Carbon Fiber Seat Stays = Better Ride?

"Steve Sr." wrote in message
...
I have seen carbon fiber seat stays being advertized as improving the
"comfort" and the ride "quality" of a bike. Serotta even goes so far
as putting a bearing at the dropout end on their high end bikes to
allow the seat stays to flex and act as springs to soften the ride. Or
at least this is what is claimed. Other manufacturers make similar
claims.

So given a regular full titanium frame like a Litespeed Tuscany how
much if any difference would be made by having the seat stays made of
carbon fiber? Would the difference be noticeable or not? Has anybody
done any _quantatative_ measurements or studies on this or is it all
subjective?

You want a "better" ride? Then get wider tires. Instead of running 700x20 or
23mm wide tires, get something like a *true* 700x25 and pump up to 100psi.
Remember, wider tires = more air volume = more comfort. Plus, wider tires =
lower rolling resistance. That will provide more comfort and "better" ride
than carbon stays....

Steve the elder writes:

I have seen carbon fiber seat stays being advertized as improving
the "comfort" and the ride "quality" of a bike. Serotta even goes so
far as putting a bearing at the dropout end on their high end bikes
to allow the seat stays to flex and act as springs to soften the
ride. Or at least this is what is claimed. Other manufacturers make
similar claims.

So given a regular full titanium frame like a Litespeed Tuscany how
much if any difference would be made by having the seat stays made
of carbon fiber? Would the difference be noticeable or not? Has
anybody done any _quantitative_ measurements or studies on this or
is it all subjective?

If you consider the concept of off axis loading of a seat stay (the
point where they shot themselves in the foot) you should note that a
flexing strut changes length axially by the cosine of the angle of
deflection. For instance, the cosine of 5 degrees on an 18" seatstay
is about 0.070". I doubt that you have had any seatstay flex visibly
and therefore, because the cosine of 1 degree is 0.9998, an angle that
would be visible, there is no cushioning.

This has been a bugaboo since the early days of 'diamond' bicycle
frames. See Hetchins frames of 50 years ago. It's all hype. it's
less that a stroke of a frame fit pump in the rear tire tire at
100psi.

http://www.hetchins.org/100.htm

Steve Sr. writes:

I have seen carbon fiber seat stays being advertized as improving the
"comfort" and the ride "quality" of a bike. Serotta even goes so far
as putting a bearing at the dropout end on their high end bikes to
allow the seat stays to flex and act as springs to soften the ride. Or
at least this is what is claimed. Other manufacturers make similar
claims.

I think this is just B.S., but you have to find out for yourself. Go
to a dealer and ride one of these heavy beasts. Hint: Next Year Your
Bike Dealer Will Be Touting The Lightness Of All-Aluminum Framesets!

A carbon rear triangle probably beats a frame made entirely of
aluminum, but maybe not by more than the addition of 2mm of rubber on
your rear tire.

I liked my 1998 TREK 2300, which had 3 main tubes of carbon fiber. No
carbon fiber in the rear aluminum triangle, but it had outstanding
compliance, which is probably what allowed TREK to sell the same
frameset for 8 years, unchanged. That's gotta be a record with these
hi-tech framesets. Mine split at the seat lug - how did YOU break
your TREK frame THIS MONTH ?!?!

I think that vibration absorption on the front end is proably more
important than on the rear because the front end of the bike has less
load and is therefore less damped and will therefore vibrate more
easily and for longer periods on a rough road surface with your 160
psi rock-hard tires.

Just my 2c.

- Don Gillies
San Diego, CA

Don't think that carbon seatstays matter that much.

Re "backside" comfort only, my 853 steel bike is seemingly more
comfortable than my Litespeed Siena with carbon seat stays. But the
Litespeed tracks better, so more comfortable going downhills. This
probably has nothing to do with the carbon seatstays, but just pointing
out numerous measures of comfort on a bike.

My wife has a alumnium Klein with carbon seatstays, and she says it is
both more comfortable and tracks better than her old Trek 5000-all
carbon frame.

At the other end I didn't get the Litespeed Real Design fork that came
with the bike, as it has a harsh reputation and I ride with two
Litespeed owners who replaced it. I replaced it with Reynolds Ozou and
very happy with it--same of less amount of road noise comes through the
front end (top of bars double tape) as on 853 w Kestral fork.

Good luck
j

Steve Sr. wrote:
I have seen carbon fiber seat stays being advertized as improving the
"comfort" and the ride "quality" of a bike. Serotta even goes so far
as putting a bearing at the dropout end on their high end bikes to
allow the seat stays to flex and act as springs to soften the ride. Or
at least this is what is claimed. Other manufacturers make similar
claims.

So given a regular full titanium frame like a Litespeed Tuscany how
much if any difference would be made by having the seat stays made of
carbon fiber? Would the difference be noticeable or not? Has anybody
done any _quantatative_ measurements or studies on this or is it all
subjective?

Thanks for your thoughts.

Steve

it should have a noticably softer ride. materials people are very
familiar with the superior shock transmission characteristics of
composites. that's why tools like hammers that otherwise cause
repetitive strain injuries are so often made with composite shafts. [in
this case, wood can also be called a composite.]

the trouble with this group however is that the people making the
loudest "it makes no difference" noises would never do anything
definitive like rent instumentation that would quantify the situation -
it would prove them luddites. as for actually /riding/ a bike with such
new fangled technology? well, that's just not going to happen. no
siree bob.

jim beam wrote:

snip

Has anybody done any _quantatative_ measurements or studies on this
or is it all subjective

Has anyone, including manufacturers, tried to quantify this with strain
gauges and instrumentation? Just curious.

Earls61 wrote:
jim beam wrote:

snip

Has anybody done any _quantatative_ measurements or studies on this
or is it all subjective

Has anyone, including manufacturers, tried to quantify this with strain
gauges and instrumentation? Just curious.

not aware on any bike manufacturer publishing it, but it's easily done.
just need a vibration analyzer. shock transmission spectra for carbon
composites are quite different to steel or aluminum. tennis racquet
manufacturers are much more forthcoming on this subject.

jim beam wrote:

it should have a noticably softer ride. materials people are very
familiar with the superior shock transmission characteristics of
composites. that's why tools like hammers that otherwise cause
repetitive strain injuries are so often made with composite shafts. [in
this case, wood can also be called a composite.]

the trouble with this group however is that the people making the
loudest "it makes no difference" noises would never do anything
definitive like rent instumentation that would quantify the situation -
it would prove them luddites. as for actually /riding/ a bike with such
new fangled technology? well, that's just not going to happen. no
siree bob.

Tell ya' what then... due to the total lack of any measurements (gee,
why do you suppose the manufacturers didn't try to quantify the
tremendous amount of improvement???), we'll have to settle for you
explaining to us all how much that carbon fiber seat stay
"compresses", and how, under what conditions. And then you can
compare that amount of compression to that in the tire during an event
that would compress the seat stay, and explain to us all how the
difference would be noticeable to the rider.

That'll do...

Mark Hickey
Habanero Cycles
http://www.habcycles.com
Home of the $695 ti frame

I haven't seen one for bicycles.. but there is a lot of data available
in engineering.
Vibration damping is a known property, it is measured and is often a
design driver. CF has "better" damping than Steel/Alu/Ti .. All else
being equal there WILL be a difference in ride characteristics, how
much a difference might be noticeable to you or may well be minutia for
a lab to determine.

How this fact is applied in each case is a different matter, the
bicycle industry has a long history of marketing driven design and
engineering decisions. This tends to leave people jaded about claims
like these.

Please explain why compression is an issue?
Grey/Black cast iron does not compress, yet its vibration damping
characteristics are why all the best machine tools use it for frames
and beds.

Don't confuse two different phenomina.