Front chainring/gearing

[Jimbo747]

Hi all,

Recently bought a new Cube Reaction Hybrid Performance 500. This is my first electric bike. I’ve done 120 miles on it in the three weeks I’ve had it and find it fantastic. I’ve not owned a bike since I was a kid (30 years ago), And perhaps stupidly had the bike delivered for me to build myself.

My question is this: in the highest gear (8/9) the front chain regularly jumps off and gets rammed between the chainring and the frame. What am I doing wrong?

jimbo.

 

[Nealh]

Probably a set up issue.
In the short time of use have you knocked the derailleur at all or lent it against anything.
Check each chain link manually and make sure one isn't stiff or twisted, raise the rear wheel up and slowly cycle the chain over the chain ring.
Is the chain too long ?
If no joy fit a chain keeper.

 

[Jimbo747]

Probably a set up issue.
In the short time of use have you knocked the derailleur at all or lent it against anything.
Check each chain link manually and make sure one isn't stiff or twisted, raise the rear wheel up and slowly cycle the chain over the chain ring.
Is the chain too long ?
If no joy fit a chain keeper.

thanks. My sense is that it is just a set up issue - can’t figure out what I’ve done wrong is all.

 

[Darren Hayward]

Does the derailleur have a clutch (a grey T shaped lever on the front of the derailleur)? It stiffens the derailleur arm and stops the chain jumping of all the time.


Darren

 

[Kwozzymodo]

You might need to adjust the High Limit screw, to limit the outboard derailleur movement

 

[MichaelM]

Do you mean the lowest gears (biggest sprockets on the back wheel) or do you mean the chain is jumping off the smallest sprocket, rather than jumping off the chainring?

If you mean it's jumping off the small sprocket and ending up against the chain stay, then I agree it's probably an adjustment problem. If you look at the derailleur from the rear, you'll see two screws close together, one above the other. The top one is probably the one you want. I think you have the same derailleur as I do, Shimano RD-M3100 (Alivio 9 speed). This video shows the adjustment 5 minutes in.
https://www.youtube.com/watch?v=bxDvnwnj7f4

EDIT: Just re-read your post and I see you say "front chain". If it is jumping off the chainring, it could still be derailleur adjustment. There are only three screws, plus the cable tension, to adjust. It's all in the video linked above.

Is the chain reasonably clean, and lubricated?

I should say I'm not a real bike mechanic, but I have just successfully adjusted what I believe is an identical mechanism.

 

[R Benny Waered]

I have one of these and had to set the gears all up from scratch despite it being built by the bike shop - it was quite a sh** first ride! There are some good videos on you tube on how to do this - its slow and fiddly first time so take your time and see how all the controls interact. Make sure the 'maintenance mode' pin that locks out the derailleur in its longest lowest mode isn't pushed in.

 

[jimriley]

I had issues with chain jumping of my bbs01 front ring, though all was set up ok. Fitted a chain keeper/guide, not happened since.