@Mendon thanks for your honest and professional input, I (and others) appreciate it.
To be fair, I got this advice (to go with the CK hubs over P321) from (probably) the most renowned wheel builder in Aus, that has also been building wheels (for everything up to racing) for over 30 years like yourself. So, I jump on the forums to get other opinions too, but I often trust his advice over my own, Google or others I don't know only because I know his work and results.
I fully agree with everything that you're saying. But I didn't come here to claim that the CK hub is better because you can definitely 'feel' the difference, I just came stating the facts that there 'is' a
measureable difference.
Over at this thread
http://forums.mtbr.com/29er-bikes/ugly-truth-about-hub-width-wheel-stiffness-190125.html
@El Caballo does some interesting analysis on how flange dimensions affect both lateral and radial stiffness.
Using his figures, and the sinx=x approximation for small angles x between the spoke and rim, I think I can say that the difference in lateral stiffness in a CK vs a P321 Lefty hub should be around
14% stiffer for the CK. This is due to both the increased overall flange diameter and separation.
Okay, so perhaps the physics and maths isn't 100% precise as there are some assumptions and approximations made, so, maybe the difference is only 10% say?
The fact is, the 10% stiffness is real. Whether a human can perceive it or not is a qualitative argument, and since money, mass, stiffness etc. are quantitative things that's what I'm focussed on, as a personal preference. Because ultimately, that 10% stiffness isn't going to just vanish into thin air, just because I imagine it not to be there or don't feel it, surely?
For what it's worth, I ride my bike on the road 90% of the time due to frequent commuting (didn't want to buy two bikes, my preference), and I carry my bike up several flights of stairs frequently. I also constantly rely on the weight of the bike for getting it off the ground when going over obstacles, both on and off road, and recently I personally feel that the money invested in shaving 5% of the bikes mass has made a noticeable difference. So although I cannot confirm using a polygraph, I suspect that if I can physically appreciate a 5% bike mass drop, I may probably appreciate a >~10% increase in front wheel lateral stiffness. For me, the extra 10% stiffness is totally worth a $130 and 80g penalty. Personal choice. Honestly I totally agree with you: most people wont notice at all, however that doesn't mean the science isn't real and measureable.
Finally, I want to propose a counter argument to the 20g paint situation. Agreed, no-one will notice the difference for this one thing. But, apply this weight loss 50 times over the entirety of a bike's components (possible, I've done it), then you've lost 1kg, or close to 10% of the bike's mass. The same argument goes for stiffness. Maybe you'll get 10% stiffer in just one aspect of the front wheel, but if you accumulate stiffening measures across say a total of 10 aspects of the wheel (totally possible), then maybe you'll end up with a 100% stiffer wheel, wouldn't that be awesome?
Ultimately, the individual piece of the optimisation (in this instance, the CK hub), whilst individually hardly discernible, is just one piece of the puzzle that can ultimately lead to something very significant. And that's the reason I chose the CK hub.
Just my 2c (albeit with less worth being Aussie haha)! But hey let me know what you think, and thanks for the argument/discussion on the topic.
Happy grooving