Just picked up a new (to me) mountain bike. It was working fine riding around the neighborhood yesterday – no crazy riding – but I hopped on today and the shifting is all messed up and the chain came off.
I’m hoping it’s an easy fix but it’s biting my noob diagnostic skills. Can anyone here give me some guidance?
by Gmichael317
4 Comments
B tension. Google how to adjust the b screw on your derailleur and you will be fine. 10 second fix.
The little B-tension notch that is built into the derailleur isn’t sat correctly. So basically, your derailleur has not been installed correctly and thus the B-screw does nothing to increase tension (hence why at ~15s in the video, where you rotate the RD, there’s a screw that’s not touching anything.)
You need to uninstall your RD, and remount it. You can see the notch/tooth which should be able to rotate. https://i.imgur.com/MGCeete.png it needs to rotate clockwise to sit against the notch on your hanger.
Maybe your B-screw broke. [https://www.parktool.com/en-int/blog/repair-help/rear-derailleur-adjustment#article-section-5](https://www.parktool.com/en-int/blog/repair-help/rear-derailleur-adjustment#article-section-5)
Looks like the derailleur hanger is on back to front.