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Old 06-12-10, 11:33 PM   #1
DRietz
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Lots of Friction in Rear Brake Cable

Hey all you mechanics. I seem to be having quite an issue with the latest additions to my project.

I routed up the rear brake cable today (mid-80's Nishiki, so along the TT) and it seems that there's a lot of friction in the set up. If I press down on the lever and just release my hand, there's a slight delay in the cable being pulled back to its resting position. If I snap the brake lever, then there is no delay.

It's a DiaCompe aero lever with the old, specialized ferrule. The rear brake is modern-ish Campy Veloce, and the housing is unlined and thus the brake cable was greased prior to installation.

So...why am I having issues? As far as I can tell, I cut the ends square and there are no issues with the cable itself...
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Old 06-12-10, 11:53 PM   #2
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too much grease maybe?
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Old 06-12-10, 11:56 PM   #3
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Could be a possibility. Solutions?
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Old 06-13-10, 01:12 AM   #4
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You don't want actual grease in that long a run. It acts too much like a viscous shock absorber and slows down the cable movement just as you've found. Oil is the way to go. And it doesn't take much of it either. A light coat of oil will provide a nice snappy feel compared to greasing the cable. Clean it out and try the oil. Or better yet spring for some new lined housing and a stainless smooth drawn cable.
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Old 06-13-10, 03:46 AM   #5
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Make sure the housing was cut cleanly and that there's no burr pushing in on the cable. I file or grind mine flat then open the liner with an awl before sliding the ferrule on.
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Old 06-13-10, 10:55 AM   #6
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BCRider...if I already put grease on the cable and it went through the housing, what's the best way to clean it out? I know it's better to use lined housing, but I am seriously on that much of a budget right now.
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Old 06-13-10, 11:02 AM   #7
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WD-40 shot into the cable housing should mix and dilute the grease well enough.

simply wiping the cable with a rag should clean off quite a bit of grease as well.
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Old 06-13-10, 11:09 AM   #8
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The WD-40 won't gunk up in the housing itself then?
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Old 06-13-10, 11:13 AM   #9
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The WD-40 won't gunk up in the housing itself then?
The oil left by wd-40 is pretty light... don't squirt yourself in the eye.
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Old 06-13-10, 11:19 AM   #10
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I never grease rear brake cables, just coat 'em with a film of TriFlow. Dribble a little on and spread it around with thumb and fore finger.

At this point I wouldn't worry so much about it. Your braking performance won't be hampered by a slow return and if your wheels are true you won't be slowed much if brake return takes a second instead of a half second. I'd go ahead and wipe excess grease of, however.
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Old 06-13-10, 08:07 PM   #11
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WD as mentioned already would do nicely. Squirt it in and let sit for 30 minutes to dissolve the grease then squirt through some more to blast out the muck. Wipe off the cable with WD as well.

The very light anti rust oil left by the WD is just right for lubing a brake cable of this sort. So just let the excess drain after the second blast out and put everything back together.
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Old 06-14-10, 04:01 AM   #12
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Make sure you separate cable-friction from caliper-friction. Disconnect the cable from the rear-brake and pull on the inner-wire and alternate between pulling it versus squeezing the brake-lever (flossing the inner-cable back and forth). Due to the length of the cable-run, housing-compression and friction, you can never get the rear-brake as crisp as the front.

A lot of calipers have adjustable spring-preload. I typically set the front-brake to low-preload and the rear to high-preload.
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Old 06-21-10, 01:14 PM   #13
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Check Cable Housing at Lever, Too

It's a DiaCompe aero lever with the old, specialized ferrule.


>> Sometimes the point where the cable housing mates within the aero lever can become a point of compression, where the housing is "drawn inward" through its stop in the lever slightly. This chews up the outer plastic covering, and prevents the cable from relaxing quickly, as the housing eases back out from its stop when you release.

Just check to make certain that the housing tip isn't chewed up. That'd be the sign of a problem there.
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Old 06-21-10, 01:46 PM   #14
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Quote:
Originally Posted by DannoXYZ View Post
Make sure you separate cable-friction from caliper-friction. Disconnect the cable from the rear-brake and pull on the inner-wire and alternate between pulling it versus squeezing the brake-lever (flossing the inner-cable back and forth). Due to the length of the cable-run, housing-compression and friction, you can never get the rear-brake as crisp as the front.

A lot of calipers have adjustable spring-preload. I typically set the front-brake to low-preload and the rear to high-preload.
The above suggestion (essentially isolation of the problem) is the first place to start. That way you don't get a lot of guessing as to the cause or cure. To explain further and generalize:

Friction in a brake system can be anywere from calipers to the lever, so you need to see where the problem lies. As above disconnect the cable from the clamping bolt on the caliper. then work the calipers by hand - should snap back crisply with no hesitation. Then pull the rear lever all the way to the bar. Move it back and forth (it will now have no resistance from the cable, and should move easily). Finally, hold the end of the cable and work the lever back and forth while you pull back on the cable. When done you will know where the resistance is and can focus on that part of the problem. Do cable in sections if not continuous housing.

Last edited by cny-bikeman; 06-21-10 at 04:05 PM.
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Old 06-21-10, 03:54 PM   #15
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This "viscous shock absorber" thing is the funniest thing I've heard in a long time!!! While it's true that I will use the lightest grease on hand for break cables, the notion that it could measurably slow it down is delightfully bogus.

The old Diacompe aero levers (and I still have a pair on an old Cannondale) are notoriously friction-ey in part because of weak springs and less than ideal routing. I used to dread these on bikes cause it required so much work to get them snappy. Use the best quality lined cable you can and be very picky about the routing of the housing, esp out of the lever. Avoid wrapping over the housing on as much of the bar as you can. Also pay attention to the routing at the rear of the bike.
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