CHOOSING A FORK

[jim beam]

Chalo wrote:
> jim beam wrote:
>
>>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???

> 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.

>
>
>>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.

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

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

>
>
>>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.

>
>
>>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.

>
> Chalo Colina
>

 

[[email protected]]

John Forrest Tomlinson wrote:

> 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.

 

[Matt O'Toole]

On Mon, 20 Mar 2006 06:58:44 -0500, Peter Cole wrote:

> dvt wrote:

>> Peter Cole wrote:

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

>> 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.

> 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.

 

[Matt O'Toole]

On Sun, 19 Mar 2006 12:11:11 -0500, John Forrest Tomlinson wrote:

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

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

> 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.

 

[Ozark Bicycle]

Matt O'Toole wrote:
> On Mon, 20 Mar 2006 06:58:44 -0500, Peter Cole wrote:
>
> > dvt wrote:
>
> >> Peter Cole wrote:
>
> >>> Impact strength is not much of an issue anywhere on a bike except for
> >>> the fork.
>
> >> 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.
>
> > 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.


> 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.

 

[Matt O'Toole]

On Sun, 19 Mar 2006 23:53:09 -0500, Phil, Squid-in-Training wrote:

> 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.

 

[John Forrest Tomlinson]

On Tue, 21 Mar 2006 15:02:22 -0500, Matt O'Toole
<[email protected]> wrote:


>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?

>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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[jim beam]

Matt O'Toole wrote:
> On Mon, 20 Mar 2006 06:58:44 -0500, Peter Cole wrote:
>
>
>>dvt wrote:
>
>
>>>Peter Cole wrote:
>
>
>>>>Impact strength is not much of an issue anywhere on a bike except for
>>>>the fork.
>
>
>>>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.
>
>
>
>>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.

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

 

[E Goforth]

Andrew Lee wrote:
> John Forrest Tomlinson wrote:
>> On 19 Mar 2006 15:11:14 -0800, "Ozark Bicycle"
>> <[email protected]> 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. 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]

In article
<[email protected]>,
E Goforth <[email protected]> wrote:

> Andrew Lee wrote:
> > John Forrest Tomlinson wrote:
> >> On 19 Mar 2006 15:11:14 -0800, "Ozark Bicycle"
> >> <[email protected]> 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.

> 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

 

[David Damerell]

Quoting E Goforth <[email protected]>:
>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 protected]> Kill the tomato!
Today is Second Brieday, March.

 

[Onegun]

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...t=&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 protected]> wrote in message
news[email protected]...
> On Sun, 19 Mar 2006 23:53:09 -0500, Phil, Squid-in-Training wrote:
>
>> 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.
>