I have loosely made this argument for years to many when it comes to equipment choices, especially when they are selecting something that is a few grams lighter. I'll be following and interested to see what exactly happens here. Losing 40-50lbs in the name of science sounds like a fantastic carrot to get fit and be healthier.

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Curious if changes in position are allowed. Seems like losing significant weight around the gut would allow you to get into a different position?

Thanks, Thomas. Yeah, I've been needing to get my arse in shape for quite some time, and had also been wanting to do this type of testing, so two birds...

I really have no idea how this will work out. I know it'll make a difference, but I'm not sure how much. It's really about losing size as I lose weight. I'm already quite a bit smaller than the original video, so I'll test again hopefully this coming week or early next. I was supposed to test Saturday, but we went long and ran out of time.

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Jim Manton / ERO Sports

When all my weight is lost, we'll change position for sure because you're correct, I'll be capable of better. But for now, I just want it to be about losing size. Smaller area = lower drag.

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Jim Manton / ERO Sports

Awesome thread. Looking forward to the science and good on you for the commitment to yourself!

 I think it's going to be very difficult to isolate the actual reduction in drag due to body area reduction, since it'll be conflated with both clothing changes and position changes. All the skinsuits and aero jerseys are not exactly able to fit a beer belly, and holding an aero tuck without losing power with said gut is also rather challenging.

Both clothing and position were addressed in the video. Position will not change. I've started with a XXL LG Tri Suit, but also have an XL and L I'll change to for better fit. In fact, for my next test, I'll already need to size down to the XL. I have no trouble holding the position and power. It's rather pedestrian for me as historically my aero bar is several cm lower. However, I'm purposely not riding in this position during this period of testing because one thing we do know is the more accustomed to a position you become, the lower your drag will be. The only time I'm riding in aero right now is when I'm testing.

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Jim Manton / ERO Sports

Thanks! This should be fun, and it's a great way to learn something while bettering my health.

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Jim Manton / ERO Sports

It matters. Think about how nice it is to be 2nd wheel in a fast group ride behind a big guy versus a girl!

That's just mass/size also. That doesn't address what positions are possible on the bike. The bigger you are the less aggressive you'll probably be able to be.

The rest of this is just babble:


It's childish, but this is a beef I have with Zwift racing for time trials. Ain't no way in hell people that big as some are can be able to hold the same aero position. They'd need a weight/height based lookup table for CdA adjustment or something.

I do TT's on there with guys who hold the same 4w/kg but are putting out 50 to even 75 more watts because they're the size of a refrigerator. Real life? Yeah, no way in hell they've got that good of a CdA.

Smaller area = lower drag
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I could see a case to be made for a larger body, especially in the middle regions, to allow air to flow more fluidly around the object. The belly fills in the gap between the chest and top tube. There are lots of aquatic mammals that aren't very thin and are quite round that are also efficiently hydrodynamic. Perhaps the same set of rules can apply to a larger human on a bike.

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Take a short break from ST and read my blog:
http://tri-banter.blogspot.com/

Love it, will be following this closely.

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"They're made of latex, not nitroglycerin"

Just wanted to say good luck and I'll be following along - down ~35ish since hip surgery and have wondered about this very thing...

I can't watch the video from work.

Andy Coggan used to make the point that kg was the good surrogate for A.

Really looking forward to this data!
Although I’m pretty lean I have a 42inch chest and alway been curious how much my drag would change if I dropped muscle.

I love it, Jim... this is great!

"A" is one aspect, "Cd" is another. The beer gut is actually aero, so you'll lose some there... ;) Slimmer arms, legs, shoulders(?), and butt should help. My WAG if you drop to 192 lbs, and change nothing but going down in suit size, is a CdA of .285 from .3052.

Can you say more about the aero sensor and what protocol you use?

I'm about 190+, so I'm very interested.

Excellent video - only 79 subscribers, c'mon Slowtwitch!

It is important where the weight is lost!

Have not had a chance to watch just yet Jim but just wondering if you explain how you are managing to lose so much weight? Any secrets?? That amount of weight loss is pretty amazing, I would love to just drop 10-15 pounds let alone 40-50!!

Back in the day when i first did some aero work, we found that some more rotund riders were more aero the larger they were as you describe.

Nonetheless, as Jim is aware, losing weight can have other significant benefits (on health etc)

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http://www.cyclecoach.com

I was thinking I needed to do a whole post/video about the sensor, the protocols, and even some aero basics for those who aren't aware. I assume folks know what CdA means, but I shouldn't. I'll get to work on that next week for sure.

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Jim Manton / ERO Sports

Has anyone actually challenged you on that (ie I won’t be faster/more aero if I’m lighter). I’m curious to see the results but *I think* this would be self evident.

I used to ride w/ a guy who was tiny (actually pretty buff, just really short for a grown-ass dude). Not sure his road frame size, but guessing a 51, and a real compact default road position (he even rode his MTB w/ the stem flipped to negative rise so he could get the front end low enough to not be pulling wheelies all the time). I used to HATE trying to draft off that little fucker ~ i'm not even super tall (6-1 on a 58 frame) but I swear I could still see the pavement only a few feet ahead of him over the top of his head!

Okay, so I know this would be a topic, and possibly a hot one. I've always known I could lose weight very quickly, and honestly used that as an excuse not to lose weight. "I can lose it whenever I want" would be my justification for "I'll start next week."

Though it's quite the fad at the moment, I stumbled upon intermittent fasting a few decades ago. It works well for me and, though many a dietitian will disapprove of me saying this (and they're right), I can be pretty extreme about it and lose 2-3 lbs per day. Now then, I do not condone this for anyone else. It's not the healthiest way to do it by any stretch of the imagination. When I say I'm extreme, I'm basically starving myself and I freely admit it. But, then again, 242 lbs is in no way a natural weight for me, so it's almost as if my body can't wait to shed it as soon as possible. In fact, I really felt like I needed to get this weight off before I experienced a real health problem. I don't know, it's as if my body was begging me to get it done once and for all. I'm not sure how else to explain that, but I felt an urgency to get healthy.

To be transparent with everyone, which I think is important as I do this, my poor diet has resulted in a history of both gout and kidney stones, neither of which are fun, but both completely avoidable...totally on me. I am giving myself breaks from IF to keep sane and, funny enough, though I've already lost 20 lbs, I won't be able to test again until next week, so I need to stop losing weight for now so I can get the drag number! Lol.

I think this could use further discussion, and I know there'll be many questions. I'll answer as much as possible with the time I have.

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Jim Manton / ERO Sports

This is kind of fun (maybe not for you)

I think we should have a Cda betting pool, my pics:

236 at .305
226 at .297
216 at .280
206 at .272
196 at .260
186 at .252

Only changes being suit.

Maurice