12 Speed shifting issues – Page 2 – Bike Forum – Singletrack World Magazine Forum

goopy · 2021-10-11T08:26:20Z

I have a 2021 nukeproof reactor with full SLX drivetrain. I am struggling to get it to shift smoothly and have run out if ideas. The bike shifts from large to small cogs great but when shifting to larger cogs it struggles in a few places (5th to 4th largest, 3rd to 2nd largest and 2nd to 1st largest). The chain will skip a bit until it finds the right tooth on the cog to allow it to shift (tick,tick,tick, tick shift) unless I get lucky and shift at the exact point the right part of the cog comes round. The only thing that seems to help is reducing the chain tension but then I can't shift properly in the smaller cogs. This would suggest to me that the hanger is bent but I have checked it and it is perfectly straight, the derailleur cage appears not to be bent also. I have also played around with every possible position for the b screw and have not been able to find a sweet spot. I have set up the RD from scratch using the Shimano manual and still it won't shift smooth. The chain was 2 links longer than Shimano recommends but shortening it has not helped. I went back to my LBS as it is only about 5 weeks old and done 50 miles and was told that this is normal. This doesn't seem right to me and must be causing unecessary ware on the cassette. Any suggestions or am I expecting too much from a 12 speed RD. Cheers

didnthurt

Posts: 4748

Free Member

'B' screw.....

Posted : 12/10/2021 10:25 pm

endomick

Posts: 0

Free Member

Last time I had a head scratcher indexing niggle I changed my cables and made the outer a touch longer at the rear mech and fixed it, whether it was the new cables or a gentler bend entering the mech I'll never know.

Posted : 12/10/2021 10:52 pm

mashr

Posts: 7135

Full Member

- fixed chain length
- new inner cable
- new outer cable
- correct chain direction
- check cable routing
- new mech hanger
- setup as per manual x 34

Seemingly (just about) ‘ok’ in the stand, total crap out on the trails.

Bought a hanger alignment tool, was a little out so sorted that. Still not a massive improvement. Only things left to change are chain (no indication of issues) or the mech itself….. so I took no prisoners with the latter. After 5-10mins of hauling and checking I now have 12 actual fully functional gears! Definitely still a very sensitive setup, but 1 click up or down now does exactly as it should. That was definitely harder work than it should’ve been!

Posted : 25/10/2021 12:15 am

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[Closed] 12 Speed shifting issues