Not a Venge VIAS...those are all disc-only now.

One interesting thing I just noticed about the Specialized website...the Venge models are listed under "triathlon" bikes now, and not "performance road" :-/

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Enve wheels in general (bar the 7.8 which I haven't tested) are aero turds. Much rather have the Rovals. That said, you're right, the S5 is fast and he's just being a bit Cav.

I think you need to search on ST for "Cervelo blind test" ;-)

Believe it or not, it turns out things like ultra-thin seat stays really are about visual perceptions mostly...

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I think you need to search on ST for "Cervelo blind test" ;-)

Believe it or not, it turns out things like ultra-thin seat stays really are about visual perceptions mostly...[/quote]


I think the blind test was attempting to measure people's ability to determine the difference between two (pretty similar, if I recall) bikes. That's not what we're talking about here. Sure, most people may not be able to determine the difference between an R5 and S5. That's not the same thing as there being no difference.


People also presumably can't feel the difference in aerodynamics.... and much about aerodynamics is also "visual perceptions."

I didn't mean a R and S are the same ride, both of them can be adopted if the animal on top is a racer ..

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Oh, I agree completely there. Among relatively good bikes, the equipment is 1% and the rider 99%.

A couple years ago I did some testing. Did an 7-8 mile out and back on the R then immediately after on the S. I then repeated the process with a second run on each. Same setup (same wheels, tires, tire pressure, seat height, blah, blah). I had my vectors on and had the garmin going. I sprinted all out in the same spots (both seated and out of the saddle) went up and down the same punchy climb, and rode over the same rough pavement. It wasn't blind like JohnnyO's test, but I do think I pushed the bikes harder than he did

In the end I couldn't make much of the data since I'm not good at that stuff. But for me the R was much quicker to accelerate up to a full sprint and felt much more 'jumpy' when climbing. But it seemed easier to hold a 27-30 mph sprint on the flats with the S. On the rough pavement I thought the R felt a little smoother. But that said it was very likely the placebo effect. Then again I'm all for the placebo effect - if I think something is better then it is better :P

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Matt

The thing is...the aero differences can actually be measured ;-)

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So can deflection limits, spring constants, and frequency characteristics. There are proper tools to measure CdA and proper tools to measure ride characteristics. Neither is people noodling around a parking lot.

Now a change in CdA can much more clearly predict a change in performance than a change in ride characteristics. That doesn't mean the former doesn't matter.

Just playing devil's advocate. I have the latest S5 now, and raced BWR on an AR, so I'm clearly not a True Believer in compliance bike dogma.

I guess I wasn't clear. It's not that the compliance of the system (saddle all the way through tire) aren't measurable...it's that the dominance of the system compliance is overwhelmingly in the tire. So, although one can detect compliance differences in rear triangles when tested in isolation, once you attach the super-soft spring into the "springs in series" structure, there's no measurable difference in the system compliance. The softest spring dominates.

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I've seen conflicting info on that. But Cervelo (since we're talking about them) indicates that the tire provides only about 1/3-1/2 of total system compliance. And they have, say, the front fork-steerer combo providing nearly the same amount of compliance as the front tire. That could be the reason that almost all modern aluminum bikes still have carbon forks and steerers. It might be good engineering, and not just marketing.

Of course the triangle part of the frame is very little according to this, so my rear stay argument isn't helped. But fork, seatpost, steerer, saddle, handlebar are all very significant contributors.

According to Cervelo.

So.......at the end of your test, which bike was faster overall and by much?

Yeah...we're talking the frame here, so it's the plot on the right that's applicable.

Don't forget that Damon's "Just noticeable difference" (which he tested when at Cervelo) is in the realm of 4%...so, according to that rear plot above, you'd basically have to eliminate the stiffness contribution of the frame, just for some people to be able to notice the difference. In other words, increase rear triangle compliance by 10, 20...heck, even 50%, and you won't be able to feel a difference in the system.

Oh yeah...what tire size, pressure, and body weight is assumed in those plots? I bet one could vary the overall compliance by a larger amount just dropping tire pressure by 5-10psi than could be reasonably achieved with different seat stay designs.

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Cav is just making excuses. Sprints are not just about watts and aero. Positioning and timing have as much or more to do with actually winning.

Watch the video of stage 2. Cav is caught up on the right barriers about 6th wheel. He's positioned himself there thinking that the decisive move is going to come from one of the riders in front of him and he is going to be right on it and come around. He was wrong...there is no shame in admitting that.

While Cav is on the right, another train comes up from his left that is dragging Viviani up at a higher rate of speed. Cav spots this as Viviani passes him and has to jump out of the saddle to accelerate and get onto Viviani's wheel. He's out of the saddle for a full 5 seconds and still behind when Viviani opens up his sprint. Sure enough, Viviani is still sprinting through the finish line where Cav sits down 4 seconds prior to the line.

No bike is going to save you that many watts. As great a sprinter as Cav is. He's also a pretty big cry baby.

Tom A. wrote:

Oh yeah...what tire size, pressure, and body weight is assumed in those plots?

No idea. They seem to come from here:

https://www.cervelo.com/en/Engineering-Field-Notes/Engineering-Fundamentals/Ride-Quality


They say that the charts represent "generalized examples for a road bike."

Rule of thumb:

50 grams of drag = 5 watts = .005cda = 0.5 seconds per kilometer

I should really put that in my signature line again.

@30MPH?

Only the "50 grams of drag" part, as in "when measured at 30mph".

The "5 watts" and "0.5 s/km" parts are "at typical race speeds" (i.e. over a wide range of speeds). Remember, these are rough estimates.

CdA is just CdA (and is why it's the most "universal" way of reporting drag values - no qualifications necessary)

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There is more to a sprinter's race bike that some laboratory derived aero numbers. When you're putting out 2k watts, the response and behavior of the bike is just as important.

http://sportsscientists.com/...ke-win-sprint-stage/

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Tech writer/support on this here site. FIST school instructor and certified bike fitter. Formerly at Diamondback Bikes, LeMond Fitness, FSA, TiCycles, etc.
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