BHBiker

From Lennard, can't help but see he is not a fan of the idea. What say you????
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Technical Q&A with Lennard Zinn: Weight v. wind

By Lennard Zinn
Posted Feb. 24, 2009

Weight or wind resistance; which to cut first? It depends on where and how you ride.
Photo: VeloNews file photo

Weight or air resistance?
Dear Lennard,
This question has been plaguing me and my riding buddies for the past year.

I guess there were some studies done, specifically by Ridley or Cervelo, that aero’ road frames are worth more than weight savings when selecting a bike.

So, here's my dilemma: I'm a lifetime Cat 3/Masters racer and am in the market for a new bike. My racing weight is 132 lbs and I've always tried to find the lightest equipment out there, namely because I can ride it without fear of breakage.

This latest information that an aero’ frame's benefits outweigh (pun intended) the benefits of a lighter frame has me reeling. Can you please shed some light on this conundrum? I don't ride time trials and most of my time on the road is spent in the pack in criteriums and road races.
Ken

Dear Ken,
I realize that this is the hot new category, but I think for the people actually buying those aero’ road bikes, rather than pros sponsored by their manufacturers, that the aerodynamic shape of the frame makes almost zero difference and could be the slower option for the average rider when compared to a lighter frame of equal stiffness.

In a straight-on headwind, yes, the aero’ frame is faster, and the little rough air-tripping “R-Surface” strips on the Ridley head tube and seatmast work great at keeping the passing air attached to the frame, running in smooth laminar flow with a minimum of turbulence. I’m sure that Jens Voigt’s Cervelo aero’ road bike was useful to him on his long, solo breakaways when the air was calm or the wind was parallel to his direction of travel.

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But nestled in the pack, the aero’ tubes are irrelevant, and low weight is a boon when accelerating out of corners in a criterium. On climbs, the speed is so slow that the aerodynamics of the frame tubes is irrelevant and once again, low weight is king here.

Crosswinds on large aero’ tubes are a liability beyond a very narrow range of relative wind angles (the relative wind velocity, which has both magnitude and direction, is the vector sum of the rider velocity and the wind velocity). To understand this better, look at the graph at the bottom of Hed’s aerodynamics technology page Hed’s aerodynamics technology page. Click on various wheels, and you’ll see that drag drops on any deep-section wheel as yaw angle (relative wind angle) increases at first, but all of them reach a point, generally before 8 degrees of yaw, where the drag suddenly goes up and continues to climb from then on. The same thing happens with aero’ tubes on a frame.

A strong solo rider may be able to go fast enough in a strong sidewind that the net relative wind angle is low enough to make the aero’ tubes useful, but somebody slogging along alone on a training ride or RAAM in a crosswind is not going to see a benefit. And while the pack speeds would often be enough to cut the relative wind angle even in a strong crosswind, the fact that the bike is hidden in a pack make the question of a frame’s aerodynamics moot anyway.

Stick with what you’ve been doing.
Lennard

Suzie Green

You can save a whole pound simply by drilling holes in your water bottle.

brians647

I can't wait until Pcad and Pharding read this. First the wheels won't fit on their Cervelo's, then the cabling is all messed up. Yeah, this should be good.

cslone

1. It's already being talked about in 'racing'.

B. I'll take aero over weight within reason anyday.

Cleave

Hi,

I'll add fuel to the fire. Pcad should have bought an R3 like I did since aero is immaterial when you're hanging at the back of the pack like he says he always does.

rankin116

So when did Mr. Zinn become an aerodynamics expert? What he says is just as reliable as any other joe-schmoe here on BF.

briscoelab

Zinn's points are correct. In the pack... you aren't getting any aero bonus. Climbing, speeds are low enough so that it doesn't matter much either.

But honestly, the S2 or S3 is light enough that you aren't really paying a significant weight penalty by going that route. Ride what you want!

.:Jimbo:.

So I suppose you need a graph from Mr. Zinn that has verified his findings, now that you seemed to have bought Cervelo's and Zipp's graphs and charts? It's number people like you that make it easy to sell new stuff to every new product lauch, and while I see nothing wrong with that, what bothers me are those with the theory; unless there are numbers behind it, it's utter b.s.. Numbers and cycling don't always have to go hand in hand, imo.

TrippleB

I haven't seen Garmin riders pull out those AR bikes since the 4th stage of the 2008 Tour de France, that was enough to turn me off the ARs and onto the F1.

Trek, Specialized and Giant all seem to be performing well in pro races and they have ****** downtubes that look like the flaps off of a stunt plane.

If a 37 year old rider can lead a pro peloton up a serious climb on a bike with a fat downtube, then WTH do I need aero for?

Val23708

meh. we can buy both aero and low weight. most of the high end aero frames weigh nearly the same as a non-aero frame. so this argument is worthless.

redtires

Lennard also has a degree in physics from Colorado College and has been building bikes since the late 70's. He comes from a family known for science and medicine....so...........yeah.

the beef

no

rankin116

My Dad's a Dr. so that make me smart? Are you serious? I don't care how long he's been building bikes, does'nt mean he tested his assumptions. That's all he had, assumptions.

When you're talking about numbers they do though. How does he know what benefits these frames give without testing it? He's talking out of his ass.

You guys are drinking his coolaid! He has no data to back up his point, and just because he is who he is you buy it? C'mon people.

Read this thread about it. I'm not saying anyone who posted there is and expert, but at least they take a better approach to the question than Zinn did.

garysol1 

IMHO......The fact that we are discussing it and there is no clear cut winner tells me the difference must be so small as to be negligible either way.....

celerystalksme

here's the thing though...

i'm pretty sure some of those cervelo aero frames are pretty damn light as well...i mean, isnt' the Cervelo S3 900 grams?!?!?! i mean...fudge...you're not gonna get much lighter than than, aero or not.

so why sacrifice EITHER? get a Cervelo S3 (or comparable)...light AND aero...

celerystalksme

exactly

garysol1 

I wonder if any lateral front end stiffness is sacrificed with an aero downtube. I would *think* round has to be stiffer than oval.

celerystalksme

if i remember right, the Cervelo SLC-SL had one of the highest stiffness to weight ratios of any frame in the universe (just slightly behind industry leading Cervelo R3-SL stiffness to weight ratio). i'd imagine the new Cervelo S3 is probably equal the old SLC-SL or better..

not sure what matters more though...just absolute stiffness or stiffness-to-weight ratio...

garysol1 

Or are they just talking about BB/Stay stiffness. What I am questioning is front end stiffness when your cranking on the bars left to right. Will the thinner shaped down tube have more give than a round tube.

HAMMER MAN

there is also a counter-debate with round tubes per wind deflection and aero-dynamics.

personal opinion I believe,each to their own

StanSeven

I'm always skeptical where people like Zinn are coming from. He makes his own line of bikes out of Ti and steel. I'm sure the trend towards CF and aero hurts his business. His endorsement of aero frames will only make things worse for him.

ElJamoquio

Depends on your assumptions, but generally, the biggest factor is amount of material away from the neutral axis. So if your aero tubes put a ton of material at the bottom of the headtube that otherwise wouldn't be there, that joint will be stiffer.

Of course, analyzing that joint in a vacuum is kind of worthless, since the whole tube bends.

TrippleB

Well cost is an issue...you can buy an S3 frame for $4,500 or a Felt F1 frame for $2,500. Both are sub 900kg and both are stiff...F1 Sprint is stiffer than my coffee with a bottle of Jack. I don't know about the S3 durability, but it has some of the seatstay tech from the R3SL which has had some durability issues.

$2,000 for aero that may not even benefit you? Cycling is all about enjoying technology, it is your choice. Hell, I ride a Ducati SR2 in my free time. I really dont need the extra HP and performance over my old Honda 600RR, but I like it.

As they say, engine first, bike second. If most of the pro peloton are fast with standard frames, then so am I.

.:Jimbo:.

To be truly frank about it, Mr. Zinn is not a salesman and is not selling anything. Just a fella giving out advice and info based on his findings, studies and research.

On the other hand, the likes of Cerelo and Zipp have products to sell.Thus, they come up with these perfect world test scenarios, usually consisting of perfectly straight on, consistent winds, at rather high speeds,to demonstrate their products aero-advantage. Generally, these conditions are not found in real world riding conditions, whether it is due to wind angles, disruption of air flow from surrounding objects, speeds that most of us have trouble hitting, let alone maintaining, and lastly, a frame or wheel that is perfectly in line with itself, and not flexing or warping under the loads of the cyclist.

Ultimately, cyclist buy this "advertising", and in turn buy the bike and mentally allow themselves to believe their new Cervelo with Zipp's is way faster than their outgoing large tubed Specialized or Scott just because the Cervelo Sales team said so.


To offer an analogy to best put all of this in perspective, it would be like a car company claiming they are selling the most fuel efficient vehicle on the market. Thing is, they tested the car in some vacuum like conditions where the car was able to move through with less resistance and in turn, use less power. The auto maker then publishes their results, puts it in the sales brochures and t.v ads, and let the consumers eat it up. After all, in the consumers eyes, the car companies pitch is legit, now that there are numbers backing it up. Yet real world conditions are vastly different, and now with the car in a wildly different setting and environment, trying to duplicate those mpg on your local interstate might be quite an impossible task.

eric01

Sure the S3 is a good example of both light and aero so we don't have to make any compromises. But its $4500! Unless you are buying top of the line, you do have a make a choice between weight vs. aero.

Also, lets not forget that Zinn was responding to a specific question by a reader with specific parameters. No doubt if the reader gave him a different set of parameters, that Zinn would have responded differently. Like if he said "I'm a 180 lb rider that does time trials exclusively" -- of course Zinn would say to pick an aero frame!

I was in a similar boat a couple years ago. I was torn between a cervelo soloist or an R3. I weigh about 125-130. I chose the R3. Would I have liked an S3 or an SLC? Sure! But that would have put me over my budget.