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Rear gear cable change

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Rear gear cable change

Old 04-26-22, 12:45 PM
  #1  
tgoode
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Rear gear cable change

My rear gear cable broke at the paddle shifter and I've pulled out the old broken end and replaced it with new outers and inner cable (Shimano optislick). I screwed the barrel adjuster all the way in on the back derailleur and then backed it off a whole turn and then attached and tightened down the new cable.

I am able to shift from the smallest cog / highest gear only a couple gears now and the shifter will not shift down to the largest cogs (9 cogs). I've backed out the barrel adjuster all the way trying it in half turn increments and it doesn't resolve the issue. Before the cable broke I was not having any issues with shifting through any of the 9 gears on the rear.

Road bike is a Cannondale Synapse with Tiagra 4500 groupset. 3 x 9 = 27 speed.

Any thoughts as to what to check next?
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Old 04-26-22, 12:48 PM
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dsbrantjr
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Set the shifter for the smallest rear cog (most cable payed out) and make certain that the chain is also on the smallest cog, before securing the cable.
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Old 04-26-22, 12:55 PM
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tgoode
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The shifter and chain was set to the smallest cog when I secured the cable. I thought that it might have been tension related so I've released and secured the cable a few times now adjusting the slack in the inner cable. I still get the same issue. I can only make a few gear shifts and it will not shift into the lowest gears.
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Old 04-26-22, 01:21 PM
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cxwrench
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Sounds like you need to pull the cable out, shift the shifter to the high gear position and then run the cable through it and to the derailleur. Or some other mistake...I can't believe what I see when people bring bikes in to the shop that they've 'fixed'.
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Old 04-26-22, 01:38 PM
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smd4
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Is the shifter bottomed out?
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Old 04-26-22, 02:18 PM
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SoSmellyAir
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Originally Posted by tgoode View Post
Any thoughts as to what to check next?
Follow the steps shown in this video step by step ...


... without assuming that anything you have done before was done correctly.
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Old 04-26-22, 03:52 PM
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Before even attaching the cable, confirm a few things:

1) Is the derailleur hanger straight? (If landed on, the R derailleur (and/or hanger) can bend. It should be straight, first and foremost. But if it is bent, even a little bit, this changes the effective adjustment of limit screws. The "H" limit screw will appear to be too far in (clockwise), and the "L" limit screw will appear to be too far out (counterclockwise). The derailleur's range of adjustment has simply been bent inward toward the wheel. Also confirm the hanger is tight. They can loosen over time, especially if not installed properly at the factory.

2) Are the limit screw adjustments correct? This is completely separate from cable adjustment. The cable tension has no bearing on the derailleur shifting into the large and small cogs and not past them. This is the function of the limit screws. Once derailleur and hanger position and installation are confirmed, then limit screws are set. Once this is done, you've confirmed that the derailleur shifts through the entire range without overshooting the large and small cogs.
Note: If the R derailleur is old or damaged, it may be the problem due to excessive play in the parallelogram or jockey cage. Also confirm the jockey pulley screws are tight (usually with a 3mm allen).

3) Now that the above are done/confirmed can you install the new cable & housing. Now adjustment should ONLY be an issue of cable tension. I've found over the years that pulling on the cable with your hand as you tighten the cable clamp screw on the derailleur is often the proper initial tension the cable needs for good shifting. However, if installing new cable, housing & ferrules, then the system needs to be "stretched." "Cable stretch" is really a misnomer, as it's really cable housing & ferrules seating in place during initial installation. After "stretching" the cables, I then re-attach the cable at the derailleur. This usually achieves proper tension. Then confirm by shifting "up" one cog at a time until you can go one up, back down, then two up, two down, and so on until you're through all the cogs.

You did good starting with the barrel adjuster one turn out from all the way in. This is good practice.

A common mistake is mixing cable tension function and limit screw adjustment. And the biggest faux pas? Adjusting limit screws AFTER doing steps 1-2 above in a failed attempt to address cable tension problems. Don't ever do this!!!! Incorrectly adjusted limit screws can kill!
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