Where to clamp bike to work on it?

Ben C wrote:
On 2008-08-10, jim beam wrote:
Ben C wrote:
[...]
absolutely the tire does - that's what it's for. and i expect the order
of magnitude difference to be at least 2. but that /still/ doesn't mean
carbon doesn't attenuate because it does. nobody [hopefully] disputes
that rubbers absorb vibration. the polymers in cfrp resins aren't the
same as rubbers, but they're still subject to hysteresis, and thus,
there is a time component to any strain.

as has been discussed here many times before, attenuation may not be the
primary reason for using cfrp, but it's a fantastic side-benefit.
tennis rackets are an example outside of bikes. soft pneumatic ball,
polymeric strings, vibration-absorptive grip - no first order reason to
worry about attenuation in the frame material, right? but no. carbon
is /the/ material of choice because the contribution the material makes
to the overall performance of the interaction is significant for the
user. if you dags on tennis racket materials, i'm sure you'll find some
spectral analysis. unlike bikes. because all bike guys do is fight to
preserve their ignorance.


as a follow-up, do you think you /can't/ tell the difference in
vibration between metal and wood? cfrp is very closely related to wood,
so it's a very simple concept translation.

I believe CFRP and wood absorb vibration in a way that steel doesn't
(we've mentioned hammers before and why you need a thick rubber grip if
the handle is made of steel instead of wood), but I don't know if I
could tell the difference for just a seatpost. In the whole bike, maybe.
But this is just a guess.

well, as mike jacoubowsky pointed out, the /amount/ of the stuff is
definitely going to make a difference. most of my seat posts are
extended in the 20cm range. for the "old skool" that insist on riding
bikes with top tubes right up to their 'nads, i don't see it making the
slightest difference at all.



Another straw to clutch at is that maybe there's more to life than blind
tests. You might find for example that people had fewer tingly hand
problems or something after a long ride on a CF bike _even if_ they
couldn't actually recognize the bike themselves in a blind test over a
few kilometres.

We mentioned racing drivers before and how for all their loquaciousness
they're often completely wrong about what "feels faster". But still give
them a better car and they can actually do a better lap time, so some
part of their unconscious mind at least must know what it's doing.

Maybe it's OK to fail blind tests. Maybe you can genuinely appreciate
fine wine even though you had to be told that's what it was. Just
because something can only be perceived when you know what you're
looking for it doesn't necessarily follow that the perception is a total
illusion.

skepticism is healthy. blind, persistent, closed minded ignorance is
not. see above.

On Aug 8, 1:16*pm, Derk wrote:
wrote:
Do you know of any blind testing, with the posts wrapped with tape, in
which riders notice any difference between seat posts?

TOUR tested/measured seatposts and found that titanium seatpost are more
comfortable than any other seatpost.

Derk

Any luck digging up this article? I still have not placed that online
order, mainly because I'm not sure if I want to include a new seat
post. I could sure use the rain gear with what the weather has been
doing around here, however.

I can live with the ride I have now. As I said, most of the roads I
ride are pretty smooth and the bike feels really good around 110PSI
(700x25 tires). It's actually more comfortable than some of the all-
aluminum (except carbon forks) bikes I test rode, all of which were
inflated to 95-100PSI per the shops compressor. Carbon rear triangle,
tires, wheels, who knows - but I like it. Part of me thinks a carbon
post may make it a smidge more comfy. Part of me is starting to think
maybe a different seat would be the way to go, although that's a hard
switch to make since they're so specific to how they fit ones rear
that trial and error gets expensive quick. Another part of me is
thinking that maybe I should just leave the extra padding in my wallet
and ride what I've got - an option made even more attractive by the
fact that my dirt bike is ready for a new top-end.