woodcraft

It is a sequitor to Psimet's point about equipment marketed as "seconds saved in a 40k TT"

Hermes

I read his comment and rolled my eyes. There is a devious side of me that thinks promotion of idea that equipment selection makes no difference in racing and the best racer wins is perfect for my competitors. I think OP is smart enough to make the right decision based upon his budget and independent due diligence.

Hermes

@RChung is the guy to discuss this from a technical view. When one rides solo, the airflow is different off the front and generates more drag force than airflow in a pack but the effects are more complicated to quantify. So one gets some benefit of aero "stuff" sitting in a group. Where aero equipment and clothes yield the most benefit is solo riding and small breakaways. So a breakaway artist is going to favor aero equipment or at least see more value than let's say a sprinter who wins via a lead out train from the pack.

wphamilton

@Hermes You have laminar and turbulent backwards, but that doesn't invalidate what you'd said here. You might want to edit it.

asgelle

Actually, I think he has laminar/turbulent confused with steady/unsteady. At normal cycling speeds, all flow past a bike is fully turbulent (Re O(10^5)). Riding alone on a still day, the flow will be steady, in a pack it will be unsteady as the flow coming off other riders swirls around. On a day with wind, even riding alone, the flow is likely to be unsteady as wind shifts/gusts, trees, buildings, cars, etc. affect the flow.

Hermes

I am not sure if I have it wrong or not quite right.

"In fluid dynamics, laminar flow occurs when a fluid flows in parallel layers, with no disruption between the layers. At low velocities, the fluid tends to flow without lateral mixing, and adjacent layers slide past one another like playing cards."

At the indoor velodrome, the air is almost still assuming no other riders on the track and low velocity. In general, outdoor airflow will be lower velocity and will have some turbulence just because of the ground effects but in general, it will not be as turbulent as riding behind a motorcycle or in a pack of cyclists.

"Turbulent flow, type of fluid (gas or liquid) flow in which the fluid undergoes irregular fluctuations, or mixing, in contrast to laminar flow, in which the fluid moves in smooth paths or layers. In turbulent flow the speed of the fluid at a point is continuously undergoing changes in both magnitude and direction."

At the indoor velodrome, the air becomes turbulent when a group of cyclist start riding on the track. It is full of eddy currents and cross currents.

Chung is the guy to discuss this.

asgelle

In a velodrome the air is still, but the bike isn't and when looking at drag on the bike, we should be working from the perspective of the bike, not the velodrome.

The transition from laminar to turbulent flow occurs at a Reynolds number of around 2000. Reynolds number is a dimensionless quantity describing the ratio of inertial to viscous forces and is defined as UL/nu where U is a characteristic speed, L a characteristic length, and nu the kinematic viscosity of the fluid. So in order to define the Reynolds number, it isn't enough to define the fluid and it's speed, but also a characteristic length. That choice depends on the question of interest. So to use the velodrome example, if you're interested in heating or cooling an indoor track, it might make sense to use slowly moving air ~1m/s and a length of ~150m. However, if you're considering drag on a bike moving around the track, you would use the speed of the bike ~11 m/s and the length of the bike ~2m. For those parameters in air, the flow is fully turbulent.

wphamilton

I figured that's what he meant, that the air is disturbed ("turbulent") in the pack, which it is. But turbulence is one of the causes of drag over the body, laminar flow reducing drag other than parasitic drag but that's another story. Which is backwards from what he was expressing so I figured he'd want to reword it. Not looking for "gocha's" here.

asgelle

wphamilton

OK I get that. I have the feeling it still might not be clear here so to simplify, hopefully, "turbulent" when we're talking about laminar flow over the body (or flow separation from the body) isn't exactly the same thing as "turbulent" air swirling from the bike in front of us. Same word, two different things. Turbulence behind us, swirling air, slows us down and that's reduced in a pack. As well as the air that everyone in front is punching is moving forward relatively.

If we're instead looking at the shape and surface of the body moving through air, we have to consider that boundary layer, reynolds number, and so on but that's not so important to the drafting thing. The bottom line, which I think Hermes was expressing, is that whatever advantage you get from aerodynamics riding solo you also get, in about the same proportion to your effort, when you're riding in the middle of a big pack.

asgelle

Campag4life

Me too. Psimet right again and no surprise the interpolation king Chung a distant last in the race to the truth. Kidding Chung. You are my favorite math interpolator...lol.

To buttress why Psimet is right and why the bike may matter less or more...

I rode with a girl friend yesterday. She is the fastest girl in my town. We are friends. She is 5'5" and lays her body flat on the top tube. No surprise, built like a pro rider...skinny upper body and legs of an Olympic skier. I am 6'1" and don't lay my body flat on the top tube because I can't bend over that far. As a sidebar, she rides only to heartrate. She picks a heartrate target. About 150 bpm correlates to 21 mph for her over the long haul. For me...and I am old, my heartrate is higher. I have to work a bit harder at her pace. Mine is about 162. I can ride faster. But not as far.

When out on a ride we average about 21 mph...a bit more downwind and a bit less into the wind and about 21 mph with side wind. That is how she trains and if I want to ride with her, that is how fast I must ride to keep up.

I catch a lot more wind than she does. So if her watt output is 200 watts at that speed, mine is probably 240 watts or more. I am not a very aero rider. This is what I think about on the bike when I ride with her. She pokes such a small hole in the air and I don't.

I ride a bigger frame size than she does with taller head tube. But moreover, the ratio of rider Cd to bike Cd goes out the window when you compare her to me. It ain't 80/20 for each of us. Can't be. There is no 40 seconds saved in a 40km maximum effort for 'both of us'. This is Psimet's point I believe even taking the guile and cunning (Armstrong) out of the bike race. Physics aren't the same between riders. Bike sizes are different. Moreover the ratio of rider Cd to bike Cd...this generic 80/20 ratio is different. For me based upon how I ride it maybe 85/15 rider/bike and her's maybe 70/30. So if each of us go from the same brand bike...say a TCR to an aero Propel, we each aren't going to save 40 seconds in a 40km maximum effort because our relative ratio of body drag to bike drag is different.

For a rider like me, my body is a bigger drag component compared to the bike. I get it done on power (gearing and cardio). The bike matters less. Yes the bike still matters. But the point is, per the R Chung fallacy, the savings isn't the same for two different riders when say talking specific frame tube shape change for each.

Above is physics. Math guys tend to be not as good at physics. Engineers are better at understanding it. What Psimet is who btw is a very smart guy most know and a keen student of the sport. He lives the hardware.

Also as discussed, psychology of a bike rider is key. When I ride with this girl, I make a real effort to not get dropped. I don't like her dropping me. I ride probably a bit above my typical range to keep up. She trains harder and longer than I ever do day in and day out.

But moreover what Psimet wrote about the strongest rider winning the race is so true. Most of us that care about speed know this implicitly. Most of us ride at a club and many of us here aren't the fastest rider in our group. I am middle of pack aging A-group ride guy. Yes, I try to keep up with the fastest guys who are my friends. We compete in the sprint. The fastest guy...'no matter what bike he brings to the ride'...skin suit or not...what helmet he wears...is ALWAYS the fastest guy. Yes he does a lot of things right on the bike and why he is the town champion but...he has a monster motor and why he beats everybody.

rubiksoval

I've never won from a solo break in my life. In 11+ seasons, I think. I fancy myself more of a sprinter, especially a reduced field/small group sprinter. But I'm about as aeroed out as I think I can get. Why? A few seasons ago I lost something like 7 different sprints (either field sprints or for the win) by a wheel or less using an aero bike but regular al bars and wheels. Next season, 58mm wheels, aero bars, and 165 cranks to get a lower, more aggressive position and I lost only one sprint by less than half a wheel (ironically in a race in which I had to take a shallow al wheel from the pits halfway through, though I was out of position in the sprint.). That's all anecdotal, of course, but...

The strongest rider does not always win, nor does the fastest. I'm certainly neither of those things. I generally barely get much above 1300w in a race. The person who knows how to win usually wins, and that's through a combination of position, timing, and tactics. But that doesn't mean there can't be a myriad of technical improvements.

That's not to say I don't agree with the common sense response of an aero advantage not helping some pack fodder guy suddenly win a race because he went super aero, but you can't just up and decide physics don't exist. I have multiple races a year decided by inches. If a wheel or handlebar (I even have a tri-rig front brake) or the combination of every other thing I do gets me a couple of inches, then that might just get me on the podium, or on a better step.

Campag4life

You forgot the placebo and confidence you got by adding that aero schwag. Kidding. No disputing what you wrote. Aero matters.

But what is complete BS is..for the reason I explained, an aero bike...the same aero bike and aero wheels will not save the same amount of time for one rider to the next for the same bike change. This is where marketing is bogus. As Psimet wrote, a given time change for an aero improvement...say deep Zipp wheels versus box section Open pros...a certain time change at the end of a distance will matter more for the smaller rider..because the bike is a bigger component of his/her drag.

As I recall you are a smaller rider. For a guy like you who doesn't have big power although 1300w sure ain't chopped liver for a smaller rider, your aero equipment will matter more. There is a reason Cavendish doesn't post his power nos. He gets it done on low drag. His small body is barely off the ground. Your equipment is a larger percentage of your total drag compared to your smaller body like him. I have ridden with...and you have too...guys that are as big as a house. Massive guys that put out massive watts. Their body is a much bigger component of their total drag compared to the bike. A bike change matters less to a larger rider.

But, no disagreement that aero matters. Of course it does. Mostly rider but bike too. Percentage of bike contribution depends on rider size and wattage.

Bigger mystery of the universe is why Cavendish being a flyweight can't climb and win the TdF.

rubiksoval

I'm 165, so my power to weight is not (relatively speaking) great, but it's not bad, either.

Cavendish has posted his numbers, though this was from near a decade ago. He's around 69 kgs. But yes, he gets low. Though not as low as Caleb Ewan!


Read more at https://www.cyclingweekly.com/news/m...3b4lP2fWXuv.99

If memory is correct, I think his threshold w/kg is only in the 5.5 w/kg region, so yeah, won't be taking any mtn pass victories.

Campag4life

Great Cav interview thanks. The best make it look easy but it is anything but. What he says, its an equation. Same thing when I asked the best rider in my town. How do you go fast on a bicycle? He says its an equation. Everything matters.

colnago62

Campag4life

And of course in track and on the road fit not only affects power output to the bike...but body position and drag and therefore aerodynamics.

The rider is far and away the most important element when it comes to aerodynamics. If you guys ride with small guys and girls who can ride a bike fast, this is most apparent.
Aero drag of a Lotus versus a Kenworth....takes a lot more power to push the Kenworth through the air.

And interesting dynamic of cycling..even taking into account the specialty of sprinting...how both big and small riders can be great sprinters....Cav versus Kittel for example. Most are big strong guys but there are exceptions. Not so for climbing however. That big body is gonna cost you dragging it up the hill. In some ways it is part of the fascination of cycling. How different body types can compete. There is one guy in our club that has to be 50 lbs overweight. I ride in FL and of course its flat. This guy has massive speed on the bike and he looks out of shape...lol. He can power on the flats. One of the freaky things about him is he is not only fat, but uber flexible. He can lay that big belly right on the top tube and hammer. Cycling. Why we love it.

Bandera

What's the equation to determine the difference in time between two 'cross race bikes identical except for a 500 gram difference in wheels weight performing a series of dismount/shoulder/run through mud/re-mounts accelerating to 'cross race riding speed and slowing to dis-mount speed over a single lap? Probably pretty complicated but according to my analog shoulder-meter I'll take the light one, if it won't break.

-Bandera

Abe_Froman

That's just ridiculous. It's the red one. Especially if it has a cup holder.

Seattle Forrest

A cup holder on a bike? Are you looking for the trip forum?