Old 07-28-19, 09:51 PM
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Rear shifter jam after changing flat; trying to diagnose cause

Got a flat today on my relatively new disc wheel road bike. I am still getting used to operating the thru axle so it took me a bit of fiddling to get the axle reinstalled. Well, once I got rolling, I discovered my shifter (Shimano Ultegra r8000) which had been working fine, was jammed.The cable head had slipped out of the recessed cavity inside the shifter, and I want to make sure I know what might have caused that so I don’t do it again. I can’t figure out how I could have affected cable tension enough to dislodge the cable end while I was changing the flat..Two best guesses:

Right after I flatted, I was focused on operating the thru axle and failed to shift to the smallest cog before removing the wheel. The wheel came off easily enough but I shifted down to the small cog with the wheel off to make reinstalling easier.Could shifting without the wheel caused the cable to slip?

While I was struggling to get the thru axle to seat correctly, I pulled the wheel in and out of alignment with the drop outs a few times. In manipulating the position of the wheel, maybe I pushed the derailleur (also R8000) in some way to cause the cable upstream to slacken and cause the head to pop out of alignment? The cable routes internally so the only visible section is the small length that passes through the derailleur pinch bolt.

Editing to add new theory: The internal cable routing emerges from the frsme right at the junction of the chainstay and dropout, with housing passing rigt over the thru axle cap. In struggling with the thru axle, I am guessing I dislodged or otherwise interfered with the housing and cable, causing enough slack to make cable end in shifter pop free.

Alternative theories welcome.

Last edited by DOS; 07-29-19 at 04:45 AM.
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