Carbon frame with internal cable routing, wear at ingress/egress points?

[Doug]

I'm building up a roadie on a monocoque carbon frame that has internal
shift cable routing. At the points where the cables enter the frame
near the cable stops, and at the point where the cable leaves the
frame near the front der, the cable does not enter/exit perfectly
centered in the hole. It rubs on the frame, due to the entry/exit
angle.

Long term, do I have to worry about wearing a groove in the entry/exit
holes? What can be done if so? I presume the rubbing of the cable
along the entire length on the internal tunnel is not a problem since
that bearing surface is so large. But right at the entry/exit holes,
the rub point is concentrated.

The rear der exit hole is OK. There is a little aluminum cable end
piece that comes with Ultegra brifters that fits perfectly in the hole
and prevents the exit hole rub point. That hole also has a molded cup
in the frame to accept such a cable end piece. The other holes don't.

Doug

 

[dianne_1234]

On Sun, 17 Oct 2004 16:30:59 GMT, Doug
<[email protected]> wrote:

>I'm building up a roadie on a monocoque carbon frame that has internal
>shift cable routing. At the points where the cables enter the frame
>near the cable stops, and at the point where the cable leaves the
>frame near the front der, the cable does not enter/exit perfectly
>centered in the hole. It rubs on the frame, due to the entry/exit
>angle.
>
>Long term, do I have to worry about wearing a groove in the entry/exit
>holes? What can be done if so? I presume the rubbing of the cable
>along the entire length on the internal tunnel is not a problem since
>that bearing surface is so large. But right at the entry/exit holes,
>the rub point is concentrated.
>
>The rear der exit hole is OK. There is a little aluminum cable end
>piece that comes with Ultegra brifters that fits perfectly in the hole
>and prevents the exit hole rub point. That hole also has a molded cup
>in the frame to accept such a cable end piece. The other holes don't.
>
>Doug

What kind of frame is it?

FWIW I've seen Kestrels with severe wear at the cable entry/exit
points and no problems from it. It's like the cable over long use is
sawing into the carbon. I've considered smoothing out or slightly
widening the wear groove so the cable doesn't bind, but it's never
gotten bad enough to make me actually try it. ;-).

If some Teflon liner fits into the holes, maybe you could install some
to slow the rate of wear.

 

[Doug]

>>At the points where the cables enter the frame
>>near the cable stops, and at the point where the cable leaves the
>>frame near the front der, the cable does not enter/exit perfectly
>>centered in the hole. It rubs on the frame, due to the entry/exit
>>angle.
>
>What kind of frame is it?

I'm trying to figure that out. It's from a Taiwan factory (I think)
with some odd dimensions. 1 inch steerer and 25.4 seatpost. BB is
68. It does not have a straight downtube. It's curved a bit. Same
for the top tube. The seat tube is not entirely tubular. It has a
sort of aero profile. The seatstays are wishbone, the chainstays
conventional. Finish is painted black. Weight is 2.7 roughly for a
53 c-c with 55 c-c top tube.

>FWIW I've seen Kestrels with severe wear at the cable entry/exit
>points and no problems from it. It's like the cable over long use is
>sawing into the carbon.

Precisely what I feared.

A wrench in an LBS saw it and thought it was a Kestrel. I've been
checking pics of Kestrels to see if this is one of theirs.

>If some Teflon liner fits into the holes, maybe you could install some
>to slow the rate of wear.

Now the question where to find something like that. I'll poke through
the hardware store and Home Depot. Any ideas for a particular
application where such liners are used?

Doug