Aero Deep Dive in The Specialized Win Tunnel – Ask a Cycling a Coach 188

aerodynamics

#41

Really great episode with a lot of interesting insights.

I have a non-aero Trek Emonda SLR. It would seem aero wheels and a aero handlebar would give a big boost in terms of aero-efficiency, even on a “non-aero” bike. While it likely won’t approach a Venge or Madone for “aeroness”, it may be a decent trade-off and still have a really light bike. I do have carbon aero wheels (although not super deep ones) but after the podcast I’m really thinking of putting on an aero handlebar/stem combo.


#42

I have a little trouble with the talk of “saving” 5 watts or 20 watts concept. Is that watts from a certain amount of time or a whole ride? Or is that saving relative to the FTP? If someone could explain that would be great.


#44

Think of it this way:

As a preface, all of the numbers in this example are made up. So, if you are riding into the wind and you are not aerodynamic, you will have to put out 255 watts to go 15 miles per hour because you are working against the wind more than somebody that is aerodynamic is. BUT… If you are aerodynamic you can maintain 15 mph at 250 watts (instead of 255) because the wind resistance is not slowing you down as much and causing you to work harder to maintain that speed.


#45

We have almost all our professional riders on clinchers now, not exclusively for every race (cobbles for example) but it’s in the arsenal when appropriate.


#46

I’m bother by people being bothered by 40 or 45 kph testing.

I am far from elite but average 41-42 kph in the bike leg of a 70.3 ironman. I am a good bit faster in a stand alone TT (46-48) but I’m far from elevate. I barely can make a cat 4-5 podium in my area at that power.


#47

@Superdave is Dave from the podcast!! I feel like we need to do just an episode with Dave about “aero tricks”. I had some off-camera talks with Dave and learned a ton! I’m not sure what I can share and what I can’t though.

Dave, what are we all doing wrong (in general)?


#48

This was a fantastic episode. It ended way too quickly!


#49

@Nate share nothing with your competitors and share everything with your teammates. As for your readers and viewers? Maybe it’s time for a subscription service for the good stuff

In general, the performance sins I see most often are:
Poor fitting clothing
A lack of practice getting into an aero position. You needn’t turtle your head and roll your elbows in and flatten your forearms for the entirety of a 3 hour ride but certainly find that sweet spot for the 10-15 seconds you’re pulling thru in a paceline or chasing on.
Proper tire selection for a rider’s size and event choice and using way too much air pressure. Crr penalties can easily rob 20w while offering no benefit. You can find MTB tires with less rolling resistance than some road tires. Spend money on latex tubes, not carbon bottle cages.

Some nitty gritty stuff that riders can fix in seconds:
QR placement
Cable length and management: -10cm of 5mm diameter housing can be ~1w
If you must carry tools put your kit anywhere but in a large seatbag: behind the stem is best ~95% of the time

-SD


#50

Why are aerodynamic benefits always expressed as watts savings at a certain speed when a much better metric would be % increase in speed?

Why do I ask that?

Well the number of watts that are saved depends on the amount of watts being produced in the first place which is obviously dependant on speed:

Lets say a rider was producing 360 watts at 45 kph (that’s a CDA of 0.3, assuming no other resistance). A change to the setup saves that rider 36 Watts at the same speed, or 10%. That’s a 10% reduction in CDA to 0.27. But who wants to go the same speed at lower watts? By keeping the power output the same the speed can be increased to 46.61 kph, a 3.57% increase in speed.

Now take another rider at 40 kph but with the same CDA. They are only putting out 252 watts. By making the same changes the CDA is reduced by 10% to 0.27 but the power reduction to hold the same speed is only 25 watts. Not such great marketing, even although the increase in speed is exactly the same at 3.57% (from 40 kph to 41.43 kph)

The reality is that a 36 watt saving sounds great to a rider with an FTP of 250 even although I’d never see those numbers in the real world.

Mike


#51

What do you think of Enve’s pressure recommendations?

Which ones??? :smiley:

What about tubeless? I hear it’s on par with latex in most cases (or a bit faster).


#52

Schwalbe Big One. Great tyre for gravel racing.

Mike


#53

Only if the packaging is aero.


#54

I have the same set up on my Emonda – stock cockpit w/aero wheels. Will have to do some calculations to see if the watt savings are worth the dollar spendings. :man_shrugging:


#55

Thanks for the explanation!


#56

At 200-210+ lbs my experience says respect them:

see last pic. No cell coverage and 10+ miles from civilization in a national forest…


#57

Thanks for all the insight Dave.

Are you able to expand on the seat bag? Obviously going to vary for all situations but if you had to gauge, is that closer to a 1W difference or a 10W difference? Or is it one of those situations where skipping the seat bag is just never going to make you slower?

Thanks!


#58

I understand a saddle bag is a great place to store stuff and for a round post and a small bag the penalty is going to be small, but I’ve never seen a saddle bag that was designed to improve airflow. On the other hand, our own Aero Pharaoh Mark Cote developed storage behind the stem way back in his MIT days, I think he first showed me a prototype in 2006! In many cases filling in the recirculating air behind the stem’s abrupt steerer clamp can reduce drag. It also makes getting into the bag easier. I’m sure we could show a 10w net difference, maybe double that in a worst case to best case swing


#59

Do you have a picture example of storage behind the stem?

Assume a small frame pump is a disaster as well on my Roubaix. :slight_smile:


#60

I have a Prevail 2 helmet which i love, I do wear a buff underneath to stop my head getting burnt from sun. Does wearing something under your helmet such having a buff have an effect?


#61

I’d love to see a video or some photos with examples of good/bad practice here. Particularly for those of us not fortunate enough to have a fully internal cable system.

Thanks for all the good advice!