I'm confused. Are you bragging about bike technology being awesome, or saying aero bikes suck?

I'll try to find the videos online but with Cav was busy knocking Veelers down and Marcel was closing the huge gap Andre opened up on Stage 10 you can clearly see the moment that Greipel hits the bricks and his rear wheel begins skipping side to side as he tries to fight off Kittel.

Again on the Champs Kittel goes early and Andre and Cav split sides to overtake him in the final 100 meters. Cav's bike is bouncing it nearly takes him out and Greipel fades in the last 25 meters.

Aero road bikes do not suck and certainly the Spec and Ridley have enough racing pedigree and palmares to be among the best offered. Early criticism of all aero road bikes has been of the harshness of the ride. I think one of the keys to getting widespread acceptance for these bikes would be a way to add significant improvements in ride quality. Roubaix meets Venge or Domane meets SpeedConcept. Zipp glosses over their VCLC™ vibration-reduction technologies too often I think. I suspect it is because it is difficult to measure and quantify. There isn't a gram scale for comfort.

-SD

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https://www.kickstarter.com/...bike-for-the-new-era

Cav's rear wheel jumped damn near 8 inches in the air at the finish.

The evidence that this has anything to do with the bikes being aero is what I'm missing.

The cross section of aerodynamic frame tubes typically makes them less compliant as the major axis of the shapes is oriented in the same direction you'd want the movement to occur. What's worse is that the bending, torsion, and lateral flex is more likely with these airfoil shapes as the cross section is narrowest along these loads requiring additional material further reducing the possibility of comfort inducing layups.

-SD

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https://www.kickstarter.com/...bike-for-the-new-era

Is Kittel's frame by any chance stealth areo in the same sense that the Madone or Rca or Scott Foil is?

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Kat Hunter reports on the San Dimas Stage Race from inside the GC winning team
Aeroweenie.com -Compendium of Aero Data and Knowledge
Freelance sports & outdoors writer Kathryn Hunter

So in theory a bike where it is wide in the x axiz, but thin in the Y axis (total opposite of aero) is your perfect Paris Roubaix bike....or get a softride. So the aero engineering problem and the compliance engineering problem are totally orthogonal and you guys are essentially handcuffed with this engineering trade off scenario.

not totally orthogonal.
The s5 for instance has a seat stay feature that adds some compliance while improving aerodynamics.

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Kat Hunter reports on the San Dimas Stage Race from inside the GC winning team
Aeroweenie.com -Compendium of Aero Data and Knowledge
Freelance sports & outdoors writer Kathryn Hunter

Yeah, they're not orthogonal nor mutually exclusive. They are however, much harder to quantify their trade-offs. Even more so than type of carbon fiber used or the carbon fiber lay-up order. Changing the shape will affect the aero properties and the dynamic loading capabilities. A sweet spot combination would be almost impossible b/c every rider, every road, every race is different...even w/in that race.

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______________________________________________________
Sub-9 IM. Navy SeaBee deep sea diver. Can Do!

Paris Roubaix presents additional challenges but in general, round-ish tubes are good for compliance. A softride would be less optimal as the saddle to pedal distance varies by a large amount over the amplitude of the cobbles I'd think. That and the UCI legality issue.

Handcuffed? No, it presents challenges, yes. Innovation is the offspring of such challenges.

-SD

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https://www.kickstarter.com/...bike-for-the-new-era

Congrats on a GREAT tour for felt!

When can we expect to see the FRD hit the shelves? I'm in Australia btw.

The FRD projects do not follow a typical model year. The frames we've developed for Argos are not currently planned for distribution but that may change given the reaction to the successes at the Tour and the uptick in demand. The TeXtreme material and expanded polystyrene 2 piece molding process makes them very very costly to produce and the time it takes to create these unique frames would create a very limited production run.

-SD

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https://www.kickstarter.com/...bike-for-the-new-era

Dave,

I'm a big fan of Felt bikes (I own one), but I'm not sure I agree with your assessment of Stage 21. What I saw was a surprisingly good team leading out Kittel while Cav ran out of lead out men and Gripel's team took the last 1K off.

Cav and Gripel both had a faster turn of speed than Kittel in the last 2-300m but just couldn't overtake him. Bouncing and all.

Are you suggesting that if they weren't bouncing so much they would have overtaken Kittel?


And here's a video of Stage 10. Check out 0:42-0:47. They both bounce, no?

http://www.steephill.tv/...69995267&yr=2013

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Trek Madone 5.9SL
Felt B12 (sold)

i have no idea what kittel is riding but i would be surprised if he's not riding a standard F series mold, just like degenkolb. this team, and this bike, is the story of the year in sprinting. remember degenkolb won a stage on an F series in the giro. if kittel were not on this team argos shimano is still a heavy duty sprint squad, even if it were only with degenkolb. this team has at least 5 sprint victories, according to my memory, in the 2 biggest grand tours this year.

the F series bikes are different than just about every other bike in the peleton. they are very long, and very low, and if you look at how kittel first, but even more notably degenkolb, rides these bikes, the F series are perfect for them. now, you might say that, heck, they could win on anything. however, if you consider who is really riding the bikes that suit them, i think if argos shimano were riding cervelos these two sprinters would be having a very hard time figuring out how to get the bikes to work for them. conversely, i think cervelo's R and S series bikes are great for talansky and hesjedal (as would felt's AR series be good for them).

the F series bikes are very long, very low, long wheelbase, very laterally stiff, and that vertical compliance dave talks about is part the way the bike is built - the layup, the shape - but i think part of it is just in that long/low geometry.

i don't know why cavendish rides a venge. i'm no expert, and especially not in sprinting. but i don't know why he wouldn't choose a tarmac. smarter people than i will have to explain that to me.

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Dan Empfield
aka Slowman

Because they fly!

Well because the Venge has less drag, so it goes faster....

As long as its stiffness is sufficient (almost certainly is)

and as long at its compliance is sufficient (this seems to be in dispute! smarter people than I will have to explain that to me)

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Kat Hunter reports on the San Dimas Stage Race from inside the GC winning team
Aeroweenie.com -Compendium of Aero Data and Knowledge
Freelance sports & outdoors writer Kathryn Hunter

"Well because the Venge has less drag, so it goes faster. As long as..."

there's the rub. i just don't think the difference in aero tube sections makes up for what you lose in the other performance elements of the frame. if i take what you write at face value, we should be seeing all these guys should be wearing very different clothing, helmets, shoe covers, than they now use. why don't they wear shoe covers on days where the weather is not hot? probably because they tighten their buckles before the sprint. the performance of shoes, frames, wheels, tires, is more important than the on-paper aero benefit. apparently.

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Dan Empfield
aka Slowman

You can't draw significant conclusions. What you have is a mass-spring-damper system (IOW, a structure with damping) with a forcing function (aerodynamic forces, a forcing function provided by the road surface, an inertial mass moving relative to the bike (i.e., the rider), etc. On the cobbles, if you visualize this as a simple single-degree-of-freedom system, you could say that given the lighter weight of the other riders compared to Kittel (is he really 86 kg?), the combined weight of the bike+rider plus the stiffness of the bike tuned into the forcing function of the cobbles (i.e., the distance between gaps in the cobbles). If the forcing function is at the same frequency as the isolation frequency, all hell breaks out. If they were going slower, they respond statically. Faster? No excitation at all (or rather, transfer function is rolling off quite a bit).

I'd be wary of designing in features like "wheelbase elongation" or "saddle displacement" as all those are potentially strain energy mechanisms. I'd rather convert the all the work provided by pedaling into kinetic energy moving forward rather than significant strain energy to get me to a gross displaced state. Now clearly if some strain energy is utilized to minimize dynamic response, that is one thing. However, unless you characterized the cobbles as a forcing function and implemented that in the design of the frame along with rider weight and other critical things affecting the dynamic structural response of a design, it's marketing BS.

So did you perform any sort of linear or nonlinear direct transient or modal transient structural dynamics in the design of the frame?

BTW - not knocking the bikes. I own an older Felt track bike, which by the way is stiff as all get out. Completely wears me down physically compared to my older Specialized carbon road bike. But it serves a different purpose.

I love it when insiders post inside here. As for this topic, could you explain why vertical deflection of the frame is significant in comparison to deflection of the tires? It seems like the tires should deflect way more than the frame. Does it have to do with resonance, or are the frames deflecting vertically way more than I thought?

Thinking out loud, if one rider is bouncing 8" in the air and another is firmly planted after riding the same speed on the same course, one frame must be much much more compliant than the others.

And the $100 million question is whether pros avoid aero frames for good reasons, or insane ones.

We like to believe they are all professional and making smart decisions guided by smart advisors, but, as Josh at Zipp has shown us in the lightweight wheels in the tour thread, is not always the case. And I have heard at least one other example of exactly that sort of thing from another person in the trenches (wanting the lighter frame, even though the bike can't be any lighter)

Some things are knowable. Like that you aren't losing power transfer by chosing an aero frame. We know that.

Some things are harder to know - does an aero frame feel or handle bad when you throw a 1,500 watt sprint at it? Maybe. I don't think so but I don't know how to prove it short of a double blind test.

Cav and Greipel clearly don't mind it much.

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Kat Hunter reports on the San Dimas Stage Race from inside the GC winning team
Aeroweenie.com -Compendium of Aero Data and Knowledge
Freelance sports & outdoors writer Kathryn Hunter

Hey Dave, would the difference in vertical compliance between any 2 bikes be able to make up for the 6-8" Cav's bike jumped? I'm assuming vertical compliance is code for elasticity of the frame - and there would have to be significant differences in bikes to make up for that jump. The energy involved in that move would seem to be greater than any carbon monocoque frame would absorb. Plus, there are the tires which (I assume) damp much more than the bike itself ever could.

Are you saying that the frame itself absorbs these bumps/jumps, or the different characteristics allow the riders to avoid them in the first place?

Or rider. As I mentioned above, it's a mass-spring-damper system. Or m*a(t)+c*v(t)+k*x(t)=F(t). If you put Cav and Kittel on the EXACT bike, k is the same. In simplest terms, for a SDOF system, natural frequency is sqrt(k/m)/(2*pi). If F(t) has frequency content near that value, response is amplified (think Tacoma Narrows Bridge). In one case, with the correct F(t) and m, Cav would be bouncing all over the place. Yet, for the same forcing function Kittel is humming along. Conversely, change the frequency content of F(t) and Kittel is bouncing like a jackrabbit and Cav is sliding along a calm lake. Point is, a single parameter, in this case k (stiffness), doesn't completely define the response.

The energy involved in that move would seem to be greater than any carbon monocoque frame would absorb. Plus, there are the tires which (I assume) damp much more than the bike itself ever could.

People tend to assume that the flex in tires is much much greater than the flex in a frame. RIDE magazine and others routinely measure how much a frame flexes with a std load. It varies by a big % from frame to frame buts its reasonable significant.

This is pretty old data but its a start

http://www.sheldonbrown.com/...inard_frametest.html

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Styrrell

I think you might want to research the concept of "springs in series", and then revisit those links...

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http://bikeblather.blogspot.com/