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Derailleur install with a used cable

6K views 31 replies 16 participants last post by  jimPacNW 
#1 ·
So I've just installed my second derailleur and it went really well, really smooth. Easy Peasy as they say.

IF you don't count the 15 minutes I spent trying to feed the splayed out cable back through the little holes on the derailleur. I did better this time and only had ONE piece of wire not make it so I snipped it off as it started to unravel.

There's GOTTA be an easy way to snip off the cap of the cable so you can remove the old derailleur and still make it easy to get the cable back into the derailleur holes.

I tried some tape but there's not enough for the tape to stick to. So I just twisted and twisted and twisted and twisted until it seemed it was as tight as it's gonna get the tried to stuff it through. Failed twice so did more twisting and tried again.

Without this step I'm golden. Is there a secret? Care to share?

BtW... this is a SRAM X7.

Thanks!
 
#7 ·
Fair thought except as soon as I snipped the cap off it blew up. I may try to glue it BEFORE I snip it. Maybe some JB Weld or something? I'll give it a shot...

I'll check that out later tonight. Thanks!

Why would you replace the derailleur without replacing the cable and housing? To me that's like doing half the job.
First: 'Cause I don't know how to change a cable or housing... yet... :(

Second: Because even though the trails I/we ride are very rough a banged up derailleur or hanger doesn't necessarily mean the cable or housing was even touched. I've destroyed a derailleur on it's first ride down a particularly treacherous trail we love. I've had several others with under 10 rides on them. This is my fourth derailleur this year.

Yeah, I know. I need to learn how to ride. Tell me something I don't know. I don't enjoy easy, XC trails. If it ain't chunky it ain't fun. Unfortunately, that means I buy a lot of derailleurs...

After I check out that video above does anyone have one for replacing the cable & housing? I'll need to learn to do that someday.

Thanks.
 
#6 ·
IF you don't count the 15 minutes I spent trying to feed the splayed out cable back through the little holes on the derailleur. I did better this time and only had ONE piece of wire not make it so I snipped it off as it started to unravel.!
You should go ahead and replace the cable. Eventually that loose strand is going to start binding and cause shifting issues.
 
#9 ·
The key to not fraying a cable when cutting it is to use a really sharp cable cutter (not side cutter), if it does come unravelled a bit it's real easy to twist it right again as long as the cut was clean.

I agree with customfab though that if you are replacing a derailleur it is sensible to replace the cable and housing, it can make a world of difference.
 
#10 ·
The key to not fraying a cable when cutting it is to use a really sharp cable cutter (not side cutter), if it does come unravelled a bit it's real easy to twist it right again as long as the cut was clean.
Yeah, I figured that was part of the problem 'cause all I have are a pair of wire snips which, by design, flatten the cable out...
 
#14 ·
I've had a Park CN10 for at least 15 years. Just used it this week converting one if my bikes to 1X10. Still sharp, easy and fast to use, cuts cable and housing. In the $35 range most online retailers. IMO a must tool for any home mechanic who does any derailleur or cable brake work.
 
#20 ·
Ah...... the dreaded re-using cable and getting it back through the derailleur puzzle. Customfab knows what he is talking about so take his advice in regards to replacing cable/housing as often as possible. However! One of the tune-up services my shop offers involves removing the derailleurs and cleaning them in a parts washer. It's hard to call the customer and tell them they need new cables when our service menu clearly does not mention the above tune-up requiring them. Obviously if they need new cables that's a different story, but if their cable is good it sucks when you fray it into a million strands when trying to re-assemble. I deal with this daily and this method works for me 8 out of ten times. Do not cut the cable at all. Pull off the end cap with a pair of pliers. The end of that cable has been sitting smashed together under that end cap for who knows how long and is usually fused together pretty damn well. It goes right back through without any problems. Usually.
 
#22 ·
Do not cut the cable at all. Pull off the end cap with a pair of pliers. The end of that cable has been sitting smashed together under that end cap for who knows how long and is usually fused together pretty damn well. It goes right back through without any problems. Usually.
DUH! Why didn't I think of that? It's just crimped on... :facepalm:
 
#21 ·
There is no good reason to reuse a cable. If money is so tight that an extra $2 is the issue, get the next cheaper derailleur (a new cable on a deore derailleur will shift better than an old cable on XTR). If you don't know how to do it, this is a good time to learn. The cable may look fine, but it isn't.
 
#24 ·
NO! Brake housing is strong in the sense that you can put a lot of pressure and it isn't going to break and leave you without brakes.

But brake housing is more flexible than shifter housing when it comes to compression. Any time you use a cable, be it for your shifters, bike brakes, or emergency brakes on your car, there is pressure on the housing -- not stretching like the inner part, but the opposite -- compressing force.

This compressing force makes the brake housing shorter. It is, after all, a coil of wire or basically a spring. This compression affects the positioning of the device it is controlling. This would cause shifting to not work well -- the derailleur must be positioned very precisely.

For brakes, the compression of the cable housing doesn't matter so much -- the brakes still work fine because all you are doing is squeezing something. The exact position of everything doesn't matter. But who knows, cable compression may be the reason that hydraulic disk brakes feel so solid by comparison.

(I have never tried brake housing on shifters. This info is just based on what I have read. If anyone has the time to try it, or has done it accidentally :) , I would be interested in hearing the results .)
 
#25 ·
Hmmm... well, I'll take your word for it but I don't really get it.

The actual cable is metal wire and can't stretch too terribly much. If it did it would be worthless for shifting since precise alignment is necessary. But I don't see how the housing can do anything like stretch or compress. It simply surrounds the cable. If the cable moves freely within the housing then the housing obviously can't be affected by any stretch of the cable and the positioning of the derailleur, assuming it is functioning correctly, demonstrates that the cable is moving freely. Both ends of the housing are anchored independently of the cable itself so the cable can't be affecting the housing.

Yeah, I don't get it but people smarter than me have figured it out so I guess I'll go with it...
 
#28 ·
But I don't see how the housing can do anything like stretch or compress. It simply surrounds the cable.
Ok, sorry I didn't explain it better. If the cable run was perfectly straight, then what you say would be true. But in real-life, where the cable makes turns, the center part of the cable places force on the walls of the housing, causing a compressing force on the housing.

Imagine if you replaced all of your cable housing with soft rubber tubing. What would happen when you go to stop or shift? Nothing! The rubber tubing would just compress, and the brake or derailleur would not move.

Of course the steel does not compress to a point of total collapse like our rubber tube does, but it compresses a little -- helical brake cable moreso than linear shifter cable.
 
#30 ·
I have successfully soldered cable ends and have reused without any problems. Occasionally my flux doesn't work well and the solder will not soak into the strands. Will try the super glue option next time. I have often used old rear derailleur cables for front derailleurs with good results.

urmb
 
#32 ·
I use an ancient Suntour cable cutter, many are available new that are probably better. I have a Performance house brand cable housing cutter.
Like stated above, once the cable end gets frayed too close to the rear derailleur cable clamp it gets replaced and saved for use with a front derailleur.
You can buy a little jar of clamp on cable ends for just a couple of bucks on ebay, a lifetime supply for most people. I also bought the 25' roll of that XTR/DA quality Shimano cable housing on ebay, probably about a year ago. I think it will last me a long-long time. It's usually the rear piece of cable housing that goes bad long before any housing in the front, so it's nice to be able to replace the rear housing whenever I feel like my shifting is not quite as good as it should be.
 
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