Some random wind tunnel observations and datapoints

Mar 14, 17 18:03

Post #1 of 46 Views: 6489

Thanks to the folks at Faster, I got a few insights on positioning and gear. A few big lessons (which may or may not apply to anyone else):

1) My seat was too low. I guess I should have listened to Dan Empfield. Maybe some of you remember this thread:

Slowman says Jens' seat is too LOW...

In the intervening decade, I reverted to my old, bad ways and lowered it again. Aaron suggested raising it 2 cm. Hmm. Same as Dan.

2) More drop isn't always better. How your body achieves that drop matters. I went from ~14cm drop to ~10 and ended up with less drag. That's really big, because for me, 4cm less drop also means ~15 watts more power output.

3) Helmets really, really matter. In my case, the difference between two aero helmets was over 100 grams of drag.

4) Skinsuit matters. A slightly baggy one vs. better fitting swiftspin was worth around 70 grams.

5) Q-factor matters, though not as much as hoped. I switched from ~160 to ~130, which saved ~50 grams at 0 deg; 34 grams at 5 deg; but actually increased drag 19 grams at 10 deg. Maybe some smarter folks than myself can interpret that.

My latest book: "Out of the Melting Pot, Into the Fire" is on sale on Amazon and at other online and local booksellers

Last edited by: jens: Mar 15, 17 9:12

Re: Some random wind tunnel observations and datapoints [jens] [ In reply to ]

Mar 14, 17 18:22

Post #2 of 46 Views: 6466

Jens, Thank you for posting this. I really enjoy your posts and have gotten a lot out of them. Much appreciated.

Re: Some random wind tunnel observations and datapoints [jens] [ In reply to ]

Mar 14, 17 19:22

Post #3 of 46 Views: 6415

jens wrote:

Thanks to the folks at Faster, I got a few insights on positioning and gear. A few big lessons (which may or may not apply to anyone else):

1) My seat was too low. I guess I should have listened to Dan Empfield. Maybe some of you remember this thread:

Slowman says Jens' seat is too LOW...

In the intervening decade, I reverted to my old, bad ways and lowered it again. Aaron suggested raising it 2 cm. Hmm. Same as Dan.

2) More drop isn't always better. How your body achieves that drop matters. I went from ~14cm drop to ~10 and ended up with less drag. That's really big, because for me, 4cm less drop also means ~15 watts more power output.

3) Helmets really, really matter. In my case, the difference between two aero helmets was over 100 grams of drag.

4) Skinsuit matters. A slightly baggy one vs. better fitting swiftspin was worth around 70 grams.

5) Q-factor matters, though not as much as hoped. I switched from ~160 to ~130, which saved ~50 grams at 0 deg; 34 grams at 5 deg; but actually increased drag 19 grams at 10 deg. Maybe some smarter folks than myself can interpret that.

One thing I'm starting to appreciate is just how individual aerodynamics is. For me, the delta between my slowest helmet and my fastest helmet was 27 grams and the majority of my helmets were within 10 grams of each other. My Virklon sleeved tri suit was actually *slower* than my sleeveless Kiwami tri suit by 25 grams. Sorcery I tell you!

Just a random thought, the people at Faster, A2, etc. should consider tracking body morphology to see if there are any trends.

Re: Some random wind tunnel observations and datapoints [jens] [ In reply to ]

Mar 14, 17 20:51

Post #4 of 46 Views: 6362

Great post, thanks for sharing! Can you expand on the aero helmet testing? Did you test head down and head up positions? Did you only test two helmets, or was that the delta between best and worst?

Also, I'm curious how they determine increased power output from positional changes. Do you just do a max effort in each position?

Re: Some random wind tunnel observations and datapoints [chrisgrigsby] [ In reply to ]

Mar 14, 17 21:38

Post #5 of 46 Views: 6326

chrisgrigsby wrote:

Great post, thanks for sharing! Can you expand on the aero helmet testing? Did you test head down and head up positions? Did you only test two helmets, or was that the delta between best and worst?

Also, I'm curious how they determine increased power output from positional changes. Do you just do a max effort in each position?

I only tested two helmets and just in the position I would actually ride in -- low, but eyes up the road. I suspect helmets are highly individual. I previously compared notes with an Olympian who had tested the same two helmets as me and had precisely the opposite results(!).

The drop/power differences are based on my own long-term experience. I'm probably an an extreme example in this regard. Even with the clown cranks, going from a road position to 14cm drop decreases power over 30 watts.

My latest book: "Out of the Melting Pot, Into the Fire" is on sale on Amazon and at other online and local booksellers

Re: Some random wind tunnel observations and datapoints [GreenPlease] [ In reply to ]

Mar 14, 17 22:26

Post #6 of 46 Views: 6299

The problem with body morphology is that it's hard to categorize, because numbers alone wouldn't do; it'd be more about proportions and shape. I seem to recall Steve Hed (or maybe Cobb, crap I'm getting older) hypothesizing once that high hands worked better depending on the riders hips size.

Re: Some random wind tunnel observations and datapoints [jens] [ In reply to ]

Mar 14, 17 22:44

Post #7 of 46 Views: 6289

jens wrote:

Thanks to the folks at Faster, I got a few insights on positioning and gear. A few big lessons (which may or may not apply to anyone else):

1) My seat was too low. I guess I should have listened to Dan Empfield. Maybe some of you remember this thread:

Slowman says Jens' seat is too LOW...

In the intervening decade, I reverted to my old, bad ways and lowered it again. Aaron suggested raising it 2 cm. Hmm. Same as Dan.

2) More drop isn't always better. How your body achieves that drop matters. I went from ~14cm drop to ~10 and ended up with less drag. That's really big, because for me, 4cm less drop also means ~15 watts more power output.

3) Helmets really, really matter. In my case, the difference between two aero helmets was over 100 grams of drag.

4) Skinsuit matters. A slightly baggy one vs. better fitting swiftspin was worth around 70 grams.

5) Q-factor matters, though not as much as hoped. I switched from ~160 to ~130, which saved ~50 grams at 0 deg; 34 grams at 5 deg; but actually increased drag 19 grams at 10 deg. Maybe some smarter folks than myself can interpret that.

Cool.
But you had something janky in the link to the old 2007 thread, so I took the liberty of posting it below. It's too good of a thread for folks to not be able to just click :-)
http://forum.slowtwitch.com/forum/?post=1324075

http://bikeblather.blogspot.com/

Re: Some random wind tunnel observations and datapoints [jens] [ In reply to ]

Mar 15, 17 2:42

Post #8 of 46 Views: 6206

Thanks for sharing... nice insights.

"Too Low/High" is always possible... it all depends on what point you are referencing as the "start"

I found my saddle could be raised 1cm with no effect on aerodynamics, but some relief in the hip angle. Front end was the same... dropping 20mm of spacers was almost the same as higher, dropping 40mm of spacers was worse than higher. Like all things aerodynamics... it depends.

Helmets only mattered a bit (comparing only the ones I would have guessed were fast) but skinsuits mattered a lot, even among some of the faster (or so I thought) TT options.

My Blog - http://leegoocrap.blogspot.com

Re: Some random wind tunnel observations and datapoints [jens] [ In reply to ]

Mar 15, 17 3:17

Post #9 of 46 Views: 6188

jens wrote:

Thanks to the folks at Faster, I got a few insights on positioning and gear. A few big lessons (which may or may not apply to anyone else):

1) My seat was too low. I guess I should have listened to Dan Empfield. Maybe some of you remember this thread:

Slowman says Jens' seat is too LOW...

In the intervening decade, I reverted to my old, bad ways and lowered it again. Aaron suggested raising it 2 cm. Hmm. Same as Dan.

Did you test different saddle heights in the wind tunnel?

Re: Some random wind tunnel observations and datapoints [Andrew Coggan] [ In reply to ]

Mar 15, 17 5:26

Post #10 of 46 Views: 6107

that's what I want to know too +1

when I did, lower saddle was much faster

Re: Some random wind tunnel observations and datapoints [jens] [ In reply to ]

Mar 15, 17 7:14

Post #11 of 46 Views: 6007

How many grams of drag did you have total? I'm curious what 100 grams of drag difference in helmets works out to be percentage-wise.

How many runs did you do total?

How much less drag did you have at 10cm of drop versus 14cm?

Regarding the increase in drag at 10 degrees of yaw on the Q-Factor change, did that increase occur at 10 degrees both left and right? Is it different drive-side versus non-drive-side?

Travis Rassat
Vector Cycle Works
Noblesville, IN
BikeFit Instructor | FMS | F.I.S.T. | IBFI
Toughman Triathlon Series Ambassador

Re: Some random wind tunnel observations and datapoints [Andrew Coggan] [ In reply to ]

Mar 15, 17 9:07

Post #12 of 46 Views: 5944

Andrew Coggan wrote:

Did you test different saddle heights in the wind tunnel?

Not in isolation. We raised the saddle by 2cm and bars by ~6cm at the same time. We made the latter change by switching from FSA Vision bars to 3T Aura Pros and adding a bunch of risers. Average drag was slightly (30grams) lower.

So no apples to apples --or even fruit to fruit-- comparison. More like fruit to vegetable. ;-)

My latest book: "Out of the Melting Pot, Into the Fire" is on sale on Amazon and at other online and local booksellers

Last edited by: jens: Mar 15, 17 9:34

Re: Some random wind tunnel observations and datapoints [jens] [ In reply to ]

Mar 15, 17 9:40

Post #13 of 46 Views: 5903

jens wrote:

Andrew Coggan wrote:

Did you test different saddle heights in the wind tunnel?

Not in isolation. We raised the saddle by 2cm and bars by ~6cm at the same time. We made the latter change by switching from FSA Vision bars to 3T Aura Pros and adding a bunch of risers. Average drag was slightly (30grams) lower.

So no apples to apples --or even fruit to fruit-- comparison. More like fruit to vegetable. ;-)

So you don't know if raising your saddle hurt your aerodynamics. Do you know if it increased your power?

Re: Some random wind tunnel observations and datapoints [jens] [ In reply to ]

Mar 15, 17 9:41

Post #14 of 46 Views: 5899

did you test the aura at the baseline as well or just completely wholesale nothing to compare swap?

Re: Some random wind tunnel observations and datapoints [jens] [ In reply to ]

Mar 15, 17 10:03

Post #15 of 46 Views: 5882

Interesting results. Thanks for sharing. I wanted to add a couple points from my two trips to Faster with Ventum over the past two years.

jens wrote:

2) More drop isn't always better. How your body achieves that drop matters. I went from ~14cm drop to ~10 and ended up with less drag. That's really big, because for me, 4cm less drop also means ~15 watts more power output.

This was my experience as well. Raising my pads 1 cm lowered drag. It also felt significantly more comfortable and powerful. This small change allowed me to shrug my shoulders and turtle my head more naturally.

jens wrote:

4) Skinsuit matters. A slightly baggy one vs. better fitting swiftspin was worth around 70 grams.

My most surprising result was that my Kiwami ITU suit tested about the same or significantly faster than two sleeved suits. Neither fit really well and both had wrinkles in the shoulder area, which may explain the poor results. I'll be sticking with ITU suits until I can show that the benefits of sleeves outweigh the disadvantages for me (heat, effect on swim, slower T1...).

CodyBeals.com | Instagram | TikTok
ASICS | Ventum | Martin's | HED | VARLO | Shimano | 4iiii | Keystone Communications

Re: Some random wind tunnel observations and datapoints [Cody Beals] [ In reply to ]

Mar 15, 17 10:14

Post #16 of 46 Views: 5856

Cody Beals wrote:

Interesting results. Thanks for sharing. I wanted to add a couple points from my two trips to Faster with Ventum over the past two years.

jens wrote:

4) Skinsuit matters. A slightly baggy one vs. better fitting swiftspin was worth around 70 grams.

My most surprising result was that my Kiwami ITU suit tested about the same or significantly faster than two sleeved suits. Neither fit really well and both had wrinkles in the shoulder area, which may explain the poor results. I'll be sticking with ITU suits until I can show that the benefits of sleeves outweigh the disadvantages for me (heat, effect on swim, slower T1...).

I had the same thing happen with my Kiwami ITU suit except my sleeved kits actually fit really well with practically no wrinkles.

Re: Some random wind tunnel observations and datapoints [Andrew Coggan] [ In reply to ]

Mar 15, 17 15:12

Post #17 of 46 Views: 5736

Andrew Coggan wrote:

So you don't know if raising your saddle hurt your aerodynamics. Do you know if it increased your power?

Since we tested "the whole system" rather than that specific measure, there's no way to say what raising the saddle by itself did. Power is definitely higher. But even that is reflective of a whole system change (i.e. less drop). Maybe in a week, I'll try dropping both the bars and the saddle back down 2cm and do a few power tests.

My latest book: "Out of the Melting Pot, Into the Fire" is on sale on Amazon and at other online and local booksellers

Re: Some random wind tunnel observations and datapoints [Cody Beals] [ In reply to ]

Mar 16, 17 11:09

Post #18 of 46 Views: 5542

If you haven't read Cody's wind tunnel article it's a great read. I frequently find myself going back to it for reference.

Cody Beals wrote:

Interesting results. Thanks for sharing. I wanted to add a couple points from my two trips to Faster with Ventum over the past two years.

jens wrote:

2) More drop isn't always better. How your body achieves that drop matters. I went from ~14cm drop to ~10 and ended up with less drag. That's really big, because for me, 4cm less drop also means ~15 watts more power output.

This was my experience as well. Raising my pads 1 cm lowered drag. It also felt significantly more comfortable and powerful. This small change allowed me to shrug my shoulders and turtle my head more naturally.

jens wrote:

4) Skinsuit matters. A slightly baggy one vs. better fitting swiftspin was worth around 70 grams.

My most surprising result was that my Kiwami ITU suit tested about the same or significantly faster than two sleeved suits. Neither fit really well and both had wrinkles in the shoulder area, which may explain the poor results. I'll be sticking with ITU suits until I can show that the benefits of sleeves outweigh the disadvantages for me (heat, effect on swim, slower T1...).

Re: Some random wind tunnel observations and datapoints [Cody Beals] [ In reply to ]

Mar 16, 17 14:13

Post #19 of 46 Views: 5462

regarding aero suits, how far and what would your limit on budget be to get two suits made custom to you, measured to your body in your chosen position on the bike?

Anne Barnes
ABBikefit, Ltd
FIST/SICI/FIST DOWN DEEP
X/Y Coordinator
abbikefit@gmail.com

Re: Some random wind tunnel observations and datapoints [ABarnes] [ In reply to ]

Mar 16, 17 14:36

Post #20 of 46 Views: 5435

ABarnes wrote:

regarding aero suits, how far and what would your limit on budget be to get two suits made custom to you, measured to your body in your chosen position on the bike?

It depends

Re: Some random wind tunnel observations and datapoints [James Haycraft] [ In reply to ]

Mar 16, 17 14:39

Post #21 of 46 Views: 5432

haha, excellent response.
ok, more exact question: if I was a BioRacer Speedsuit provider, would you come to chicago to get it fitted? two suits, with or without longsleeves, plus a little bit of time with me for about $2k.

Chicago is really nice this time of year. :)

Anne Barnes
ABBikefit, Ltd
FIST/SICI/FIST DOWN DEEP
X/Y Coordinator
abbikefit@gmail.com

Re: Some random wind tunnel observations and datapoints [ABarnes] [ In reply to ]

Mar 16, 17 14:40

Post #22 of 46 Views: 5429

It's more a $/watt question. If this custom designed GUARANTEED watt savings at the rate of say...$100/3-5w then I might consider it.

Re: Some random wind tunnel observations and datapoints [jens] [ In reply to ]

Mar 17, 17 0:12

Post #23 of 46 Views: 5310

Thanks for sharing.

I wonder if people ever measured the drag of a racenumber with a belt which you have to wear at nearly every triathlon. Whether that deletes the advantage of a suit over two-part wear for example.
Related to that: I watched the WC Kona carefully again on youtube, but I didn't see any belts with numbers, also not with the AG, am I blind or do you not have to wear a number on the bike in Kona?

Re: Some random wind tunnel observations and datapoints [longtrousers] [ In reply to ]

Mar 17, 17 0:21

Post #24 of 46 Views: 5304

You don't have to wear it in most IM races in North America.
Other parts of the world I am not sure. For example I think France requires it

Re: Some random wind tunnel observations and datapoints [longtrousers] [ In reply to ]

Mar 17, 17 3:30

Post #25 of 46 Views: 5256

longtrousers wrote:

Thanks for sharing.

I wonder if people ever measured the drag of a racenumber with a belt which you have to wear at nearly every triathlon. Whether that deletes the advantage of a suit over two-part wear for example.
Related to that: I watched the WC Kona carefully again on youtube, but I didn't see any belts with numbers, also not with the AG, am I blind or do you not have to wear a number on the bike in Kona?

Many years ago I tested race number position (belt) on my tri bike at a2, there was a 5 watts difference between low on my back and high (like a hr strap high) on my bike) and about 8w difference wearing it on my front (low back was best)

Wearing on a 2pc tri kit was worse than on a one piece (an old LG two piece and a 1 pc Desoto, both 2010'ish neither with any kind of sleeves)

Draw from that whatever (if anything) you would.

My Blog - http://leegoocrap.blogspot.com

Re: Some random wind tunnel observations and datapoints [longtrousers] [ In reply to ]

Mar 17, 17 5:38

Post #26 of 46 Views: 4114

If my memory is correct, Jordan Rapp tested this at Specialized and didn't see a difference whereas the NoPinz guys tested their number pocket against a belt and found a savings of 3-5 watts.

Re: Some random wind tunnel observations and datapoints [leegoocrap] [ In reply to ]

Mar 17, 17 5:54

Post #27 of 46 Views: 4103

has anybody tested the affect of stuff in back pockets? My nutrition plan for half's on my new bike is an EFS liquid shot in each of the two pockets on the castelli T1. Trying to keep the bike clean and hoped this wouldn't add much drag.

Re: Some random wind tunnel observations and datapoints [longtrousers] [ In reply to ]

Mar 17, 17 7:10

Post #28 of 46 Views: 4081

longtrousers wrote:

Thanks for sharing.

I wonder if people ever measured the drag of a racenumber with a belt which you have to wear at nearly every triathlon. Whether that deletes the advantage of a suit over two-part wear for example.
Related to that: I watched the WC Kona carefully again on youtube, but I didn't see any belts with numbers, also not with the AG, am I blind or do you not have to wear a number on the bike in Kona?

For short course racing here in NA, the only race I've ever "had" to wear my number belt on the bike was ITU Chicago.

Re: Some random wind tunnel observations and datapoints [Sean H] [ In reply to ]

Mar 17, 17 7:44

Post #29 of 46 Views: 4068

Never tested it, but low back *can be a sensitive area... If there was a clean option elsewhere I would move it there to be safe

My Blog - http://leegoocrap.blogspot.com

Re: Some random wind tunnel observations and datapoints [leegoocrap] [ In reply to ]

Mar 17, 17 7:55

Post #30 of 46 Views: 4058

leegoocrap wrote:

Never tested it, but low back *can be a sensitive area... If there was a clean option elsewhere I would move it there to be safe

I take some credit for popularizing this a while back:

http://www.3m.com/3M/en_US/company-us/all-3m-products/~/3M-Super-77-Multi-Purpose-Adhesive?N=5002385+3294224953+4294924301&rt=rud

Works great for OBRA bibs. I don't know if it works with triathlon numbers though.

My latest book: "Out of the Melting Pot, Into the Fire" is on sale on Amazon and at other online and local booksellers

Last edited by: jens: Mar 17, 17 7:57

Re: Some random wind tunnel observations and datapoints [jens] [ In reply to ]

Mar 17, 17 8:00

Post #31 of 46 Views: 4050

jens wrote:

leegoocrap wrote:

Works great for OBRA bibs. I don't know if it works with triathlon numbers though.

Works with everything I've ever tried it on, e.g. paper-based or nylon-based numbers

Re: Some random wind tunnel observations and datapoints [jens] [ In reply to ]

Mar 17, 17 8:07

Post #32 of 46 Views: 4047

I'm interested to see a picture of you 3m adhesiving what you keep in your back pockets... ;) I assume he was talking about nutrition

My Blog - http://leegoocrap.blogspot.com

Re: Some random wind tunnel observations and datapoints [jens] [ In reply to ]

Mar 17, 17 10:17

Post #33 of 46 Views: 4000

jens wrote:

Andrew Coggan wrote:

Did you test different saddle heights in the wind tunnel?

Not in isolation. We raised the saddle by 2cm and bars by ~6cm at the same time. We made the latter change by switching from FSA Vision bars to 3T Aura Pros and adding a bunch of risers. Average drag was slightly (30grams) lower.

So no apples to apples --or even fruit to fruit-- comparison. More like fruit to vegetable. ;-)

I've never tested anyone where raising bars and seat together (the same amount) wasn't slower, so call me suspicious of that as a "finding". Still, it seems the package of changes was good for you so that's great news.

Thanks for sharing. It sounds like you were happy with Faster?

Re: Some random wind tunnel observations and datapoints [James Haycraft] [ In reply to ]

Mar 17, 17 10:20

Post #34 of 46 Views: 3994

Thank you. That is good info.

Castelli claims their speedsuit "saves 10-15w at 25mph". The cop out is always "your results may vary".
Difficult to find test data with brand names etc, although there is a fair amount of this study on just fabrics.

BioRacer at least addresses fit issues, esp at the armpits, or at the neck as it is tailored to the individual.
Lexxi suits are also same price range with tailoring and paneling of specific fabrics.

In god we trust, all others bring data.

Anne Barnes
ABBikefit, Ltd
FIST/SICI/FIST DOWN DEEP
X/Y Coordinator
abbikefit@gmail.com

Re: Some random wind tunnel observations and datapoints [ABarnes] [ In reply to ]

Mar 17, 17 10:25

Post #35 of 46 Views: 3990

ABarnes wrote:

Thank you. That is good info.

Castelli claims their speedsuit "saves 10-15w at 25mph". The cop out is always "your results may vary".
Difficult to find test data with brand names etc, although there is a fair amount of this study on just fabrics.

BioRacer at least addresses fit issues, esp at the armpits, or at the neck as it is tailored to the individual.
Lexxi suits are also same price range with tailoring and paneling of specific fabrics.

In god we trust, all others bring data.

Interestingly, the delta between my two piece tri kit (B70 TX2000) and my Castelli BP3 TT skinsuit was ~.004 Cda. So yea, notttt quite "10-15w."

And that skinsuit fits real good.

Re: Some random wind tunnel observations and datapoints [ABarnes] [ In reply to ]

Mar 17, 17 12:48

Post #36 of 46 Views: 3956

ABarnes wrote:

Castelli claims their speedsuit "saves 10-15w at 25mph". The cop out is always "your results may vary".
Difficult to find test data with brand names etc, although there is a fair amount of this study on just fabrics.

BioRacer at least addresses fit issues, esp at the armpits, or at the neck as it is tailored to the individual.
Lexxi suits are also same price range with tailoring and paneling of specific fabrics.

Personally I think the tailored option is the way to go albeit incredibly expensive. If you want some more data I tested 4 kits. 2xu sleeveles skit, 2xu sleeved kit, and two different sized Coure kits. All data here:

Save: $50 on Speed Hound Recovery Boots | $20 on Air Relax| $100 on Normatec| 15% on Most Absorbable Magnesium

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Last edited by: Thomas Gerlach: Mar 17, 17 13:58

Re: Some random wind tunnel observations and datapoints [EnderWiggan] [ In reply to ]

Mar 17, 17 12:50

Post #37 of 46 Views: 3952

EnderWiggan wrote:

If you haven't read Cody's wind tunnel article it's a great read. I frequently find myself going back to it for reference.

Give me some feedback. How can I adjust my own writing to get your recommendation. Fwiw, I am in the process of writing up another athletes results so I will think about your criticism and try to address in my next version.

Save: $50 on Speed Hound Recovery Boots | $20 on Air Relax| $100 on Normatec| 15% on Most Absorbable Magnesium

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Re: Some random wind tunnel observations and datapoints [Thomas Gerlach] [ In reply to ]

Mar 17, 17 13:55

Post #38 of 46 Views: 3907

awesome.
Link is broken?

Anne Barnes
ABBikefit, Ltd
FIST/SICI/FIST DOWN DEEP
X/Y Coordinator
abbikefit@gmail.com

Re: Some random wind tunnel observations and datapoints [ABarnes] [ In reply to ]

Mar 17, 17 13:57

Post #39 of 46 Views: 3905

Somehow extra http: got added to the end, sorry about that. Try this

Save: $50 on Speed Hound Recovery Boots | $20 on Air Relax| $100 on Normatec| 15% on Most Absorbable Magnesium

Blogs: Best CHEAP Zwift / Bike Trainer Desk | Theragun G3 vs $140 Bivi Percussive Massager | Normatec Pulse 2.0 vs Normatec Pulse | Speed Hound vs Normatec | Air Relax vs Normatec | Q1 2018 Blood Test Results | | Why HED JET+ Is The BEST value wheelset

Last edited by: Thomas Gerlach: Mar 17, 17 13:58

Re: Some random wind tunnel observations and datapoints [jens] [ In reply to ]

Mar 17, 17 17:41

Post #40 of 46 Views: 3831

jens wrote:

2) More drop isn't always better. How your body achieves that drop matters. I went from ~14cm drop to ~10 and ended up with less drag. That's really big, because for me, 4cm less drop also means ~15 watts more power output.

Good stuff, Jens!

For sure, effective reach can be impacted by how low one chooses to have their bars. However, if one maintains their effective reach while changing drop, the average change in cxa is about 1% per cm. For reach, it's about 1% change in cxa per 2cm. Tippin' it can be a bummer (y axis is axial force in the image below):

Quote:

3) Helmets really, really matter. In my case, the difference between two aero helmets was over 100 grams of drag.

I don't know what speed your were running at, but here's an early sampling from my database of the delta between a vented road helmet and an aero helmet:

http://www.biketechreview.com/...49-aero-helmets-work

IME, a good head position is pretty robust to helmet choice. Some thoughts on head position here:

=================
Kraig Willett
http://www.biketechreview.com - check out our reduced report pricing
=================

Re: Some random wind tunnel observations and datapoints [leegoocrap] [ In reply to ]

Mar 19, 17 6:38

Post #41 of 46 Views: 3687

leegoocrap wrote:

longtrousers wrote:

Thanks for sharing.

I wonder if people ever measured the drag of a racenumber with a belt which you have to wear at nearly every triathlon. Whether that deletes the advantage of a suit over two-part wear for example.
Related to that: I watched the WC Kona carefully again on youtube, but I didn't see any belts with numbers, also not with the AG, am I blind or do you not have to wear a number on the bike in Kona?

Many years ago I tested race number position (belt) on my tri bike at a2, there was a 5 watts difference between low on my back and high (like a hr strap high) on my bike) and about 8w difference wearing it on my front (low back was best)

Wearing on a 2pc tri kit was worse than on a one piece (an old LG two piece and a 1 pc Desoto, both 2010'ish neither with any kind of sleeves)

Draw from that whatever (if anything) you would.

Thank you. Wow, a lot of difference for such a belt. Probably the difference of wearing one or not will then also be at least 5w.

Interesting that in America you normally do not wear a bodynumber on the bike. Here in Europe my only experience is that you have to.

Re: Some random wind tunnel observations and datapoints [Thomas Gerlach] [ In reply to ]

Mar 20, 17 10:45

Post #42 of 46 Views: 3562

wonderful writeup, and great blog.
favoriting, following and cheering you on.

Anne Barnes
ABBikefit, Ltd
FIST/SICI/FIST DOWN DEEP
X/Y Coordinator
abbikefit@gmail.com

Re: Some random wind tunnel observations and datapoints [jkhayc] [ In reply to ]

May 25, 17 10:32

Post #43 of 46 Views: 3259

It's about 15-20 watts compared to the next best suit.
$1850 for 2 suits like Ann said.
+ free shoe covers and gloves

Re: Some random wind tunnel observations and datapoints [jens] [ In reply to ]

May 25, 17 10:54

Post #44 of 46 Views: 3243

"The drop/power differences are based on my own long-term experience. I'm probably an an extreme example in this regard. Even with the clown cranks, going from a road position to 14cm drop decreases power over 30 watts.

What is your drop in your road position?

Re: Some random wind tunnel observations and datapoints [AG] [ In reply to ]

May 26, 17 7:34

Post #45 of 46 Views: 3124

0. Although the comparison is not particularly meaningful since "drop to elbow pads" and "drop to brakehoods" are two completely different things.

My latest book: "Out of the Melting Pot, Into the Fire" is on sale on Amazon and at other online and local booksellers

Re: Some random wind tunnel observations and datapoints [jens] [ In reply to ]

May 28, 17 0:28

Post #46 of 46 Views: 3000

0. Although the comparison is not particularly meaningful since "drop to elbow pads" and "drop to brakehoods" are two completely different things.

Your road position drop (saddle to hoods) is zero? As in there is no drop? Weird that's almost a bike packing / touring setup. I'm trying to understand how you can lose 30 watts. It would seem that you would need some serious torso to thigh angle compression to lose that much power. At 14cm TT drop I don't get it.

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