FlashBazbo

Last weekend, I did the cycling segment of an area triathlon (relay category). To my surprise, after I had racked my bike, a guy I've ridden with before walked up to his bike which was racked next to mine. I had a pretty good idea he was going to beat me. Although my team won the relay, he beat me by about 5 minutes in the cycling leg. The differences:

I'm a relatively big guy (5'10", 174 lbs) with 46cm WIDE shoulders. I rode my BMC Teammachine road bike with 25mm deep aluminum climbing wheels and no aero bars. Bibs and jersey. No shoe covers. No shaved legs. No coaching. I rode in the drops the whole way.

He is a relatively smaller guy (@5'6", 135 lbs) with 39cm narrow shoulders. He rode a full aero Tri bike with a full disc rear wheel and a 90mm deep front aero wheel. Even taped up the inflator hole in the disc. He wore a skin suit, a TT helmet, and shoe covers. Shaved legs and arms. Lots of coaching on his bike position. He rode on the extensions the whole way. Smoked me.

After the race, we looked at our power data. I figured he must have averaged 70 or 80 more watts than I did. At the end of the day, looking at our respective power files, his average power was higher than mine . . . by just one (1) watt!

Even if you assume a MASSIVE margin for error, I'm going to take this experience as pretty strong evidence that aero really matters . . . a lot. My wide body will never be as aero as his narrow shoulders. He will always be more aero than I am. But equivalent equipment would surely have erased a lot of the difference.

redlude97

he's also putting out way more watts/kg than you too though. On a perfectly flat course overall power is important but with any rollers and especially if you look at power on those hills that might play a significant role as well.

FlashBazbo

Generally, a good point. On this course, though, we just had five sharp, steep rises each of less than 250 feet in length (on our way to and from the main route). The remainder of the course was a very flat out-and-back. Unless you consider a 1% rise and fall to be a roller, we didn't have any rollers. For that reason, we felt the weight difference was pretty irrelevant. Not COMPLETELY irrelevant, but not a huge factor.

Wind direction was huge, though. I kept the two professionals within probably 1/4 mile as we rode outbound (downwind). But when we turned into the wind, they left me in the dust.

redlude97

didnt mean to imply it was the only reason, you're right aero is important and even if you had the same shoulder widths an aero bar position moves so much frontal area out of the wind compared to the drops already, even if you ignore everything else. Have you tried an IAB position?

FlashBazbo

Only briefly, and not in a race. I would need to practice with it. But I ordered a TT/Tri bike last week and it should arrive this week or next. I got tired of being passed by guys on aero bikes who are slower than me on a road bike. Best of all, my WIFE was the first to ask, "Why don't you have one of those bikes?"

redlude97

haha for sure you can buy speed with a TT position over a road position

FlashBazbo

But there IS one other consideration. I know this guy's power files from road rides. On a road bike, he's capable of putting out a lot more watts. I suspect his power was diminished somewhat due to his aero positioning.

I wonder how much power I might lose. I guess we will find out.

redlude97

generally you sacrifice some power but still gain speed. A good fit should optimize both for your body/fitness

treebound 

What bike did you order? Just curious.

Heathpack 

As I said in your other thread about tri bikes, *position* is the most important factor determining aerodynamics. It's significantly more important than equipment. Funny, your post here is like you never even read my response, or perhaps you didn't understand it or fully absorb it.

The guy is faster than you because he's more aero. His equipment matters but his position matters most. It's not just a matter of you going out and buying more aero equipment, it's a matter of being able to ride it in the most effective position.

As to the comment about speed being a matter on power to weight ratio, on a flat TT course this is not correct. It's power to CdA ratio.

I also frequently read here on BF that you lose power in an aero position. Not necessarily true. It takes a lot of adaptation, time riding threshold efforts in position, but the goal is to not have any difference between your power on the road & TT bikes. Not a pipe dream, it's just a lot of work that many people don't want to put in.

That said, if you race TTs and can get yourself into some kind of very fast aero position, something that is substantially faster but you couldn't put out the same power as the road bike- well then screw the power, a race is a contest of speed not power.

The other thing to recognize is that riding perfectly, managing your effort relative to wind, undulations in road, etc, is hugely important. All other things being equal, i.e. two people racing with identical power to CdA, the person who races perfect splits can be surprisingly faster, it could be as much as 15-30 seconds on a 20k TT, just by parcelling your effort out perfectly.

StephenH

Was he doing the full triathlon, or also just doing the bike portion? If a guy's coming out of one event, and planning on going to another, his pacing is bound to be a little different from somebody that afford to go all out on the cycling portion.


On how much the aero matters, a lot of things don't matter much in a lot of circumstances, and you can pay a $1,000 extra and pick up 30 seconds over 40 miles or something. On the other hand, competition with people of similar abilities is the one place where 30 seconds WILL make a difference, so there you go.


I rented a tribike for a weekend last year. Yes I was faster on it. I had problems holding my head at the proper angle, though. I'm assuming working on my positioning and technique would help there, but it's not an instant solution for everything, either.

ZIPP2001

I've competed in well over 200 TT events over the 15 years that I raced back in the day. From TT's a part of a stage race to weekly club TT's, so when seconds or tenths and hundreds of seconds matter between a podium or even a top ten or twenty spot aero can make a difference.

FlashBazbo

Relax. I didn't make a big deal of your previous post because it was self-evident. It's something every knowledgeable racer already knows. Were you hoping for an argument?

Heathpack 

Nope, not looking for an argument. You seem to want to discuss aero-ness. I also like to discuss aero-ness and there is a lot I've learned and am still learning about the process. I'd love to post here about it and actually have a conversation with someone about it.

I have tried to make the point twice now that its not the equipment for the most part (although equipment certainly does matter), but position that is of primary concern.


Yet you conclude your post with the comment: "But equivalent equipment would surely have erased a lot of the difference." You can buy a tri bike and plunk yourself down on it and be slow. I know because people show up to TTs on Tri bikes all the time and are slow.


Whatever, figure it out or don't. I'm out of your conversation. Enjoy your journey.

FlashBazbo

Okay. Okay. I will say what, to this point, has been unsaid. I didn't think it needed to be said.

Given two people of equivalent stature, the MOST important factor in aerodynamics on a bike is body position. BUT . . . having the right equipment (aero bars, TT bike, recumbent, etc.) will allow a person to get into a vastly better aerodynamic body position than a conventional racing bike can. Hence, the discussion about equipment. Equipment enables body position.

But again, as I related, when my shoulders are 7cm wider than my friend's . . . with equivalent positioning . . . nothing's going to overcome that difference short of amputation. (I'm just not that committed.)

FlashBazbo

It's a BMC TimeMachine 02. I've got maybe 100 miles on it now and I'm very impressed with the difference it makes. At this point, I'm a little faster, on average, in high Zone 2 power than I am on my road bike (in the drops) in mid Zone 4. Once I've got my positioning dialed in, I expect both to get my power up and to improve my aerodynamics. Over time, I think a 2 or 3 mph difference might be possible. We will see. This is going to be an interesting off-season project.

gsa103

Yes, but in general bigger riders have an advantage in time trials. If you look at the top time trialists they are all larger riders, the ultra-light climbers get smoked in time trials. It's power/CdA that matters. A rider who is 20% heavier, might only have 5% higher CdA, while making the same W/kg.

If your average power was the same as his, and he's significantly lighter, he's just in much better shape than you are.

FlashBazbo

I'll disagree about a couple things and on one thing I'll agree. (1) Bigger riders don't generally have an advantage in time trials that traces to their size. The bigness or smallness of the rider doesn't matter (apart from the drag surface area). It's the POWER that makes the difference. And bigger riders often produce more power. (2) It's not the Coefficient of Drag that matters when the surface area is so much different. In over-simplified terms, total drag is the real key and total drag is coefficient of drag times surface area. Even if our Coefficients of Drag were equal, the fact that my surface area is so much larger would still make me a lot harder to push through the air. Indeed, I could have a significantly BETTER Coefficient of Drag and, because of the vastly greater surface area, still be harder to push through the air.


As for agreement? The two of us produce the same power, but not the same power per Kg. Pound for pound, he produces more power than I do. But then, he's a Pro1 and he's half my age. He's probably in better shape by most measures -- and should be.

treebound 

Nice bike.

salcedo

Of course aero matters, a lot, but I think you are giving too much importance to your broad shoulders and his shaved legs.

First, just equipping your road bike with aero-bars would close most of the aerodynamic gap. Riding o the drops vs aero bars matters a lot more than than having slightly wider shoulders.

Secondly, the difference in your times was not just due to aerodynamics. Cyclists tend to think too much wind drag and forget about gravity. If your estimates are correct, you are talking about a 40 pound weight difference between you and the other guy. 40 pounds is like carrying two whole extra bicycles on your back. I bet that accounts for most of the time difference (if the road was hilly then I have no doubt about it).