Help a Pro prep for first trip to the Wind Tunnel

[TriSki20]

Hey everyone, I’m going to the A2 wind tunnel here in the USA for the first time in a few weeks with the goal of minimizing CDA for the '25 season across 70.3 and Ironman. I’m a front pack cyclist and I think it’s finally time… I hope this will take things to the next level as I chase the small gains.

I want to test:

1. Aero Position: stack height, reach, and bar angle
2. Bottle Placement (BTA, frame, behind the saddle)
3. Helmets
4. Calf Sleeves vs. Skin

I will not test different race kits (sponsor, Wyn CDA kit) or shoes (S-Phyre PWR 903).

A few questions:

1. What order should I do these tests in to maximize efficiency? Because once you change position, it then changes wind flow (so helmet A could be faster in position A vs. B, but then helmet B could be faster with position B…). How do you account for this?
2. What kind of “leg tape” were Magnus and Laidlow using in Kona on their bare skin, and how can I get my hands on testing this in the next few weeks?
3. Bottle position testing: I don’t want to waste time screwing/unscrewing things for an hour for the bottle testing. I was thinking about getting double sided velcro tape / gorilla tape and jerry rigging different bottle stacks and angles. Is this going to get me close enough or should I try to really prepare with all the needed variations of 3D printed mounts and such (to angle bottles down, add the downward pointing aero bottle that Patrick used in Kona…, somehow set up a triple bottle in the rear like Magnus in Kona). Seems like a lot.
4. How many hours in the wind tunnel do you think this will take to “get right”? It’s $600/hour and I’ll spend however long I have to there.
5. What else should I be asking that I’m not already?

Here is my current fit vs. Laidlow and mostly who I’m trying to copy (come up and out a little bit, experiment with bottles, etc.)

Bottle positions - what am I missing?

BTA: one 950mL (large) bottle (current race setup)
BTA: 2x large stacked bottles, 0 degree angle.
BTA: 2x large stacked bottles, angled down (marquardt / laidlow kona copy)
BTA: large bottle with elite aero bottle angled down (lange kona copy)
Aero frame bottle ON vs. no frame bottle at all.
Rear behind the saddle - 1 angled rear bottle (current)
Rear behind the saddle - 2 stacked angled rear bottle (vertical stack)
Rear behind the saddle - 3 angled rear bottles (Magnus Kona setup)

Helmets. What am I missing? Is this too many?

Giro Aerohead
Kask Mistral - M and L
POC Tempor
HJC Adwatt (current helmet)
S-Works TT 5
Rudy Wing V2
new EKOI
Abus Gamechanger
MET drone
Aerohead 2 (Jumbo goofy helmet, if I can get my hands on one)

Legs:
Bare skin
Wyn Calf Sleeves
Skin with “aero” tape (i.e. magnus / laidlow in kona)

Thank you!

[JackStraw13]

Paging DesertDude

[burnthesheep]

Personal aero hobbyist opinion….don’t spend too much time on the bottles.

Helmet wise research online the generic “top 4” based on what fits people pair them with. I would do more bike fit stack reach angle stuff then borrow an outdoor sensor after maybe for helmets if budget is a concern.

Even being an outdoor only guy couple years ago I had to optimize the hardware changes to not be out in the sun swapping hardware. Figure out a tool kit and fast change process.

[desert_dude]

First off I’m hurt you didn’t hire me to do your testing. hahaha just kidding. I have spent a few hundred hours at A2 testing over the years.

Actually last year is the first year in near a decade where I did 0 hours at A2 even though I did well over 150h of aero testing last year. Typically I start with field testing then can take people to the tunnel to answer the questions that we can’t answer in the field due to the margin of error.

You need a plan. Having someone who is well versed in aero testing, who can modify the plan based on the results, who can stop you from going down the rabbit hole will save you time and money. Plus help with the wrenching. It’s easy to go down the rabbit hole. Remember that each minute is minimal $10. Each run is going to take you 3-5 minutes. Then there is wrenching time and the clock doesn’t stop.

Set a time budget. ie 3h 4h and stick to it. You can go down a rabbit hole, very easily, with just 1 more run, then 1 more run. It’s super easy to get mixed up on the order to test, what you want to test, was run 11 faster than run 15 and if so at 0 or at yaw and on and on. Do you even know what yaw angles you want to test?

It’s really hard to test yourself, ask me how I know. I can recommend someone in NC if you want. It’ll probably add $150-250/hr to your testing. Or you can fly me in.

Your list makes my head hurt, too many options. You’re going to spend $3-6k testing all of that and Geoff has been reluctant to spend 10h at the tunnel these last few years. It’s no fun, even for the test subject.

Don’t worry about mimicking anyone’s position. Develop your position. If it tests fast for him it could be horrible for you.

Have your position dialed in before showing up, then tweak that or have at most 2 maybe 3 distinct positions (say +50mm more stack and -30mm stack from baseline) that you want to test, go with the faster position then tweak it.

Position position position. Everything else is going to save a couple of watts here a couple there where as your position can be 10-12-15w

Leg tape - that’s the last thing you should be worrying about. Don’t pick the small apples off the tree

Bottles - again that’s smaller fruit. Position, helmet, clothing. I suspect some of what you’re seeing in the pro field hasn’t been tested.

take a reductive strategy. Start with everything on there, then subtract. That’s almost always faster than trying to add.

Also A2 doesn’t have a great selection of helmets anymore, a lot of older helmets. They have the Aerohead and Mistral off your list.

Hope that helps

[theyellowcarguy]

Great choice, can’t wait to see you win one.

I’d err on avoiding the leg tape, Laidlow lost 3 of 4 I believe and Ditlev’s appeared to be flapping in the wind because they were loose.

I’d personally go for big fish this time and maybe come back for refining after learning more. For example, maybe pick 2 or 3 bottle setups to try. But focus on position and helmets which will likely have significant gains potential.

I’d also only go if you bring an expert if you don’t have one lined up yet. I can’t tell if desertdude is joking or not but him, Heath Dotson, MarcG are highly recommended here.

[desert_dude]

I’m always available for aero testing.

[stevej]

Justin - can those FW bars even be adjusted for more reach, stack, and angle?

If you haven’t already, you really need someone to coordinate and guide you through the testing. Let alone do the wrenching in between runs. And that someone should have a good amount experience in aero testing.

Why not do outdoor testing? Either with desertdude in AZ or Jim Manton at Ero. Both are a lot closer to you than NC. You could fly in marcag as well and do it in Vegas.

I would stop trying to emulate what others have done. That’s a slippery slope and a game you will never win. Everything is individual and you can’t allow yourself to chase a certain number (cda). At the end of the day, you still have to bike 56/112 miles in the position and run after. There has been a number of people come on here and post about their wind tunnel session only to see them change their position a few months later because they couldn’t hold the position comfortably. You need to let the testing dictate where you go (with someone experienced guiding you) although you need a high level plan and strategy going into it.

Lastly, your first go round should be about finding the bigger things which is typically position, helmet, and suit. Once you optimize those, then you can get to the smaller stuff like bottles. But realize you may run out of time and never get to that.

Realize that you may come out of the session with more questions than you came into it with.

[jimatbeyond]

Have you considered shorter cranks and more reach?

[TriSki20]

Thanks everyone! Some super helpful responses.

Position and helmets - got it.

It is very clear I shouldn’t go alone - noted. I will see who the A2 team recommends (they have a “local fitter / coach” service that is super cheap) although I’m certainly not against flying someone in with me and spending more $. I want to get this right. I’m currently taking bids Or suggestions for someone that is driving distance near NC and doesn’t need a flight and hotel…

1. Position. I love my position now and am super comfortable and pushing higher power than ever this year without issues off the bike (well, some issues, but not bike fit related lol). So I’m going in “hoping” I don’t need to make big (or even any) changes, but I am open to it. I figure the first thing I’ll do is raise and lower the stack height a bit like DesertDude suggested. Then I’ll come out a bit, as I think I could get my head a little more “snug” with my arms if I do so maybe. Then I’ll mess with a couple of angles of the aerobar. Although this bike fit part is probably where I’ll need the most help and guidance. I have 155mm cranks and could come forward on the saddle position but will need more reach.

Bottles: my baseline test will have one BTA bottle. Then I’ll do a second test with a second bottle, then a third test with the double bottles angled down if that’s faster.

For those asking why I’m not doing outdoor testing, there are 2 reasons. One, I already have, and but couldn’t really get a clear reading on some of the smaller things like bottle placement, several different helmets that all read very similar values, and 2) I can’t change my position at all with my current setup. I have FirstWheel custom titanium risers and a monobar based on last year’s fit. But, I have a custom “testable” riser setup coming designed specifically for the wind tunnel (that isn’t rideable outside). And then FW will get me a custom setup with the “new” titanium risers based on a new position if necessary.

I’ll probably pick 5 helmets to test after locking in the position. I may only be able to get my hands on about 5 of those anyways…

I’m not sure how the wrenching will work on the “testing” setup but I assume it’ll be pretty standard.

Will skip the leg tape tests and just take off the calf sleeves if I have time for one more at the end and see if I lose anything (will do baseline test with them on).

Will try to stick to 3 total hours.

[Mulen]

In your comparison with Laidlow, even if he is on top of his pedalstroke, and you are already on the push-down, then Laidlow´s hip angle is somewhat more open.
I would look into opening up that angle more!

Chime back in when you are done with testing - could be interesting to see what you achieve! Thanks

[JTri1234]

Those are images almost guaranteed to be from slightly different camera angles and you’ve drawn different placements of the shoulder, hip, and knee joint centers between the two athletes. Not that a human could eyeball functional joint centers anyway. Any one of us could redraw those lines and get 10 different angles 10 different times. Plus, this is an off-angle sagittal view of the athletes. Hip flexors and glutes work on a literally externally rotated axis of rotation due to pelvic and femur origin and insertions so even a perfectly orientated sagittal camera wouldn’t tell the right story as far as the joint’s functional angle. Far better off comparing an angular range based on an obvious and unchanging anatomical landmark (with a consistent camera angle). Even then, different hip flexor/glute/quad origin and insertions will influence one athletes ability at a given 12 o’ clock hip angle and vs. another. It’s impossible to know an optimal angle without strength testing at various positions. Would require an isokinetic hip/knee/and ankle setup rotating at the athletes preferred cadence through their potential range of motion. To my knowledge nobody is offering that service to the public.

For the rest of us: if the angle hip angle is comfortable, try getting more aggressive. If that saves you drag and isn’t uncomfortable, great. If it doesn’t save you drag, sit up. If it’s uncomfortable but has less drag, then the athlete has a decision to make.

[Mulen]

@JTri1234
The point was: If OP wants to mimic Laidlow´s position (which I did not say is optimal for him necessarily), he would initially need to work on opening up the hip angle and look for sligthly more reach.

[BenwGoodfellow]

@TriSki20

I have a custom “testable” riser setup coming designed specifically for the wind tunnel (that isn’t rideable outside).

Would that be something along the line of this design? Makes loads of sense for making quick changes while testing in a wind tunnel.

Also debating doing a first wind tunnel visit. Be very interested to hear how you get on and what you would do different in future.

[marcag]

@BenwGoodfellow

Also debating doing a first wind tunnel visit.

You are lucky to have access to Silverstone. It’s a good tunnel and there are competent local resources around to help. You just need to identify them.

Personally I would not do an extensive tunnel test without proper guidance. “Proper” is the key word.

[JackStraw13]

Hopefully there will be a YouTube documenting this process.

[marcag]

Kind of a side bar, I just found THE coolest youtube feature

Youtube autotranslates youtube videos in other languages.
This is Benito Lopez. I kind of got the jist, then I figured out the Captions can be turned on and autotranslated. CC button turns them on, settings sets the language

Sorry for the side bar.

Ahorrando Watts | ft. Uniqo Custom Bikes & Ciclismo y Rendimiento

[michael_Hatch]

I have no expert knowledge to give. But I do notice you are quite deep on the saddle compared to Laidlaw. And you might want to take a look at Jackson Laundry and his saddle position, which is quite dramatic but opens up the hip a lot. He’s a fairly good biker from all accounts.

[desert_dude]

Shoot me a message, maybe we can work something out or I can make recommendations that would be better than the local fitter who doesn’t do a lot of testing anymore and tends to work with cyclist 5-1 vs triathletes.

Outdoor testing is great for answering a lot of questions yet the sensitivity is a few watts. The tunnel can answer those questions where outdoor testing can’t. The is this 1 or 2 w faster than that. To do that outside you would need a ton of runs to get a (more) clear answer.

There are drawbacks and benefits to both. Yet I think for position testing starting outside allows you to dial it in so you’re not spending 30 minutes aka $300 answering a stack question or reach question. The wind tunnel allows you to answer is 10mm or 15mm reach better or is adding 1.5 or 1cm stack better. That’s where A2 shines.

3w is real world watts, 1w is when you’ve solved all the 3w problems.

The wrenching/aero expert help is so you don’t have to get off the bike, run/walk to the back of the tunnel, check with Geoff to see what the numbers say, think about what to do next, grab the tools & parts you need, then get on with wrenching/measuring everything then going back out of the tunnel to put everything away in the tool cart, grabbing the next items to test, placing them to be tested, then going back to your bike, hopping on and holding for zero. Easily save you minimal $40 per thing you test by having someone else there. FWIW the longest change I’ve ever had was 17 minutes with 2 of us wrenching on the bike. The average change is probably about 5min.

In 3h if you’re good at what you do you can get through minimal 15 configurations, max of 24 if everything goes well
(15x$40 = 600 which is an hour of testing or by having someone there you don’t test 2h paying for 3)

Anyway hope that helps. And FWIW I stay at my Dad’s and drive to the tunnel when I test. Hanging out Dad > hotel 17/10 times.

[marcag]

@TriSki20

Will try to stick to 3 total hours.

I went to Silverstone last month with 2 pro riders. We tested bike frames, cockpits, positions, helmets, suits, wheels and tires. It was intense.

You can do it on your own, as I did the first time I went to the tunnel. BUT, you will probably get a fraction of the value if you get some help from a competent person.

When we went to the tunnel, we had a mechanic, myself and a set of helping hands.

I made a ‘run schedule’ that we all agreed on. For each test it has an estimate setup time, calibration time and test execution. Setup could be 1min for a helmet change, like 10min for wrenching. Calibration is tunnel dependant and depends on the change done. Test duration depended on the yaw sweep selected. Right there is a whole discussion. We were probably 45minutes off in an 8 hour session and got all tests done.

I spent 99% of my time in the control room. I would monitor and adjust the schedule. I would feed the results real time into an analysis sheet to make sure they made sense. I would monitor the position of the rider to make sure the test was as planned. There is nothing worst then getting home and go “wonder what happened”. Often you “build” upon the best previous test. Better hope “best” was actually best or all your results are compromised

Maybe 5% of the tests didn’t make sense but had we not caught it on the fly, the session would have been awful. Of course you can mitigate things doing A,B, C, repeat B, repeat A…but that gets expensive

The run sheet was optimised and was driven by importance of tests

Brian makes a pitch for outdoor testing and he is right. A plan to “get aero” that does not have a road testing component is flawed IMO. We made sure results from the tunnel panned out in the real world. We now do road, road, tunnel, road, road. We continuously iterate. You can do the “one and done” approach. My bet is you will get 25% of the benefit. I heard you on a podcast (very good BTW) and I wouldn’t form an opinion with self use of a home device now 8 years old (the tech has moved on)

I could write 10 pages on this and the results we found. But my conclusion is get a set of knowledgeable eyeballs (like Brian). Msg me if you want any details, I am always willing to help.

If you want to fly to Girona in Dec, I’ll test you on the road. Cost : 2 beers