Mountain Bike Reviews Forum banner
1 - 5 of 5 Posts

· Registered
Joined
·
2 Posts
Discussion Starter · #1 · (Edited)
Hi all, I am after a bit of advice.

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. I took 2 links off the chain length as per the instructions but this didn't help.

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
 

· Registered
Joined
·
96 Posts
That's definitely not normal. Shifting should be quick and snappy in all gears. It's acting like a bent D hanger although you said that checks out normal.
Other possibility is that the rear derailleur is improperly installed with the affixing tab on the derailleur mounting pivot not fully seated against the flat part of the hanger. It's easy for this to happen and, if so, you'll never get the B screw setting exactly right.
To check this, place the derailleur in a middle of the rear cog position. Then loosen partially the mounting bolt. If there's an improper gap you'll hear a snap as the slack is corrected. Retighten the mounting bolt, take slack out of the cable and then readjust the B screw setting in the largest cog.
If that's not the problem, I would swap out the hanger, derailleur and shifter with new ones, at least as a test. If it's still bad, then i think you have a frame alignment problem. Good luck!
 

· Registered
Joined
·
2 Posts
Discussion Starter · #4 ·
Thanks for the replies.

I have tried a new hanger and checked it with an alignment tool. I have also tried literally every position on the barrel adjuster and the deraileur is seated correctly withe the b screw tab right up against the hanger.
 
1 - 5 of 5 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top