The history and development of the Carbon Fiber bicycle...

Uploaded by Google on 24.07.2007


So like he said my name's Preston Sandusky
from Kestrel Bikes.
And also I have John St. Denis also known
as JD, with me here.

I have quite a few slides, so I'm actually going to try to
go through them pretty quickly.
But my background, currently I'm the product and managing
director at Kestrel.
I started out as an engineering manager.
And I actually was President for awhile there before we
switched some ownership around.
So my basic background is mechanical engineer, US Air
Force, aerospace, carbon fiber stuff.

We're really happy to have the opportunity to come here
today, because Kestrel's a Northern California company.
And Kestrel made the first all carbon fiber bike in the world
on a production for sale basis.
And the technology and the engineering to do that came
out of the bay area and the Sacramento
area aerospace industry.

Back before companies like this were so prevalent here
aerospace was really huge down here.
And a lot of that early technology spun out of that.
So let me get started.
Like I said, I'm going to go through some of these pretty
fast. I just want to give a brief history of
when Kestrel started.
We already talked about it.
And then we'll talk a little bit about the materials
capabilities and why we use carbon fiber and then walk you
through the basic steps of the design and development cycle
on one of our products, or a couple of
our products, actually.
So like we've already said, Kestrel started in 1986 down
in Santa Cruz.
And what happened is the guys who had started Trek bicycles
about 10, 12 years prior to that got together with
aerospace carbon guys and decided to make a full carbon
fiber bike.
Prior to that there were bikes, bike frames, made with
carbon tubes, typically glued to aluminum legs, even steel
legs early on.
But at the time that Kestrel came out, carbon bike was
round carbon tubes bonded or glued to aluminum legs.
So it was very much metal bicycle technology with just
the tubes replaced by carbon.
So the first Kestrel was called the Model 4000.
Here it is here.
I keep looking at the screen, but it's actually
in front of my face.

And this bike revolutionized cycling in a
lot of ways, actually.
The obvious thing is it was the first full carbon fiber
composite molded bicycle frame.
But it also had things, like it was the first production
frame with aerodynamic tubing, and I'll talk a little bit
more about that when we get into it.
But the beauty of carbon fiber is its moldability.
And you can shape it however you want.
We try to shape in ways that make sense, but it's infinite
what you can do with carbon in a molded shape.

Once the first road bike came out we turned our attention to
mountain bikes and triathlon bikes.
In 1988 we came out with a full
suspension bike prototype.
And many people regard it as the bike that helped kick
start the full suspension craze that is now commonplace.
More people ride suspension bikes than the
non suspension now.

This is it, here, the Nitro show bike.
It was actually a collaboration.
For those of you who know some of the bike history or some of
the bike names, it was a collaboration with Kieth
Bontrager from Bontrager Cycles, Paul Turner, who ended
up starting Rock Shox, which, of course, in '88, '89 was
pioneering the suspension fork for mountain bikes.
And of course, Kestrel with the carbon fiber side.
We didn't end up making this bike.
We ended up making what we call a hard tail version,
which is actually a very similar design but without the
rear suspension.
Because the things like the breaks and the shocks didn't
actually exist in the market at the time.
This bike was pegged at about $6,000 in 1998
for a mountain bike.

Later on some of the other things we brought in that we
pioneered to the bike market, the EMS fork, or the carbon
fiber road bike fork, was a huge thing, came out in 1989.
And we also made the first all carbon triathlon bike.
So triathlon is a sport that's pretty big these days and
really growing fast, and at that time was
really in its infancy.
I think we were maybe the second company to make a
trigeometry specific production bike.
And the first one to apply carbon and aerodynamic tubing
to a triathlon or time trial bike for production.
We also came out this bike in about 1992.
This is a 500 SEI.
I think the photo is of the 500 EMS. The 500 SEI was its
And as you can see, it has no seat tube.

And this was a really good example of what carbon fiber
can do, not just for bicycles but in any structural design.
Because there's no way you're going to take steel or
aluminum or titanium metal bicycle frame material and
have any kind of efficient structure by
removing a tube like that.
And what this bike did, this is actually a road bike but it
was used by a lot of triathletes as well, as you
can see by the set up in this photo.
But what it really opened the door for was some aerodynamic
freedom with our triathlon bike designs.
And you'll see some more of that when I get
to the design process.

This is a lot of words here, but basically the materials
that we use to make frames come straight out of military
and aerospace industries.
It's called carbon fiber prepreg.
And prepreg means that the fibers are typically aligned
along an axis and then coated or treated with a matrix
material like epoxy resin.
So prepreg means preimpregnated, with, in our
case, the epoxy resin.
Literally we were specing, taking engineering materials
specs right out of aerospace and applying
them to these bikes.
In fact, probably the most important thing that Kestrel
pioneered back in the day was the marriage of real
engineering to the bicycle industry.
Prior to that, nothing against those engineers, but actually
a lot of the bike companies had engineering departments
that didn't have engineers, because it's mostly just
drawing tubes and mitering drawings to see what the tube
lengths are and how they come together to
be braised or welded.
So this was a very engineering intense project.
And I can tell you that joining Kestrel October '87
and going from the Air Force composites office in the
aerospace side and then watching them lay out the
whole bicycle frame in one piece with this material, it's
the kind of thing where a trained aerospace engineer
would just initially just say, you can't do that.
It doesn't work that.
Bicycle guys are pretty inventive guys.
You're talking about people like the Wright brothers.
So they're people that tend to have some ideas or some dreams
and go after it.
And not worry about what other people say
can or can't be done.
And I'm sure you folks here are familiar
with that as well.
So why carbon fiber?
The best thing about carbon fiber and a bike frame is the
stiffness to weight ratio.
Bicycle frames are what we call stiffness critical

As many of you know, you get on a bike and you don't want
it to be flopping and flexing around.
You want it to be stiff.
But it's a two dimensional structure.
The rear end is a little bit triangulated
in the third dimension.
That main frame and that main power transfer is done in a
two dimensional plane.
So stiffness becomes really the issue in a bike frame and
a lot of bike components.
Strength is too, but with metals you sometimes have the
condition where you have to design something around the
strength of the material rather than the stiffness.
With carbon, because the stiffness is so high, usually
once you have the stiffness under control the strength
almost comes along with it, with the design.
We do have to beef up areas for impact or certain really
high stressed areas in terms of strength
or structural testing.
But stiffness is the key, and carbon fiber composites far
outweigh metals.
And I have a little chart on that.

So here's the stiffness comparison.
Specific stiffness, I didn't really ask.
How many of you folks are engineers or material people?
Specific stiffness means stiffness to weight.
And you can see, I don't really have
a pointer, I think.

So you can see here, down here are the little blue bars.
These are these are the typical frame building metals,
steel, aluminum, titanium.
Those are the metals that were being used when
Kestrel came out.
And they're still the metals that are being
used in frames today.
Maybe not so much as it used to be, because carbon is
probably the dominant high performance material in bike
frames now.
But as you can see, those metals have actually different
stiffness properties and capabilities.
But when you factor in the density of the metals, their
stiffness to weight comes out very much the
same as each other.
And also a stiffness, it's pretty much regardless of the
alloy of the metal.

Strength varies more with the alloys, but stiffness to
weight is pretty much the same.
And then you can see, on the far side, the type of carbon
materials that we use.

I don't know if I can be here without being in the way or
off the camera.
This is the 700K material or our, quote unquote, "standard
material." And then the 800K here is our higher modulus
material, or what we use on our SL frames.

I don't know if you guys can quite read the numbers, but
you can tell from the graph that the specific stiffness of
carbon fiber that we use in the frames is about five to
seven times the stiffness to weight of
the metal frame material.
So from a pure engineering standpoint, if you don't have
a background in the traditional frame materials
and you just look at materials available, it's just really
obvious to use that carbon fiber composite materials are
the way to go.
The little red bars next to the carbon is actually the
carbon epoxy.

You can't build a bike just with carbon, the epoxy has to
hold it together.
So when you factor in about 35% or 40% epoxy, you still
have a stiffness to weight ratio of about three to four
times what the metals have. And actually more than that
with some of the newer fibers.

Strength to weight's the same thing.
There's a little more variance in the metal materials,
depending on the alloys, but they're heavy.
Carbon fiber epoxy, again as you can see, it has even
higher strength to weight than stiffness to weight.
And that's why I said if you make the frame stiff enough
the strength is almost always already there for you.
So again, the fibers themselves that we use, 11,
12, 13 times the strength to weight, or specific strength,
of metal materials.
And then the carbon epoxy blend still going to be six,
seven, eight times the strength to weight.

It's an engineer's dream.
A couple other things that weren't on the slide.

The main point there, I think is the big one, that carbon
fiber epoxy composites are fiber reinforced plastic.
So the epoxy matrix is surrounding all those fibers,
and it's plastic, basically.
So the shock damping capabilities of a carbon
composite material is 10 to 15 times the shock damping of
these traditional frame metals.
So imagine if you had a steel bell, an aluminum bell, and a
titanium bell.
They would all ring.
You'd hear them, they would ring.
You make a carbon epoxy bell and it's like hitting a
plastic bell, so it just doesn't ring.
What that allows us to do is separate the ride quality and
the damping of the frame or the structure from the
stiffness and the strength and the performance side of it.
So let's say you make a titanium frame.
You want it to be reasonably light and you want it to be
Well, if you make it very stiff it won't necessarily be
so comfortable.
If you make it comfortable, you're getting the
comfort out of flex.
Flex is bad in a bicycle frame.
So there's that balance with metals.
You try to balance it out, and I defy anybody to make a non
suspended frame out of metals that is as stiff as a carbon
frame and still has the kind of comfort you're looking for.
So with carbon fiber you make that structure, you say, I
want it this stiff.
It has to to pass these strength tests.

Blend or vary the fibers in the design according to weight
you're looking to get, and the shock damping is separate from
those properties.
So all of a sudden you have a super stiff bike like these up
here, the little one over there.
Very stiff, very, very efficient, and yet really
smooth frames.
Now, if you go up against a curb or something, it's a
stiff frame, you're going to feel it.
But that rough road buzz and smaller potholes and cracks
and things in the road, it just gets rid of those.
You don't get that bite through the handlebars and
that ringing in the frame.

So a couple general features, or general design approach in
pretty much all of our frames and products, using carbon.
And by the way, we only make carbon products.
The first one is modular monicot construction.

These are the solid models for the various sizes of that
frame, the Talon frame down at the end.
But way back when we used to try to mold these frames all
out of one piece, and it was great.
It worked great.
It was very complex, very expensive, and very, very much
less repeatable.

About 10 years ago or so we've gone to this modular monicot
And what that is taking all the best out of the carbon
fiber design, but breaking it up into not a lot of pieces,
but just a couple main structures.
For instance, the main frame here.
So that's a solid model that the mold or the
tooling is made from.
But it shows that the whole mainframe is
molded in one piece.
And then after the talk you folks can get a better look at
the bikes up here and you can actually see where, say the
seats stay in the assembly and the rear is one piece, and
then the chains in the assembly and
the rear is one piece.
And then they're all put in a bonding fixture and locked
permanently together.
The other thing that's a really big part of our design
work, and I think that carbon leaves you wide open to
opportunity, is in optimizing the tube shapes and the
junction design.

Somewhat doable in metals, but difficult.
Usually there's round tubes or near round tubes.
But in carbon, if you look at some of these designs, you'll
see that from one end of the tube to another can be a
completely different section.
It's all designed around the load conditions and the
structural requirements at any given point in the frame.

Also we can bring in aerodynamics, to see the
aerodynamic tube shape there in the down tube.
Maybe the down tube might flare out to the bottom
bracket to make it stiff there.
Some of the sections go from flat at the front, at the head
tube, the top tube on the top of the bike.
Up near the front, at the head tube, they might be more of a
horizontal section, and gradually morph
to a vertical section.
So it's infinite.
Anything you can put in the computer, which is pretty much
anything these days.
Didn't used to be.
Pretty much anything you put in there you can make with
carbon fiber.

The site specific structural design and fiber layup, again,
it's becoming the norm now in a bike
frame with carbon fiber.
Whereas with metals you might be able to use a thicker tube
or a bigger diameter tube as you went up in size.
But typically it was really hard to have a consistent
performance and consistent structural properties
throughout a size range of bikes.
But now we literally size every tube of the bike
proportional to the size of the frame.
And sometimes more than that.
Sometimes even wheel sizes and things are proportional to the
size of the frame.
But by sizing that tube it might look the same.
The general shape and design might be the same, but it's
just a little bit smaller or a little bit bigger for each
frame size.
And that means the 100 pound rider on the smallest frame
has the same kind of ride quality and feel and response
as the 250 pound rider on the largest frame.
And that's the goal there.
In addition to that, the carbon fiber layup itself, we
can put more or less layers of carbon fiber in a given tube
or tube junction to make the frame lighter or add material
to make it stiffer.
So we can tune it.

The bonding design and techniques, since Kestrel
started we've used aerospace grade structural adhesives.
This is not so much a point for this audience.
Some of our competitors use cheaper spec materials, like a
one part epoxy.
We use a two party epoxy.
They actually have to squirt it out in
production and mix it up.
But that's what gets the best results.
It has the higher strength, the higher sheer strength.
And it gives you the better quality and product.
The other thing that all our frames are going to have, the
ride tune stays and our EMS sport technology.
So like I said, we introduced the carbon fork to
the world in 1989.
And what we do now is every model of bike has its own
specific design fork.
So if you look at the image here you can see the mainframe
in blue and then you see the rear stays in the silver or
gray, as well as the forks.
So what we're able to do these days is to match the
performance and match the quality and design of the
front end to the rear end.
So you get a very balanced ride and a
very balanced feeling.
A repeatable performance our of the frame.

No compromise geometry, that's just something we do because
even though we're carbon fiber engineer guys we're a bicycle
company first. And so what we try to do is not cut corners
to make one size fits all frames.
It seems a silly thing to do in carbon,
because carbon's so light.
There's no reason to make a tube a little bit shorter to
make a frame a little bit lighter.
Get the geometry right, fit the rider correctly, and
design to that just as you would to weight or stiffness.
Let me grab a little sip here.

This picture is reminding me of some basics of what we do.
And now we have a couple frames that'll show you some
images, some examples of the actual design
process we go through.
One of them's the SRT 700, which is our
brand new road bike.
We have a couple of them up here you can check out after.
And then the other one is our real tri race specific bike,
it's called the Airfoil Pro.
It's very specific to triathlon racing.
It's not legal, actually, for any road racing
or time trial use.
But it's a very fast bike.
So I think I've covered most of these points.
We do all the design, all the engineering is done in our
Santa Cruz offices.
The frames are made overseas, like just about everybody is
these days.
We used to have a factory in Santa Cruz.

And like most bike companies that go overseas to get
carbon, we actually have experience and the engineers
who have set up factories in not only in the US, but in
other countries as well.
So we can go to those factories and we know how to
layup bikes.
And we know how to do the finishing work and all.
In fact, from the president of our company, who has set up
carbon bike manufacturing factories around the world,
and on down.

I talked a little bit, but just to reinforce that the
carbon is infinitely tunable.
So it comes in very thin sheets, and what we do, I
don't think I really showed this because I don't really
have the manufacturing so much as the design stages here.
So what you can do with the carbon, it's usually what we
call unidirectional carbon.
So the carbon's all going in one direction on the sheet and
then the sheets are cut to the different angles that we need
and we use different thickness of sheets that we need.
And then we stack those the sheets.
So say we need six layers in this big tube or we need five
layers in this smaller tube, or what have you.
The different number of layers, the angles, the
thickness, is along the tube or at the junctions.
All that's tailored to the particular design.

Everything we do now is 3D, solid model, CAD.
It didn't used to be.
When I started at Kestrel I was drawing center line
drawings by hand and working with industrial designers and
actually drawing it on paper.
And then the interesting thing, when we got into real
3D modeling, is that the software is
really capable now.
But about 10, 12 years ago when we first starting to do
it seriously, even say we use Pro Engineer software.
And we had designs that those guys couldn't model.
So we actually had to have customized software made to be
able to model the crazy compound curves and shapes
that we were doing.
But this is how the design cycle starts out.
We actually work with some very good industrial design
firms, usually local to the Santa Cruz area.
And we give them some definitions on what we're
looking for in a bike and start bouncing ideas around
and getting some sketches going.
This is the Airfoil Pro tri bike that I showed you.

Once that basic concept is done then we start getting
into the details.
OK, how is the cable routing going to work?
What's the seat binder going to look like?
So they'll get into these multiple iterations of these
types of sketches.
This one looks to be pretty far along in the process in
terms of the hand sketches.
And sometimes, by the way, they use computers for their
conceptual stuff or sketch type stuff.
That's a little cable port that came out of, probably, a
dozen concepts.
It's the one we zeroed in on the RT 700 bike.
Once we have the concepts done we'll start doing the solid
model CAD drawings.
I like this shot because, again, this
is the Airfoil Pro.
But what it shows is the solid part there is the main frame.
So the main frame design was pretty much
done at that stage.
And so now they're building the rear end onto the bike.
They're laying out all the clearances and trying to put
in the hard points, like the rear drop outs where the wheel
bolts in and where the brake bolts in.
And then a little further on, same frame.
This is a cool shot because you can actually see those
green and gray lines that are going down the main big tube
on the screen, the down tube, is actually some
of the cable routing.
So they're able to put in the anticipated thickness of the
carbon fiber wall and simulate the cable routing through the
frame, make sure there's no interferences.

Little hard to tell, but you can see some of the little
metal pieces that are bolted or riveted onto the frame that
guide the cables and things.
So we're actually able to put those into the CAD model and
make sure everything's good, functions properly, before we
go to CNC machine, a very expensive mold.
And by the way, all this stuff we do, if we make five or six
sizes of a frame, it has to be done for all the sizes.
Here you can see, this is the RT 700 model.
And obviously this is a fairly finished model.
But you can see some of those concept sketch pieces, like
the little gold cable guides, where they're actually fitting
them into place and designing the frame to be molded to
accept them.

Other one, that under the bottom
bracket cable guide piece.
This is a little injection molded thermoplastic piece.
And it went from that, I think, three piece concept
sketch down to this.

So basically there's little ports.

I don't know if you can see my point here.
So this port area is actually a hole through the frame and
the cables come out.
And then you can route them through the plastic piece.

Lost my marker again.
There it is.
And then it goes into these holes here to go up to front
derailer and rear derailer.

I'm not sure what this shot's for.
I just think it looked really cool so I
could put it in there.
It remind me of a Terminator Two liquid man.

But it was a rear drop route of the RT 700.
This is a problem.

We have a little power problem up here, I guess.
I should have turned my lighting down more.
So then, actually, a big part of it is checking all the
I think they're IGES files from Shimano, or whoever, and
actually put the components in and check all the fit and
I'm going to run out of power.

It might be pretty done anyway.
And then using the CAD model we can do some finite element
analysis depending on what the frame is and
what the needs are.
This bike doesn't have a seat tube, so it's kind of nice to
put some loads into it.
You can do the whole frame or you can do sections.
Sections are usually the better way to go.

| we can do with the CAD models before we commit to
tens or hundreds of thousands of dollars worth of machine
metal molds is, this is actually a CNC
machined piece of foam.
Actually several pieces of foam.
So they actually machined a frame out of solid foam,
assembled it together, we check it out.
Typically we change it.
We did change some design details on this.

There you go, thanks.
I can turn my lighting up here a little.
That used to be really expensive stuff to do.
And the prices on getting that stuff is going down like mad
these days.
And in fact this piece is actually done in house by the
industrial design firm we work with.

And then, boom, you have prototype.
Once you check everything out and make the mold we go to
prototyping phase.
And this is probably the first or second main
frame of the RT 700.
My cursor shows up, you can see the little port here.
That's actually the little metal port and that's actually
a stereolithography prototype part as well.
I don't know why my cursor disappears.
Back here you can see these little tabs
sticking out in the back.
That's where the stays in the rear is going to bond on.

JD, how's the time?

OK, thanks.
Another little prototype.
Not the prettiest picture, but this is raw,
right out of the mold.

There it is.
So this is an SLA part stereolithography.
Part, I don't know if you are familiar with how that works,
but that's basically where they have a plastic solution.
And they cross lasers to solidify it
and build this piece.
Not out of thin air but out of thin plastic, fluid.

They call it SLA, stereolithography.
Don't know what the A stands for.
Maybe it's a Canadian process, I'm not sure.
Stereolithography, eh?

And then you saw the mainframe.
This is a bonding fixture.
Part of the prototyping is figuring out that the tooling
and proofing it all out.
The bonding ficture's quite large in order to hold the
whole frame and bond everything into
alignment at one time.
And the nice thing about carbon is it
can't be bent or deformed.
So once it's bonded in alignment in the fixture it's
in alignment for life.
But that means you better do it right the first time.
So that's actually where the stays and the dropouts are
being bonded into the main frame on this fixture.
Not real fancy stuff, but it's effective.
And it's made for production speed.

Finally, once the basic prototyping is done we do a
whole battery of structural testing.

At Kestrel we pride ourselves on having really stringent
test requirements.
I know Pia was concerned with that on carbon fiber products.
And we actually agree, so the testing that we do is the kind
of stuff that was done on 1970s era heavy duty steel
bikes and 10 speed type frames.
So we surpass all the different government
requirements, whether it's US or Europe or Japan.
Our tests meet or beat all of those.

Of course, the test machine is vertically oriented, so it's
actually pushing the frame down to simulate a load at the
front wheel axle.
And it's like a frontal impact load.

It'll take, say 800 pounds and up to cause any kind of
structural damage to the frame in that way.

On some bikes, particularly the tri or the Aero bikes, we
also do wind tunnel testing from time to time.

This is that Airfoil Pro that we saw some of
the development images.
And it's being set up at the low speed wind
Tunnel down in San Diego.

This is our top pro triathlete.
His name is Chris McCormick.
He's actually quite a good triathlete.
He won about three or four triathlete of the year honors
for his 2006 accomplishments.
And one thing we did in 2006 was get him off his a more
conventional seat tubed bike onto this no seat tube, super
aero Airfoil Pro bike.
And what we found is that just the frame and fork, what we
call frame set, alone saved him about 100 grams of drag at
30 miles an hour.
Which is basically, if you rode 25 miles, or 40 km, in
one hour it would knock a minute off of that time, just
the drag savings there.
The other thing is that this bike is designed to put you in
a very aerodynamic position.
And the position change knocked another 100 grams of
drag, so another minute.

He can go way more than 25 five miles in an hour, but say
I was going 25 miles and in a 1 hour ride, now it would take
me 58 minutes.
Aerodynamics in triathlon and in pro cycling, especially the
time trial stages that I'm sure all you folks have seen
on TV and the internet.
The time trials are a pretty big catch word these days.
It's exciting to watch and the bikes are crazy and expensive.
So it really is important what you do aerodynamically.

The result, he was the best triathlete in
the world in 2006.
He won, I think, all but two races that he entered.
He got second place in those two.
And he really proved what we showed our development and in
our wind tunnel testing worked.
Ironman Hawaii, the big race of the year, he got second.
I think he was a minute and 11 seconds
behind the guy who won.
So one of the, I think, third closest
finishes in Ironman history.
We're looking for him to win the race this year.
But definitely what we did in the wind tunnel and his
positioning has helped him move up from sixth place a
couple years ago, second place last year, and bringing him
right down the neck to take first this year.
And that is the presentation.
We have a few minutes open for questions you folks may have.
Feel free to check out the bikes as well.
AUDIENCE: You might have
mentioned this in the beginning.
How many frames do you produce in a year?
PRESTON SANDUSKY: How many frames do we
produce in a year?
It's actually confidential information.
We're a small company.
We make bikes, now this year we make the bikes
from $1999 and up.
But we're very much a specialty manufacturer.

So it's really competitive, that information.
But we make in the range of a few thousand frames and bikes
a year, not tens of thousands.
AUDIENCE: So if carbon is so much stronger than traditional
metals, how come you don't see it in mountain bikes?
PRESTON SANDUSKY: I'm sorry, why don't we see mountain
bikes, did you say?
AUDIENCE: Yeah, [INAUDIBLE] carbon frame mountain bikes

PRESTON SANDUSKY: The question is why, if carbon's such a
strong, good material, why don't we see
more mountain bikes?
And I think the simple question is you are
going to see them.
More companies are using carbon for mountain bikes now.
And more companies that we're aware of are actually
heading that way.
So if I talk to a company that just makes mountain bikes I
say, dude, you have to go carbon.
If you don't do it somebody else is going
to beat you to it.
So it's actually a great material for mountain bikes.
But just like in road bikes where it took awhile for it to
gain acceptance, it's the same thing in mountain bikes.
And then maybe even more so because people are worried
about, people crash all the time, or they're worried about
rocks and things kicking up and hitting the frame.
We have made carbon mountain bikes since 1988, and I can
tell you that they're pretty bomber.

We tend to make them a little heavier and a little thicker
and tougher.
They've been very successful over the years.
But it's more of that acceptance thing.
Another thing is that when full suspension became really
prevalent, some of the benefits of the ride quality
of carbon aren't as noticeable, because you have
big, fat, soft tires and you have suspension.
So you just want it to be a super stiff structure because
suspension's giving you the comfort.
And you tend to don't want it to be too expensive.
So carbon fiber, the price is working down.
The design, the whole thing is coming that way.
And I think, just like if you watch the Tour de France now
and there's virtually no bikes that are made of metal in
there, whereas 10 years ago most of them were metal and 20
years ago all of them were metal.
I think you'll see that in mountain bikes.

AUDIENCE: What is the disadvantage of not having the
seat tube, other than that that it's not
legal for UCI races?
PRESTON SANDUSKY: Like why don't all bikes
not have seat tubes?
Well, you're right.
The biggest issue is UCI/USCF racing regulations.
A bike pretty much has to have a seat tube to be legal.
As a result that really limits what we can do design wise,
because we can make the triathlon bike specifically
for, and not care if it's UCI legal.
So we can do that and I wouldn't say target it to that
audience, but actually make it for that audience.
Make those people as fast as they can be.
But on a road bike or a bike for the general population,
the marking of that and what's accepted and what people are
looking for, it becomes very complex to go against that.
It makes a great ride.
I can tell you, if you have a road bike and it's designed
properly without a seat tube, like one of those first slides
I showed you, it's a phenomenally riding bike.
At the time that 500 series frames were made it was
actually the stiffest frame that we made in the bottom
bracket, but also the smoothest riding bikes.
We have to go with what the market wants, and definitely
the UCI rules do play into that.
In terms of the structural part, that frame also had
aerodynamics built into it, the aerodynamic tube shape.
So whenever you go for those kind of things you're going to
lose a little bit on the structural efficiency.
So I would say if you wanted to make the absolute lightest,
stiffest frame you're going to generally want a
triangulated frame.
But the frame I showed you there, that weiged 2.9 pounds
in 1992, 1994.
So you could get really close to two pounds, just like the
triangulated frames are now.
AUDIENCE: So let's say you have a carbon frame.

At what point do you look at the frame and say, I have this
nick or this gouge, or the neck's kind of damaged in
I need to get a new one.
PRESTON SANDUSKY: His question had to do with, basically, how
do you tell if there's any damage to the carbon frame,
how do you know?
And how do you know if it's bad enough to be a concern?
And that's another thing.
20 years ago, when Kestrel started, there was this whole
learning curve on all of that.
We felt we were teaching the industry, the bike shops, the
consumers about carbon fiber in general.
And then over time, obviously, we, and then more and more
people, have manufactured, have used it.
So it's come to be accepted.
And people have learned how to identify those things.
I would say that damage tolerance in a bike frame is
very dependent on the weight of the frame, not so much the
material of the frame.
So any time you're pushing that weight way down--
The way to make a bike frame light is to
make the walls thin.
And so when you start doing that it's going to become less
damage tolerant, no matter what you do.
And so with carbon, we've actually seen things where in,
say a criterion race, and people have gone down and five
guys crash in a pile up.
They get up, three of them have steel or aluminum frame
that's bent and they can't keep riding, but the guy on
the Kestrel or the carbon frame could.
So what I see in carbon is when it gets generally slammed
it's really good, because it doesn't bend.
But it is different than metal for localized impact,
especially sharp stuff.
Not so much the big stuff, because metal tubes dent, too.

They're damaged by the same kind of things, but the damage
is different.
So to answer your question, usually you'd take it to the
bike shop that's qualified to look at it, and/or send it to
the manufacturer.
We'll get people, I crashed.
And they'll send us a digital photo of some damage where the
handle bar came around and smacked the tube or something.
Start from there.
I think that's about all the time we have. Thanks a lot for
coming and for the opportunity.