mopdahl wrote:
...
brake, corner, climb, descend, etc...en mass, ...your bike handling skills, w/kg, recovery ability, etc. I would put aero WAY down the list of "needs" when evaluating my theoretical crit/road racing "wants".
...I need to be able to get low--I'm 6'3, an ex-swimmer, and built more like a NFL tight-end than a Contador. Every additional inch that I'm upright is at least 15-30 watts more that I have to put out to hold speed. The S series simply doesn't work for me b/c of the relatively tall head tube. A friend has an S3--I've ridden it--and it simply doesn't work for me, the same way that the Specialized SL3 doesn't work for me. ...I value stiffness in the BB. I value a tighter cockpit. ...enjoyment ...Feel of a bike matters. ... confidence---descending in the handling, tracking & line of my bike is key. ...the shakes ...a -17 degree stem, and in my experience, especially on descents & tight turns, that does not lend to my personal confidence in the bike. ...And for me, personally, confidence in my bike & its feel far outweigh any miniscule advantage an aero frame may have---especially for the type of riding/racing that I do.
Hi mopdahl,
Thanks for your thoughtful reply. Forgive me for editing so much of it out, like w/kg, etc. which of course are critical for best performance, but not really about the bike itself and can be trained regardless of which bike you select. I left in what I think are your key words about bike preferences. Many of them depend on components other than the frame, such as braking, etc., so I'll leave those to others if they care to address that part. These are important but can be had on any frame by choosing your preferred components.
So here's a list of
frame related characteristics I think you're building (I've left off confidence, which I hope you'll agree will come with time on any bike that's right in the other aspects):
Feel, fit / riding position, BB stiffness, "tighter cockpit"(related to fit or stiffness?), resistance to speed wobble, not a 17 degree stem.
Sorry to deconstruct your sentences so literally but I want to address each characteristic in turn.
Feel: As I wrote to Styrell above, feel is a result of many bike (and rider) characteristics and experience which I hope we can dissect below.
Fit / riding position: Sounds like you have a strong preference for very low handlebars, and a dislike of 17 degree stems. I'm not going to try to talk you out of your position here (that's a different topic), but I want to point out that 17 degree stems are good. For the same bar position (whatever yours may be), more head tube and a -17 stem is stiffer than less head tube and a -6 degree stem. We've confirmed this in the lab as part of our Project California "Lab vs. Reality" strain gauge ride testing. This knowledge went into the development of Cervelo's new geometry which first appeared on the R5ca in 2009. How does it work? Sure, the 17 stem is a touch more flexible, but the increased bracing distance between the top and down tubes at the head tube stiffens the frame against torsional loads enough to swamp the tiny difference in stem stiffness. So the
system is stiffer. System stiffness contributes to good feel, good handling, holding a line and thus confidence. So don't be afraid of a -17 stem.
BB stiffness: this can be measured and compared. Cervelos have always had very high BB stiffness, and incorporating BBright into the S5 helped increase it by another 12%.
I don't know what you mean by "tighter cockpit"?
Resistance to speed wobble: mainly comes down to (1) torsional stiffness of the frame, (2) lateral stiffness of the fork and wheels. These can be measured, and the S5 has 12% more torsional stiffness than the S3. (I'd love to talk more about speed wobble, maybe in another thread.)
Descending, handling, tracking & line: are a product of the frame's geometry and stiffness, both of which are straightforward to quantify. The S5 has perfectly normal road bike geometry (listed on the S5 web page's "Geometry" tab at
http://s5.cervelo.com/...es/2011/S5/geometry/ ) and I"ve already mentioned the 12% increase in the S5's torsional stiffness. I suspect you'd be happy with the descending handling and tracking of the S5. Have you ridden one?
Would you mind giving me your thoughts on these ideas?
Thanks,
Damon Rinard
Engineering Manager,
CSG Road Engineering Department
Cannondale & GT Bicycles
(ex-Cervelo, ex-Trek, ex-Velomax, ex-Kestrel)