After single speeding my Rockhopper last year, I have now decided that it might work better if it had a few gears 🙂

So last night I put the cassette and rear mech on. Unfortunately when I span the pedals and the chain was on the large ring at the back it would jump off the front chainring.

Currently the chainring is a regular 32t ring with a bash on the outside and the granny removed.

Do I need to put the front mech on to keep the chain in place or is there another way?

unramped chainring might help.

Unfortunately when I span the pedals and the chain was on the large ring at the back it would jump off the front chainring.

spinning the pedals which way?

what happens when you ride and pedal?

Which side did it fall off? frame side? if so get an n-gear jumpstop

Thanks. I take it, it is the groves and stuff that help it to change gear that is also making it jump off?

Rootes1, I falls off onto the frame side – haven’t tried riding it yet. I think it happened when I turned the pedal forwards.

Look for N-Gear jump stop on eBay. It’s just a plate that mounts close to the chainring to stop exactly what you described. About £10 or £12 to buy which is loads cheaper than a proper chain device or even just one of the MRP 1x ones.

try riding it and see what happens – nothing to loose

an unramped chaining helps as these have fuller teeth, if you get one it needs to be one suitable for narrow chains.

a jump stop is only a tenner..

http://www.billys.co.uk/english/group.php?prod=chng-js

on a similar note, I’m getting chainsuck on a 1×9 setup – will running an unramped ring sort it out?