Sunday, February 27, 2011

Shimano Ultegra Shifter Jamming After Broken Cable

Last year the cable broke inside my Shimano Ultegra 10-speed rear shifter. The cable was just 6 months old with less than 3000 miles. I rode home and found that I could not remove the nipple end fragment of cable. I could shift back about 5 gears by creating some torque on the shifter drum with the sharp end of a small screwdriver, but I could not get all the way to the "small cog" end of the shifting range. I finally removed the unit from the handlebars in preparation for taking it apart. I made one more try, and found that the loose cable end had apparently moved, no longer jamming the mechanism, and I could rotate the drum back to home position and remove the nipple and cable fragment. The nipple was still in its socket.

Well it just happened again, this time after 13 months and about 3000 miles. This time the unit was totally jammed. I removed it from the handlebars and rapped it a bunch while holding it in various positions. It finally started to "shift" but this time the cable fragment was no longer seated in its socket and was badly jammed way underneath. It took about an hour of shaking, shifting and probing with tweezers and wires to get it out.

Unlike older shifters which had a drilled hole where the cable sits in its socket, this 10-speed shifter has a notch. This makes it much easier for the broken end to fall out and jam the mechanism. Thanks, Shimano.

Both cables were genuine Shimano. Perhaps some other brand will last longer.

(In the process, I tried to remove the combined main shift lever and outer shell to get at the loose end. I got as far as a small Phillips head screw underneath the lever with a locking plate. Even with the locking plate disabled I was not able to loosen the screw.)

Lessons learned:
  • Replace the rear shift cable every 2000 miles and the front every 4000.
  • If the cable breaks, try to resist repeated clicking of the shift lever, which just rotates the loose end to the bottom where it will fall out.
  • If the cable breaks, try to get the loose piece (cable end and nipple) out of the shift lever immediately. Riding the bike is likely to jar it loose.
  • If the shifter is jammed after a broken cable, try inverting the bike and then shaking it or tapping the shifter with something like a screwdriver handle.