Question about ride quality of aluminium with carbon stays

John Everett wrote:

Comparing the ride quality of one bike to another has more to do with
tires, tire pressures, and saddle than tube materials. Want to change
ride quality? Change one of those.

In the 80's, when I switched from a aluminum tennis racket to a graphite
one, I could definitely tell the difference in vibration-damping
characteristics. Many others felt the same way. Was it just imagination?
Was it due to different grip material of the graphite racket? Or, what
applies to rackets dosen't apply to forks?

I have not owned anything other than all steel road bikes but am
thinking of getting a new Al bike with a carbon fork, thus my interest
in hearing the opinions.

GH

You don't have a tyre between your racket and the ball.
That's the difference.

John Everett wrote in message . ..
On 2 Sep 2003 10:22:03 -0700, (Roy) wrote:

How do the aluminium frams ride that have carbon stays? Do they help
to cut down on the stiffness of the material? Can you compare the ride
quality to anything else out there? As a reference I ride a LOOK,
Bianchi Boron XL and Bianchi MegaTi. How would the ride quality
compare to those?


Comparing the ride quality of one bike to another has more to do with
tires, tire pressures, and saddle than tube materials. Want to change
ride quality? Change one of those.


jeverett3ATearthlinkDOTnet http://home.earthlink.net/~jeverett3

Each of the above bikes has the same saddle and wheel set so it is
easy to judge them. IMO the LOOK rides feels more comfortable in 50
plus mile rides than the Mega Ti especially long flat rides. The
MegaTi climbs better than both especally with agressive climbing. The
Boron is very comfortable good for general ridding. Is is my
imagination, NO. They ride different. You have to consider angles and
the rest of the construction of the bike as well. You can make a
carbon bike ride hard by thickness of tube walls and angles. Example
Trek OCLV compared to LOOK. or You can make an aluminium fram ride
more comfortable - Cannondale compared to a Vitus 992. There are alot
of variables.

I agree that carbon mixed the aluminium is a marketing thing. There
are a few bikes that have combined chain and seat stays with good
results e.g. Bianchi Ti-Carbon, 7 Cycles to name few. It would seam
that approach would make more differce than just carbon stays.

GearóId Ó Laoi/ wrote:
You don't have a tyre between your racket and the ball. That's the
difference.



Why don't I see anybody saying that carbon forks on aluminum/steel/ti
bikes are just marketing gimmicks? Seems most folks agree that carbon
forks do handle better than steel or aluminum ones and absorb road shock
better, why is it otherwise for rear triangles?



--
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http://diabloscott.blogspot.com

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Diablo Scot writes:

Why don't I see anybody saying that carbon forks on
aluminum/steel/ti bikes are just marketing gimmicks? Seems most
folks agree that carbon forks do handle better than steel or
aluminum ones and absorb road shock better, why is it otherwise for
rear triangles?

The only thing they lean on is weight savings, the ride quality is
only alluded to or implied as a result of a few grams less weight.
Unfortunately the UCI did not step in early enough to stop this idiocy
of charging more and more for less and less... by a couple of grams
for a few thousand dollars. There is a minimum weight rule now but
it's too low mainly to not ban products already on the market that
have been developed at great expense.

Smoothness of ride arises from tires, not from frame materials. The
so called "rear triangle" is in fact a tetrahedron whose dimensions
change by no more than a few thousandths of an inch. A tetrahedron (a
six element solid figure) is stressed only in tension and compression
in the bicycle. Therefore there is no perceptible difference in road
shock through the saddle to the rider.

Head tube rake of the frame is designed to load forks primarily in
compression from road irregularities, other than from braking. Rake
angle tries to match the size of the most common road irregularities
encountered a front wheel of conventional diameter so that it fork
sustains primarily axial compression.

Frames, other than ones with suspension elements, do not absorb shock.
Ride comfort can only be changes by wheelbase change, the longer the
chainstays, the more comfortable the ride. Other than that, the
pneumatic tire does the rest.

Jobst Brandt

On Thu, 04 Sep 2003 05:06:04 +0950, DiabloScott wrote:

Why don't I see anybody saying that carbon forks on aluminum/steel/ti
bikes are just marketing gimmicks? Seems most folks agree that carbon
forks do handle better than steel or aluminum ones and absorb road shock
better,

Your premise is wrong. People do say that carbon forks do not "handle
better" than steel or aluminum, and they do not absorb road shock better.

The differences, if any, in shock absorbtion between various forks is an
order of magnitude less than the shock absorbtion of the tire. So, you
could not tell if there were an advantage, since the advantage is less
than that last puff of air you put in your tire.

Thre is a distinction between carbon forks, and carbon pieces in a frame,
from this point of view, though. Carbon forks are now competitive in
price with aluminum or steel. The big difference is weight, and even
there carbon and aluminum are competititve. But carbon stays on a frame
seem to double the price, for no benefit.

--

David L. Johnson

__o | A mathematician is a machine for turning coffee into theorems.
_`\(,_ | -- Paul Erdos
(_)/ (_) |

Seems most folks agree that carbon
forks do handle better than steel or aluminum ones and absorb road shock
better, why is it otherwise for rear triangles?

it ain't. carbon rears, just like seat posts & forks, /do/ take a lot
of the sting out of the road. they're not stiffer overall, or sloppier
overall, but they /do/ take a lot of the road vibe out.

truthfully, i was skeptical until i rode some of this stuff myself. you
have two very dissimilar materials in these composites. the modulus of
graphite fiber is very high but the modulus of the resin that holds it
together is very low. in unstressed steel reinforced concrete and
pre-stressed reinforced concrete, the difference in performance of the
former is that it is initially more "flexible" until the steel starts
picking up more of the load. pre-stressed concrete is "stiffer" but has
a lower failure stress because the pre-load detracts from the total
available strength of the steel.

similarly, fibers embedded in resin, for current fabrication methods at
least, are not pre-stressed and this means that for a small portion of
the load, you're merely straining plastic, not high modulus fiber.
great for small amplitude road vibration damping. the result of large
strains is of course dependant on the fiber, hence these frames remain
stiff overall.

it's also interesting to note that one of the fatigue modes for
composites has been the "loosening" of the fiber in the matrix - the
fiber is free to slide. this gives a mushy feel because you're
basically just riding resin.

jb

Jobst Brandt [/i]
Diablo Scott writes:

Why don't I see anybody saying that carbon forks on aluminum/steel/ti bikes are just marketing
gimmicks? Seems most folks agree that carbon forks do handle better than steel or aluminum ones
and absorb road shock better, why is it otherwise for rear triangles?

The only thing they lean on is weight savings, the ride quality is only alluded to or implied as a
result of a few grams less weight. Unfortunately the UCI did not step in early enough to stop this
idiocy of charging more and more for less and less... by a couple of grams for a few thousand
dollars. There is a minimum weight rule now but it's too low mainly to not ban products already on
the market that have been developed at great expense.

Smoothness of ride arises from tires, not from frame materials. The so called "rear triangle" is in
fact a tetrahedron whose dimensions change by no more than a few thousandths of an inch. A
tetrahedron (a six element solid figure) is stressed only in tension and compression in the bicycle.
Therefore there is no perceptible difference in road shock through the saddle to the rider.

Head tube rake of the frame is designed to load forks primarily in compression from road
irregularities, other than from braking. Rake angle tries to match the size of the most common road
irregularities encountered a front wheel of conventional diameter so that it fork sustains primarily
axial compression.

Frames, other than ones with suspension elements, do not absorb shock. Ride comfort can only be
changes by wheelbase change, the longer the chainstays, the more comfortable the ride. Other than
that, the pneumatic tire does the rest.

Jobst Brandt [/quote]



Interesting info Jobst; although I count eight members in the rear “triangle” including the brake bridge (bottom tube and seat tube members are very small of course).

Rather than “road shock” I should have written “vibration dampening” which is what the reviews and marketing usually attribute to the carbon fiber – so we’re talking about high-frequency buzz like you’d get on a chip seal road surface rather than large bumps. Are you saying vibration dampening is a non-issue? Why would the buzz attenuation be any different in the front than the back?

And reviewers DO write about the better handling characteristics of carbon forks, although mostly they site the stiffness rather than any material property. Is this just nonsense?

So – do you think carbon forks are marketing gimmicks or not? If so, why aren’t you as vocal against carbon forks as you are against carbon stays?

[quote][i]Originally posted by David L. Johnson wrote:
Your premise is wrong. People do say that carbon forks do not
"handle better" than steel or aluminum, and they do not absorb road
shock better.
The differences, if any, in shock absorption between various forks is an
order of magnitude less than the shock absorption of the tire. So, you
could not tell if there were an advantage, since the advantage is less
than that last puff of air you put in your tire.
Thre is a distinction between carbon forks, and carbon pieces in a
frame, from this point of view, though. Carbon forks are now competitive
in price with aluminum or steel. The big difference is weight, and even
there carbon and aluminum are competititve. But carbon stays on a frame
seem to double the price, for no benefit.
--



A quick check through my catalogues finds one steel fork for $30 and
one aluminum fork for $40 while the carbon forks range from $90 to
$500. On the Eddy Merckx frames (Leader and Race) the carbon rear stays
increase the price by about $300. So it seems that carbon rears
increase the price of a frame by about the same amount as a carbon fork
does; huge generalization of course but much less than your “double the
price” figure.

So David - do you think carbon forks are marketing gimmicks? If you
can’t tell the difference in ride quality between aluminum and carbon
forks, and the weight is about the same, why aren’t you as vocal against
carbon forks as you are against carbon stays?

I’m not trying to be argumentative here, it just seems that most of
the things people are writing against carbon stays can also be written
about carbon forks. I’m curious why no one has done so. I’m open to
the idea that carbon forks really are marketing gimmicks but it seems
they have near universal acceptance while carbon stays have near
universal contempt.



--
Check out my bike blog!

http://diabloscott.blogspot.com

--------------------------
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Diablo Scott writes:

Why don't I see anybody saying that carbon forks on
aluminum/steel/ti bikes are just marketing gimmicks? Seems most
folks agree that carbon forks do handle better than steel or
aluminum ones and absorb road shock better, why is it otherwise
for rear triangles?

The only thing they lean on is weight savings, the ride quality is
only alluded to or implied as a result of a few grams less
weight. Unfortunately the UCI did not step in early enough to stop
this idiocy of charging more and more for less and less... by a
couple of grams for a few thousand dollars. There is a minimum
weight rule now but it's too low mainly to not ban products already
on the market that have been developed at great expense.

Smoothness of ride arises from tires, not from frame materials. The
so called "rear triangle" is in fact a tetrahedron whose dimensions
change by no more than a few thousandths of an inch. A tetrahedron
(a six element solid figure) is stressed only in tension and
compression in the bicycle. Therefore there is no perceptible
difference in road shock through the saddle to the rider.

Head tube rake of the frame is designed to load forks primarily in
compression from road irregularities, other than from braking. Rake
angle tries to match the size of the most common road irregularities
encountered a front wheel of conventional diameter so that it fork
sustains primarily axial compression.

Frames, other than ones with suspension elements, do not absorb
shock. Ride comfort can only be changes by wheelbase change, the
longer the chainstays, the more comfortable the ride. Other than
that, the pneumatic tire does the rest.

Interesting info Jobst; although I count eight members in the rear
"triangle" including the brake bridge (bottom tube and seat
tube members are very small of course).

Look up tetrahedron in you math book and you'll find that it has four
surfaces and six edges. The brake bridge plays no role in load
carrying. It is there to mount the brake and adds nothing to the
strength of the figure. The six elements are 2-chainstays,
2-seatstays, seat tube and rear axle.

Rather than "road shock" I should have written "vibration dampening"
which is what the reviews and marketing usually attribute to the
carbon fiber; so we’re talking about high-frequency buzz like you’d
get on a chip seal road surface rather than large bumps. Are you
saying vibration dampening is a non-issue? Why would the buzz
attenuation be any different in the front than the back?

It may not be obvious but the seat and chainstays are thin tubes
because they carry only compressive and tensile forces, unlike the
large tubes of the frame that carry torsion and bending. That's why
the "rear triangle" is made of such slender tubes.

And reviewers DO write about the better handling characteristics of
carbon forks, although mostly they site the stiffness rather than
any material property. Is this just nonsense?

That's the point. Reviewers are fashion critics and rarely have any
idea about what they write. It needs to sound good but contain no
data or proofs of reality. The unwitting public is so used to this
kind of spin doctoring that they don't even notice it anymore and when
asked repeat what the article alluded to but never said.

So – do you think carbon forks are marketing gimmicks or not? If
so, why aren’t you as vocal against carbon forks as you are against
carbon stays?

Absolutely. In fact, until they came on the market we never heard of
a fork disintegrating while riding along. This is a relatively common
occurrence with carbon forks. You won't see me descending the Stelvio
pass with a carbon fork.

http://tinyurl.com/len5

Having a fork fail at any one of these hairpin turns is easily fatal.

Originally posted by David L. Johnson wrote:
Your premise is wrong. People do say that carbon forks do not
"handle better" than steel or aluminum, and they do not absorb
road shock better.
The differences, if any, in shock absorption between various
forks is an order of magnitude less than the shock absorption of
the tire. So, you could not tell if there were an advantage,
since the advantage is less than that last puff of air you put
in your tire. There is a distinction between carbon forks, and
carbon pieces in a frame, from this point of view,
though. Carbon forks are now competitive in price with aluminum
or steel. The big difference is weight, and even there carbon
and aluminum are competitive. But carbon stays on a frame seem
to double the price, for no benefit. --

So how about learning how to write to wreck.bike in the net etiquette?
Your character set and inclusions are hard to decipher. If you haven't
noticed, the protocol is to add a "" before anything cited, thus
"" means from three postings ago with two subsequent responses.

A quick check through my catalogues finds one steel fork for $30 and
one aluminum fork for $40 while the carbon forks range from $90 to
$500. On the Eddy Merckx frames (Leader and Race) the carbon rear
stays increase the price by about $300. So it seems that carbon
rears increase the price of a frame by about the same amount as a
carbon fork does; huge generalization of course but much less than
your "double the price" figure.

And you think this is a good indicator of anything useful? Why do
"stylish" bicycle glasses with less than a dollar's manufacturing
cost, sell for $60+. For the same reason. They're IN! Gotta have
it.

So David - do you think carbon forks are marketing gimmicks? If you
can’t tell the difference in ride quality between aluminum and
carbon forks, and the weight is about the same, why aren’t you as
vocal against carbon forks as you are against carbon stays?

This also doesn't work well. If you want a response from David, put
the request in a response to his posting. However, I'll offer that
they are entirely marketing gimmicks and hazardous ones at that.

I’m not trying to be argumentative here, it just seems that most of
the things people are writing against carbon stays can also be
written about carbon forks. I’m curious why no one has done so.
I’m open to the idea that carbon forks really are marketing gimmicks
but it seems they have near universal acceptance while carbon stays
have near universal contempt.

The idea of carbon came to make a bicycle lighter. In response steel
frames have become lighter and are still more reliable than "plastic?"
Now that we have a minimum weight, they have to claim something else.
Your vibration damping is pretty far fetched. There may be an
acoustic difference. You may have noticed that light weight tires
make a rushing sound whose frequency is able to resonate in a steel
frame. Other materials are so dead that they don't do that.

Jobst Brandt

On Thu, 04 Sep 2003 08:55:57 +0950, DiabloScott wrote:


And reviewers DO write about the better handling characteristics of carbon
forks, although mostly they site the stiffness rather than any material
property. Is this just nonsense?

Reviewers write all sorts of nonsense. Think about it. Have you ever
read a negative review of _any_ high-priced bike component in Bicycling?
Can they _all_ be worth the money?

A quick check through my catalogues finds one steel fork for $30 and one
aluminum fork for $40 while the carbon forks range from $90 to $500.

I*can find steel forks for $90 (Sheldon has one), and probably more are
around. If you buy it as part of the bike, the difference in price will be very
small.

On
the Eddy Merckx frames (Leader and Race) the carbon rear stays increase
the price by about $300.

But there are others that are only offerred with the carbon stays, and
those tend to be the priciest.

So it seems that carbon rears increase the price
of a frame by about the same amount as a carbon fork does; huge
generalization of course but much less than your “double the price”
figure.

Perhaps my generalization was a bit high, but $30 to $90 is $60 for your
prices to go from steel to carbon fork, versus $300 for the rear stays.

So David - do you think carbon forks are marketing gimmicks?

Like I said, they are lighter than steel, and available at roughly the
same price. I have a carbon fork -- which I got from a swap meet for $25.
Works fine. Is it magic? Will it make the ride smooth? No. The $400
forks are those that are all-carbon, which I wouldn't ride on a bet.

If you can’t
tell the difference in ride quality between aluminum and carbon forks, and
the weight is about the same, why aren’t you as vocal against carbon
forks as you are against carbon stays?

I'm not vocal against either; I just don't think they are worth a lot of
extra money.

I’m not trying to be argumentative here,

Sure you are

it just seems that most of the
things people are writing against carbon stays can also be written about
carbon forks. I’m curious why no one has done so.

You keep saying that as if it were true.

I’m open to the idea
that carbon forks really are marketing gimmicks but it seems they have
near universal acceptance while carbon stays have near universal
contempt.

Your comparisons -- even with your price quotes -- are faulty. Forks are
easily-replacable components. Carbon forks are available from every shop
and catalogue company for a price that is competitive with what a decent
fork of any other material would cost. The difference in price is small.
For instance, Nashbar sells an aluminum fork for $80, and a carbon, on
sale, for $50. OK, the carbon is their own brand; they have an Easton
for $90.

On the other hand, carbon stays will save a lot less weight than carbon
forks (vs steel, certainly, and likely aluminum as well), for a lot more
money. Any other advantage they claim is marketing hype. They add a
large premium to the price of the frame.

--

David L. Johnson

__o | Accept risk. Accept responsibility. Put a lawyer out of
_`\(,_ | business.
(_)/ (_) |