Chain popping off

It's possible that the chain is rubbing on the front derailleur, but I don't think that is why the chain is "popping off the gear". Is the chain coming off the front chain ring? If so, then the front derailleur is probably not adjusted correctly (either the limit screws or the cage is not properly aligned).

If the chain is coming off the rear cog, then it's the rear derailleur that's not adjusted properly (either the "h" limit screw or the cable tension).

Either way, the solutions are to either visit your local bike store for a quick fix or to visit the Park Tool website. They have a great site filled with instructions on how to make the adjustments yourself.

John Swanson
www.bikephysics.com

Warjcowski said:

Whenever I'm in the smallest rear gear I hear a clicking sound and then my chain will pop off the gear. It looks like my chain might be rubbing the front derailment. Are there any guidelines for spacing on the front derailment?
Thanks

Its the front cog that keeps popping off. Ill check that site. thanks for your help

I'd check chain line too. Sounds like the rear cluster is in board of the granny ring.
Is it a different rear wheel/chainset than the one the bike was sold with?
Zanda

It is a different chainset that the one the bike made with. I did a few of the adjustments the site mentioned and the chain no longer pops off, but there is a loud clicking sound when I shift into that gear. I think the front derailer is a a little high, but i havent had the time to check it yet. What do you mean by the rear cluster is in board with the granny ring and is there a site that could explain what to look for to find out and gives a fix? Thank you for your help.

ZandaBailey said:

I'd check chain line too. Sounds like the rear cluster is in board of the granny ring.
Is it a different rear wheel/chainset than the one the bike was sold with?
Zanda

"What do you mean by the rear cluster is in board with the granny ring and is there a site that could explain what to look for to find out and gives a fix? Thank you for your help."

'In board of' means 'left of' as you sit on the bike and 'out board' means right. The granny ring is the smallest cog at the front. Cluster is the group of sprockets on the freewheel at the rear.

Here's a site that talks about chainline:
sheldonbrown.comchainline.htmlOpen ↗

The chain should be a straight line for most of the gears, like in this photo (bikeloves.comchainline.jpgOpen ↗). I think the the trick is to get the chainset and cluster in line with each other.
If the rear cluster of sprockets is slightly inboard of the chainset, the chain, guided by the rear derailleur, can be dragged off the smallest chainring. This would happen when you go over a bump or when you pedal really hard.

To check chainline you measure from the centre of the axle to the centre of the middle cog, front and rear should give the same distance.

Swapping the original chainset for another can alter the chainline, which is why it's worth checking.

Hope this helps. It could be other things, as others have said. Would need to see it. A friendly bike should give you the time to figure out what the cause is.

ZandaBailey said:

"What do you mean by the rear cluster is in board with the granny ring and is there a site that could explain what to look for to find out and gives a fix? Thank you for your help."

'In board of' means 'left of' as you sit on the bike and 'out board' means right. The granny ring is the smallest cog at the front. Cluster is the group of sprockets on the freewheel at the rear.

Here's a site that talks about chainline:
sheldonbrown.comchainline.htmlOpen ↗

The chain should be a straight line for most of the gears, like in this photo (bikeloves.comchainline.jpgOpen ↗). I think the the trick is to get the chainset and cluster in line with each other.
If the rear cluster of sprockets is slightly inboard of the chainset, the chain, guided by the rear derailleur, can be dragged off the smallest chainring. This would happen when you go over a bump or when you pedal really hard.

To check chainline you measure from the centre of the axle to the centre of the middle cog, front and rear should give the same distance.

Swapping the original chainset for another can alter the chainline, which is why it's worth checking.

Hope this helps. It could be other things, as others have said. Would need to see it. A friendly bike should give you the time to figure out what the cause is.

The chain can not be straight for most of the gears. It can only be straight, if ever, for one combination of big ring and cog, and one combination of small ring and cog. Chainline is not a distance measurement, it is a parallel measurement. The cogs and ring gears should be parallel to a steel rule placed on the center of the cassette and centered between the two ring gears. If it's not, the bottom bracket needs to be moved left or right.