Shimano bar end shifters wear out?
I have some Shimano bar end shifters - 8 speed - that I've been using for probably upwards of 10,000 miles. Interestingly, they worked fine as far as I can remember when I was using them on a drop bar, however I just converted my bike to a trekking bar and I'm using the barcons with Paul Components Thumbies and I seem to have lost some of my indexing detentes. I get a positive click on 1st and 2nd gear (smallest cogs), yet there is nothing for 3rd, 4th, and 5th gear and the shift lever needs to be finessed to get it to shift and stay in a gear. Oddly enough 6th, 7th, and 8th all still have a positive click. If I set the shifter on friction mode it works without issue. Nothing has changed about cable routing either. I'm using the exact same length of shifter housing coming off the new locations of the barcon/thumbies as I was using when they were installed in the ends of a drop bar. Cables are all routed properly going under the bottom bracket as well. I can operate the shifter in friction mode, but I'm wondering if I hooked something up wrong or if something could've gotten broken inside the barcon. I know these are pretty simplistic units and should have a pretty long lifespan - longer than 10,000 plus miles I'd imagine. I unfastened the shifter from the thumbie mount to see if I'd had anything set up wrong, but it looks like there's only one way to correctly put the whole thing together anyway. The only thing that has changed is I was using a SRAM chain before but I put a new KMC chain on instead since the SRAM chain had taken a beating this last winter. I checked the SRAM chain with a Park Tool chain checker and it still is well within limits so I don't think there's an issue with one chain having stretched and thus worn the cogset. The cogset only has about 2500+ miles on it so I'm sure it's not excessively worn either. Any thoughts as to what's going on here?