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Trek Madone rear brake cable friction problem - Help

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Trek Madone rear brake cable friction problem - Help

Old 08-08-13, 10:00 AM
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teterider
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Trek Madone rear brake cable friction problem - Help

I'm working on a Trek Madone, 2009 or so with semi-integrated post and internal routing with rear brake cable exiting top of top tube.

Running the cable is no problem, but there is so much friction coming from the front internal housing stop (or so it seems) that the brake can't retract the lever. I believe I've isolated here by just pulling on the bare cable as it exits the frame and it takes significant force to pull the cable back through and retract the brake lever. It is smooth as silk in the housing before entering the frame so the culprit really looks like the front stop which of course if riveted into the frame. I tried both the new Shimano cable and a new plus thinner Jagwire Pro Road cable.

This is a used frame the customer got a swap meet to build with Ultegra 6700. So what am I missing here to smooth this out?

Thanks for the help.
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Old 08-08-13, 10:13 AM
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reptilezs
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new housing? is the frame the aero style seat mast or the newer round style? post a pic of the setup. i work at a trek dealer and the brake housing stop has never really been an issue. i would make sure the stop is free and clean of corrosion. running a small drill bit through by hand should be a easy check. i have had issues with corroded stops on brakes themselves
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Old 08-08-13, 10:16 AM
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Check the housing itself and make sure that you didn't curl the end of the coil in toward the center. Also check that it's cut square, and that the ferrule fits snugly. Otherwise the housing can cam to one side when the cable is tensioned causing binding or the running wire.

If you suspect the fitting itself push a spoke through and make sure there's no obstruction.
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Old 08-08-13, 11:51 AM
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OK, problem solved.

So yes the housing was brand new with the 6700 shifters. I was using the very clean factory cut end in the frame, but cut a new end anyway to try that - although not the problem.

The cable fed into the front stop no problem but was really getting hung up on something as it slid back and forth through the frame. My inclination was a groove had formed somewhere on the guide and the cable was pinching in a groove causing the friction. (this is a used frame and could have 20k miles on it for all I know)
What I did was shined a bright light into the front cable stop and saw what in fact appeared to be a groove and a couple ways the cable could go. I then shined the light into the frame from the rear access hole, and guided the cable to bypass this groove

Obviously this is a very small hole to look into and really make out what is going on in there, but it seems there were 2 ways the cable could go and one way, which is where the cable naturally wanted go just by threading it in, had a worn groove that was causing the friction.

Well hopefully this helps someone else now that it is the forum record.

Last edited by teterider; 08-09-13 at 08:55 AM.
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