road, reducing air resistance. However,their legs can't reach the ...
1
vote
2answers
233 views

How close do riders follow their wheel/attack

How close do peloton riders typically and strategically follow each other's wheel/attack? Also, how is this distance manipulated in order to allow for strategic movements or a more aerodynamic ride.
1
vote
1answer
398 views

Why am I not seeing improvement in my bike split time?

My training went up significantly between half-iron events. There was improvement in the swim and run. But no improvement in the bike... In fact I could say I did worse because there was little ...
1
vote
1answer
1k views

Advice on aero wheels

I have decided to buy new wheels for this season. I'm currently riding the Bontrager Race Lite wheels that came with my bike, and now it's time to move to aero wheels to keep up. I'll do about 1300 km ...
1
vote
2answers
3k views

Crosswind effect on an aerodynamic front wheel vs a rear wheel

I am looking to purchase a new wheelset in the not too distant future and am debating between wheels that are 58mm and 85mm deep. Or, and this is the part I'm curious about, a hybrid of the two. (58 ...