Chorus rear shifter question

[jchasse]

I just re-built an old frame with some new Chorus UT stuff, and I’m having a problem with the rear shifter.

When the chain is shifted all the way to the small cog in the rear, the problem comes when trying to make the shift back up to the second cog. When you first press the shifter paddle, it feels as if it hits a mechanical stop, it never reaches the detent (no matter how hard you press) and won’t make the shift. Usually, if I back off and try again, it will shift flawlessly on the second try and it shifts well through the rest of the cogset. So the problem is ONLY there when shifting from the smallest cog to the next larger one.

All parts are new 2008 Chorus and are “QS” parts.

I really don’t think I have the indexing off one click, because I’ve built enough bikes to avoid that mistake (I think), I have tried to diagnose that particular condition, and everything’s kosher at the other end of the cassette. Cable tension, stop screws etc all appear to be fine. It really seems like a shifter problem…

Do I have a messed up shifter? Could it be something funky with my shifter cable housing?? Or am I just missing something obvious here?

[bigbill]

If the thumb tab hasn't spring returned all the way up from the upshift, it will mechanically block the shift lever from moving. New stuff might require a break-in period before it moves freely. You might try a drop of triflow or similiar on the pivot of the thumb tab.

Another thing to check is if the shifter hood or handlebar tape are interfering with the movement of the thumb tab. I did that once.

[pdxmech13]

My guess would be the thumb lever as well.
Try lubricating the pivot on the thumb lever.

[jchasse]

Thanks guys! Looks like you were both right. I lubed the crap out of the thumb lever pivot, and voila! Seems to be workin like a charm!!

Cheers! :beer: