carbon fork dropouts

Ted wrote:
Okay, now I am worried. How tightly do I crank up my QR? I don't want
the axle to move with the torque but I also don't want to crush my drop
out.
Ted.

quit worrying. the carbon is tremendously strong. unless you abrade it
by frequent removal/reinsertion, /and/ use an old style hub with sharp
serrations vs. modern shimano with curved serration faces or smooth
faces like campy record, there's no problem. and you also have the
lawyer lips to prevent disaster even if you don't close the qr.

Eric Shanabrook wrote:

Are there any fork carbon-dropout durability issues, it seems like metal
might be a better material...for the dropouts? Could Carbon fiber
crumble/crush under compression over time (compression from the skewer),
but the fork makers probably have it figured out ok.
I spoke to my french mechanic about it, who was a TdF mechanic for a long
time. He now sells Colnago and he told me that Colnago used to have 100%
carbon forks, but they went back to metal dropouts because of durability
issues......


Greets, Derk

On Fri, 06 Jan 2006 00:40:09 -0800, cel wrote:

The forks don't see much torque on a road bike with rim brakes under normal
conditions. I guess if you can put lateral loads on the front wheel then may
need to be tighter. You don't need to tighten them as much as the rear
wheel, especially horizontal dropouts. I would go tight enough so that if
you bang on the top of the wheels with your fist the wheel doesn't budge.

I disagree. I once ruined a fork, since my Q/R was only "tight enough".
I had a crash with another rider, and my wheel came out of the fork. Then
the fork end dug into the pavement and bent 90 degrees.

Since then my front Q/R is as tight as I can make it and still have it
removable.

--

David L. Johnson

__o | "A foolish consistency is the hobgoblin of little minds, adored
_`\(,_ | by little statesmen and philosophers and divines." --Ralph Waldo
(_)/ (_) | Emerson

jim beam wrote:

quit worrying. the carbon is tremendously strong.

The carbon is only strong in the direction the fibers are aligned.
Unless there are fibers oriented *across* the dropout, parallel to the
hub axle, what you have is a plastic dropout for clamping purposes.

I confirmed this with the composite structures specialist at the
aerospace company where I work. When I told him that the clamping
pressures in a QR were on the order of 2000 lbs., he said, "that might
not be a problem." However, it's clear that local clamping pressures
are higher than that with a knurled QR nut.

How compatible could such a fork be with nutted axles? My best guess
is not at all.

CFRP fork ends are just a plain bad idea.

Chalo Colina

Ted wrote:
Okay, now I am worried. How tightly do I crank up my QR? I don't want
the axle to move with the torque but I also don't want to crush my drop
out.

One of our vendors writes in the owner's manual that the
lever should leave an imprint on your palm for a few seconds.
If there are no other issues (axle too long, frame ends out
of plane, etc) and if the cam is lubricated I think that's a
good standard.

An imprint for a few seconds is not a purple bruise either.
--
Andrew Muzi
www.yellowjersey.org
Open every day since 1 April, 1971

Derk wrote:
....He now sells Colnago and he told me that Colnago used to have 100%
carbon forks....

Diamond fork?

--
Tom Sherman - Fox River Valley

David,

That a good point I didn't think of. However you were going to crash anyway.
So if we assume that carbon dropouts cannot take large clamping forces (I
suspect lower than steel or aluminium) then you are left with the choice of
damaging the dropouts from clamping too tightly, or only damaging the forks
in a crash. I would take the later. If you are concerned about the cost of
replacing a fork, or the carbon dropout you shouldn't buy a fork like this
anyway.

cel


"David L. Johnson" wrote in message
news
On Fri, 06 Jan 2006 00:40:09 -0800, cel wrote:

The forks don't see much torque on a road bike with rim brakes under
normal
conditions. I guess if you can put lateral loads on the front wheel then
may
need to be tighter. You don't need to tighten them as much as the rear
wheel, especially horizontal dropouts. I would go tight enough so that
if
you bang on the top of the wheels with your fist the wheel doesn't
budge.

I disagree. I once ruined a fork, since my Q/R was only "tight enough".
I had a crash with another rider, and my wheel came out of the fork. Then
the fork end dug into the pavement and bent 90 degrees.

Since then my front Q/R is as tight as I can make it and still have it
removable.

--

David L. Johnson

__o | "A foolish consistency is the hobgoblin of little minds, adored
_`\(,_ | by little statesmen and philosophers and divines." --Ralph
Waldo
(_)/ (_) | Emerson

On Fri, 06 Jan 2006 23:16:54 -0800, cel wrote:

David,

That a good point I didn't think of. However you were going to crash anyway.
So if we assume that carbon dropouts cannot take large clamping forces (I
suspect lower than steel or aluminium) then you are left with the choice of
damaging the dropouts from clamping too tightly, or only damaging the forks
in a crash. I would take the later. If you are concerned about the cost of
replacing a fork, or the carbon dropout you shouldn't buy a fork like this
anyway.

It's not just the cost of replacing a fork. You want the wheel to stay on
the fork in a crash. A wheel can provide some energy dissipation in case
of contact with large fixed objects. Better your wheel than your bod.

But this really does boil down to another argument against carbon fork
ends.


--

David L. Johnson

__o | "What am I on? I'm on my bike, six hours a day, busting my ass.
_`\(,_ | What are you on?" --Lance Armstrong
(_)/ (_) |

On 6 Jan 2006 12:09:35 -0800, "Chalo" wrote:


How compatible could such a fork be with nutted axles? My best guess
is not at all.

Yeah, that's sure to a drawback for many users....

JT

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Johnny Sunset wrote:


Derk wrote:
....He now sells Colnago and he told me that Colnago used to have 100%
carbon forks....
It should be, considering the price of the Star fork. :-)

I meant their forks had carbon dropouts, but according to that mechanic,
they stopped production because of problems with the carbon dropouts.

Greets, Derk