CHOOSING A FORK

Chalo said:

jim beam said:

1. it's not "recommended" of course, but helo blades have been known to
survive multiple complete penetrations, not just surface damage.

The ones that come back, you mean. The others tell no tales.

eh? like aluminum blades have a better record???

Quoted message said:

I remind
you that you are comparing a solid slab of material as big as a floor
joist to a thin-walled hollow shell structure as thick as your thumb.
I don't think you can draw sound comparions, but if you wanted to try,
you'd best include the rotors that disintegrated on being hit and never
made it home.

massively mixed metaphors there guy. the whole point is that much to
everyone's surprise, composites /are/ often found to make it home. and
sometimes, after having sustained /more/ damage than is seen in metal
survivors. that's not to say composites are indestructible, but they
can and do take a beating.

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Quoted message said:

2. planes /are/ going composite. check out the next gen boeing designs.
and of course, airbus has been using composites for how long already?

Neither of them are using composites where they can make contact with
solid objects.

so? nor is aluminum!

? Heard of Glare?

yes. it's a glass fiber composite.

Quoted message said:

If so, did you wonder why they'd skin
a composite with metal?

and how do glass fiber surface defects react to air/moisture?

Quoted message said:

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3. combat helmets are composites because they're tougher, stronger,
lighter. like a fork needs to be.

Whatever, man. The median mechanical load on them is cinching up the
chinstrap, and once they see a peak load, they get replaced or given to
the next-of-kin.

dude, first, if you think that's the only time a helmet takes a knock,
you've never worn one. second, if you think a steel helmet's much use
when directly hit by 7.62mm, your n.o.k. might be disappointed.
composite helmets otoh, /do/ protect against the above, and very
effectively. i once met a guy who got hit on the [composite] helmet by
a sniper in bosnia. he was quite delighted with its performance.

Quoted message said:

Quoted message said:

and please don't lecture me on materials theory chalo - stick to what
you actually know.

You know what you know; I make my living building aircraft and
spacecraft. I designed a tooling process for machining and fastening
to honeycomb core glass/epoxy panel last week, and I'll be using it to
make flight article week after next. These days I'm also doing a lot
of troubleshooting of attaching things made of good old reliable
aluminum to things made of not-so-reliable carbon/aramid sandwich. I
know plenty enough about advanced composites to know why *I* don't
consider them a good idea for most folks' bikes. If you spent much
time cutting and clamping and fastening things made out of CFRP, then
you'd probably not want it on your bike either. It's fussy and
unforgiving, and once damaged it's trash.

two things:
1. re-read what i said. i'm not saying you know nothing; i'm asking you
to stop trying to b.s. me about materials theory like the behavior of
"glass and amorphous silicon".
2. you're comparing apples to oranges. trying to imply honeycomb is
inappropriate for forks would be true, but it's not because it's a
composite. ti honeycomb would be inappropriate for forks too - it's
simply the wrong morphology.

Quoted message said:

Chalo Colina

John Forrest Tomlinson said:

The thing is, in this group there are a bunch of people who talk about
risks that are so extremely rare as to be almost incalcuable, as if
they are tangible, simply because they involve something "fancy" that
they don't like. Steel steerer tubes fail too -- but because they're
perceived as heavy and old-fashioned so we don't hear as many warnings
about that. It's an irrational set of scare mongering aimed at things
that are "new" or "fancy."

I've seen 700g steel forks fail from manufacturing defects, but i've
yet to see a 450g carbon fork fail. i'm sure there have been carbon
fork failures, but i agree, just because it's steel and it's heavy
doesn't mean it will be strong. almost all the frame failues i've seen
have been steel frames, lugged and tigged.

Peter Cole said:

dvt wrote:

Quoted message said:

Quoted message said:

Peter Cole wrote:

Quoted message said:

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Impact strength is not much of an issue anywhere on a bike except for
the fork.

Quoted message said:

Quoted message said:

I dunno about that... I've seen plenty of dented top tubes in my day. I
even dented one myself. All were steel or aluminum bikes, and all saw
many miles of use with the dents. I can't say what would have happened
if they had CF top tubes instead.

Quoted message said:

What I meant was not that impacts were less likely to cause failure, but
that frame tube failures are generally not as dangerous as fork failures.

This is true.

The real problem with carbon forks is, there's no sure way to inspect
them for damage. A damaged steel or aluminum fork is either bent or
cracked, while a carbon one may have fatal internal cracks that can't be
seen or otherwise detected. Therefore a carbon fork involved in a crash
should be retired. As they say in the kitchen, "When in doubt, throw it
out!"

With this in mind though, there's no reason to worry about riding carbon
forks. Stick with reputable brands though.

Matt O.

John Forrest Tomlinson said:

On 19 Mar 2006 07:57:52 -0800, "Ozark Bicycle"
<[email hidden]> wrote:

Quoted message said:

Quoted message said:

IOW, think long and hard about how much risk you are willing to take
for the sake of saving 8-12oz.

Quoted message said:

How much risk it it? I'm certain that carbon forks from a good
manufactuer nowadays are as safe as steel forks of about 20 years ago.
I've seen at least one broken steel steerer tube (which *caused* a
crash), for example, but never seen a carbon fork fail except as the
result of a crash.

I agree. The quality control for carbon forks now is far better than it
was for many steel forks years ago. Remember Lotus? Lambert?

Matt O.

Matt O'Toole said:

Peter Cole said:

dvt wrote:

Quoted message said:

Quoted message said:

Peter Cole wrote:

Quoted message said:

Quoted message said:

> Impact strength is not much of an issue anywhere on a bike except for
> the fork.

Quoted message said:

Quoted message said:

I dunno about that... I've seen plenty of dented top tubes in my day. I
even dented one myself. All were steel or aluminum bikes, and all saw
many miles of use with the dents. I can't say what would have happened
if they had CF top tubes instead.

Quoted message said:

What I meant was not that impacts were less likely to cause failure, but
that frame tube failures are generally not as dangerous as fork failures.

This is true.

The real problem with carbon forks is, there's no sure way to inspect
them for damage. A damaged steel or aluminum fork is either bent or
cracked, while a carbon one may have fatal internal cracks that can't be
seen or otherwise detected. Therefore a carbon fork involved in a crash
should be retired. As they say in the kitchen, "When in doubt, throw it
out!"

Exactly. With a steel fork, apres crash, if the blades and dropouts are
still aligned, you know you are probably good to go. With CF, there's
no way to be sure. That's not a problem in the kitchen of sponsored
teams where replacement is routine, but recreational riders might be
oblivious to the hidden damage.

Quoted message said:

With this in mind though, there's no reason to worry about riding carbon
forks. Stick with reputable brands though.

Absolutely agreed, aside from hidden impact/crash damage and the hidden
effects of abrasion/nick damage, most CF forks are strong and safe.

Squid-in-Training said:

Are you saying spontaneous failure? Have you ever heard of anyone's carbon
fork breaking JRA (either post-crash or not)? I'm curious to see if we can
compile some statistics...

I haven't, but as I alluded to already there have been plenty of steel
ones. My sister was a Lotus victim, fortunately not hurt. These failures
were widespread and well known. I'm sure some of the
shopkeepers/mechanics here who have been around that long would concur.

Matt O.

Matt O'Toole said:

The real problem with carbon forks is, there's no sure way to inspect
them for damage. A damaged steel or aluminum fork is either bent or
cracked, while a carbon one may have fatal internal cracks that can't be
seen or otherwise detected.

Internal cracks with nothing on the surface? How does that happen?
Are shock waves transmitted into teh middle of the fork somehow. Or
does the fork bend and become "injured" inside, like a broken bone in
the human body?

Quoted message said:

Therefore a carbon fork involved in a crash
should be retired.

I know dozens of people playing with fire right now then.

JT

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Matt O'Toole said:

Peter Cole said:

dvt wrote:

Quoted message said:

Quoted message said:

Peter Cole wrote:

Quoted message said:

Quoted message said:

>Impact strength is not much of an issue anywhere on a bike except for
>the fork.

Quoted message said:

Quoted message said:

I dunno about that... I've seen plenty of dented top tubes in my day. I
even dented one myself. All were steel or aluminum bikes, and all saw
many miles of use with the dents. I can't say what would have happened
if they had CF top tubes instead.

Quoted message said:

What I meant was not that impacts were less likely to cause failure, but
that frame tube failures are generally not as dangerous as fork failures.

This is true.

The real problem with carbon forks is, there's no sure way to inspect
them for damage. A damaged steel or aluminum fork is either bent or
cracked, while a carbon one may have fatal internal cracks that can't be
seen or otherwise detected. Therefore a carbon fork involved in a crash
should be retired. As they say in the kitchen, "When in doubt, throw it
out!"

it's really not accurate to say that a steel or aluminum or steel fork
will have cracks that are visible. sometimes they are, sometimes,
they're not. carbon can have cracks that are visible, not visible, but
almost always audible.

Quoted message said:

With this in mind though, there's no reason to worry about riding carbon
forks. Stick with reputable brands though.

Matt O.

Andrew Lee said:

John Forrest Tomlinson said:

Ozark Bicycle said:

impact damage to CF can be, in effect, invisible for a time. Then,
it manifests in a break. This isn't news.

Just because people say something doesn't make it likely.

It wasn't with a fork, but I've had this happen with a carbon fiber ski
pole. I had likely fallen on the pole earlier in it's life - the
uncertainty coming from whether it was the same pole that I had fallen on,
but there were probably at least two falls where I ended up on the poles
(without bending them too much, I had thought). When the pole finally
failed, it was while I was just skiing along. No fall, no crash, no one
skied over it, etc. There must have been a year or two between the last
fall on the pole and the failure. There was no outward indication that the
pole was about to fail. I used those poles every other day for about 5
months a year, so there was a lot of normal use between crash and failure.

Back in the late eighties, I had a Basso Gap steel frame that I really
loved. The front hub on my training wheels was a Maillard that must
have been warped or something. Gradually the cones would loosen up and
eventually the front wheel would get kind of wobbly. Once a month or so
I would have to tighten up the front bearings. I was in college, didn't
have a lot of money, so I just lived with it.

I went out for a sixty mile ride one day and about halfway through I
noticed that my front rim was moving back and forth quite a bit when I
would pedal out of the saddle, more so that usual when the front hub
loosened up. When I got home I decided to have a look, something really
seemed wrong, so I undid the front quick release and...

The right fork leg fell down on the driveway. The fork crown had
cracked in half. So steel can also fail without any warning. I didn't
slam into any big potholes or anything like that on the ride. I knew
someone else who had the same problem with a Basso, so they must have
had a batch of defective forks about this time.

Maybe there wasn't any outward sign of failure in your ski pole, but I
didn't notice the crack in my fork crown, but I'm sure it had been there
for a while.

-Eric

In article
<[email hidden]>,

E Goforth said:

Andrew Lee said:

John Forrest Tomlinson said:

On 19 Mar 2006 15:11:14 -0800, "Ozark Bicycle"
<[email hidden]> wrote:

> impact damage to CF can be, in effect, invisible for a time. Then,
> it manifests in a break. This isn't news.
Just because people say something doesn't make it likely.

It wasn't with a fork, but I've had this happen with a carbon fiber ski
pole. I had likely fallen on the pole earlier in it's life - the
uncertainty coming from whether it was the same pole that I had fallen on,
but there were probably at least two falls where I ended up on the poles
(without bending them too much, I had thought). When the pole finally
failed, it was while I was just skiing along. No fall, no crash, no one
skied over it, etc. There must have been a year or two between the last
fall on the pole and the failure. There was no outward indication that the
pole was about to fail. I used those poles every other day for about 5
months a year, so there was a lot of normal use between crash and failure.

Back in the late eighties, I had a Basso Gap steel frame that I really
loved. The front hub on my training wheels was a Maillard that must
have been warped or something. Gradually the cones would loosen up and
eventually the front wheel would get kind of wobbly. Once a month or so
I would have to tighten up the front bearings. I was in college, didn't
have a lot of money, so I just lived with it.

I went out for a sixty mile ride one day and about halfway through I
noticed that my front rim was moving back and forth quite a bit when I
would pedal out of the saddle, more so that usual when the front hub
loosened up. When I got home I decided to have a look, something really
seemed wrong, so I undid the front quick release and...

The right fork leg fell down on the driveway. The fork crown had
cracked in half. So steel can also fail without any warning.

You had warning. I expect that today you would respond to
that kind of symptom by dismounting and executing a
thorough check of the bicycle.

Quoted message said:

I didn't
slam into any big potholes or anything like that on the ride. I knew
someone else who had the same problem with a Basso, so they must have
had a batch of defective forks about this time.

Maybe there wasn't any outward sign of failure in your ski pole, but I
didn't notice the crack in my fork crown, but I'm sure it had been there
for a while.

-Eric

--
Michael Press

Quoting E Goforth <[email hidden]>:

Quoted message said:

I went out for a sixty mile ride one day and about halfway through I
noticed that my front rim was moving back and forth quite a bit when I
would pedal out of the saddle, more so that usual when the front hub
loosened up. When I got home I decided to have a look, something really
seemed wrong, so I undid the front quick release and...
The right fork leg fell down on the driveway. The fork crown had
cracked in half. So steel can also fail without any warning.

It sounds to me like you had at least 30 miles warning before any critical
failure.
--
David Damerell <[email hidden]> Kill the tomato!
Today is Second Brieday, March.

I have. And the family of the deceased is suing Trek and the LBS over the
spontaneous failure. Here's a link to the St. Petersburg Times article.
http://pqasb.pqarchiver.com/sptimes/927273851.html?MAC=b472465510e08377863fdbbd425a4b50&did=927273851&FMT=FT&FMTS=FT&date=Nov+16%2C+2005&author=LORRI+HELFAND&pub=St.+Petersburg+Times&printformat=&desc=Veteran+cyclist+dies+after+trail+fall

If it doesn't work for you, go to www.sptimes.com, at the top right choose
to search "archives" for "cyclist dies". It'll be the third article.
Incidently, he was not a careless, "it'll never happen to me", 20-something
hot-dog. He was a 69 year old veteran cyclist.

Now. All that having been said, my wife and I both ride cf forks, and I'm
seriously considering putting a Woundup fork on our tandem.

--
Bill & Maggi
05 Trek T2000
Clearwater, Fl.

"Matt O'Toole" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

Squid-in-Training said:

Are you saying spontaneous failure? Have you ever heard of anyone's
carbon
fork breaking JRA (either post-crash or not)? I'm curious to see if we
can
compile some statistics...

I haven't, but as I alluded to already there have been plenty of steel
ones. My sister was a Lotus victim, fortunately not hurt. These failures
were widespread and well known. I'm sure some of the
shopkeepers/mechanics here who have been around that long would concur.

Matt O.