Noisy mech on the biggest cog

jeannot18

Just came back from doing the South Downs, and on the second day I started having a problem with the gears. I could not use the biggest cog (with smallest chainring or the middle one [worse on that one]). It was making a terrible noise, first I thought that a spoke came undone and was rattling against something, stopped and check and realised that it was when my gear was setup on the biggest cog. I think it is coming from the front derailleur, but I am not 100% sure. Prior to that as I was going downhill, the chain came off the jockey wheel (??), and I could not pedal anymore. We stopped and put the chain back where it should be. The noise started after that, do you think that I have bent the front derailleur? Thanks for any help, I would like to sort it myself instead of taking it to the bike shop (for cost reason, but also to understand more about fixing my bike)

JC

adesaxo31

If it clamps around the seat tube check that it hasn't twisted round slightly an then check that the rear derailiur isn't touching the rear cassette if it locked up it may have over streched one of the springs. all the best ade

lesz42

B screw adjustment?

jeannot18

lesz42 wrote:

B screw adjustment?

Yes I am going to try that. Looking for a good video if anyone has a link, thanks
JC

supersonic

You don't need a video - adjust the screw so the top jockey wheel clears the big rear cog without rubbing or making a noise. About 6mm is perfect. Screwing in the screw moves the jockey wheel away.

jeannot18

supersonic wrote:

You don't need a video - adjust the screw so the top jockey wheel clears the big rear cog without rubbing or making a noise. About 6mm is perfect. Screwing in the screw moves the jockey wheel away.

Thanks Supersonic, I just washed the bike and had a look on the stand on what was going on, actually when I am on the first cog (biggest one) and small or middle chain ring, the lower pulley wheel arm was touching the spoke of the wheel :shock: . For now I kind of bend back the arm and seems to be ok as it is not touching it anymore. I need to show the bike to someone that knows their stuff and tell me if anything needs replacing or fixing.
JC

Chunkers1980

Sounds like a bent mech/mech cage and/or mech hanger.

supersonic

Yes, sounds more serious.

jeannot18

supersonic wrote:

Yes, sounds more serious.

Yep, took the bike to Decathlon and they said that I need a complete back derailleur. Good news is that it will be replaced under the warranty , the bad news is that I have to wait for them to receive the part .
JC