chain back pedals

moggie123

Can't figure this ..the gears change fine but when I back peddle the chain falls off ...any advice ?

Type 17

Assuming it's a derailleur setup:

Are you cross chaining?

Is the freewheel/freehub stiff?

Is your chain/entire drivetrain worn out?

Are your derailleur jockey wheels worn?

Miklos

Are you changing gear and then back pedalling?

Wishbone Ash

Why are you back pedalling?

moggie123

The chain and block relatively new .
Jockey wheels are fine.
Free wheel doesn't seem stiff ,but maybe bearings could do with a change/regreecing. It's really baffling. Oh the chain wheel does rotate when freewheeling ( if I'm walking beside bike ). Thanks for suggestions btw.

moggie123

When I say back peddling, it's not much just maybe a rotation when im adjusting bike to lock it up or stuff like that .I wouldn't when normally cycling.
And I don't after changing gear

07Lapierre

Normal enough if the chain is on the big ring and big sprocket.

Cee-Jay-Cee

Happened to me last year and it turned out the chain was 2 links too short. I fitted a new chain and the problem disappeared.

If your chain in new, is there a chance that it was cut/split a link or two too short?

Type 17

Cee-Jay-Cee wrote: »

Happened to me last year and it turned out the chain was 2 links too short. I fitted a new chain and the problem disappeared.

If your chain in new, is there a chance that it was cut/split a link or two too short?

As Cee-Jay-Cee says, chain-length is important - Shimano documentation says that, when the chain is on the biggest chainwheel & smallest sprocket, the bolts for the two jockey wheels should be vertical (or close enough to vertical that adding/removing links would make them less vertical).

smacl

07Lapierre wrote: »

Normal enough if the chain is on the big ring and big sprocket.

Yep, happened to me one or twice inadvertently cross chaining. Staying in the big ring too long, dropping gears coming to the lights for an easier start. Back pedalling half a turn to bring the pedal to vertical for the start and off she pops. While I make a conscious effort not to cross chain, sometimes after a long day the mind wanders off a bit. Keeping the drive train well cleaned and lubed will reduce the chances of this happening.

mossym

what happens if you left the back wheel and backpedal, does the wheel turn backwards?

Type 17

moggie123 wrote: »

...Oh the chain wheel does rotate when freewheeling ( if I'm walking beside bike )...

Sounds like a stiff freewheel/freehub - if it's old, the grease may have dried up somewhat. Dribbling oil into it will help, but some partial disassembly may be required, as the seals designed to keep water out will also keep the oil out

moggie123

I think it's probably the free hub needs attention as the chain is the right length. Thanks for all your suggestions. .