Wrong chainring?

[Chief Broom]

Told yer.

Nope its falling off again....

 

[Sharky]

Mark the chain again and determine if its falling off at the same links.

 

[Chief Broom]

Mark the chain again and determine if its falling off at the same links.

It seems random now- it may spin 5 times ok then falls off, this is on a brand new chain

 

[Alex321]

It seems random now- it may spin 5 times ok then falls off, this is on a brand new chain

Is it the right width chain?

If you have an 8 speed cassette/freewheel, then you need a chain designed for 7-9 speed - and a chainwheel designed for that as well, though a chainwheel designed for higher numbers should be Ok, it will just mean there is sideways play in the chain on the chainwheel.

 

[Chief Broom]

Is it the right width chain?

If you have an 8 speed cassette/freewheel, then you need a chain designed for 7-9 speed - and a chainwheel designed for that as well, though a chainwheel designed for higher numbers should be Ok, it will just mean there is sideways play in the chain on the chainwheel.

Its the right chain exactly the same as the one removed. Im convinced i have the wrong chainring which allows the chain to shift about which would explain why its ok one minute and not the next

 

[Alex321]

Its the right chain exactly the same as the one removed. Im convinced i have the wrong chainring which allows the chain to shift about which would explain why its ok one minute and not the next

It is very possible you have a 10 or 11 speed chainring, which would give some sideways play, because the teeth on the chainring will be narrower (as would a 10 or 11 speed chain).

 

[ColinJ]

Is the chain the right length? (Not sagging just before it falls off.)

 

[Chief Broom]

It is very possible you have a 10 or 11 speed chainring, which would give some sideways play, because the teeth on the chainring will be narrower (as would a 10 or 11 speed chain).

That sounds about right, the teeth on the original look nothing like the new one.

 

[Dogtrousers]

OK Here's a theory. Probably nonsense. How old is the cassette?

If the cassette is worn and the chain new then perhaps the chain might start "skating" over the teeth of the sprocket. In the biggest sprocket this might be enough to lift the chain high enough and it's offset enough that it can disengage from the chainring.

 

[Chief Broom]

Is the chain the right length? (Not sagging just before it falls off.)

Its absolutely the right length- i measured against the old one.

 

[Chief Broom]

OK Here's a theory. Probably nonsense. How old is the cassette?

If the cassette is worn and the chain new then perhaps the chain might start "skating" over the teeth of the sprocket. In the biggest sprocket this might be enough to lift the chain high enough and it's offset enough that it can disengage from the chainring.

New cassette about a month old

 

[Dogtrousers]

New cassette about a month old

Bah. Worth a try.

Hope you get it sorted.

 

[ColinJ]

It is very possible you have a 10 or 11 speed chainring, which would give some sideways play, because the teeth on the chainring will be narrower (as would a 10 or 11 speed chain).

I have used 10 speed chainrings with 8, 9, and 10-speed chains on my singlespeed bike without any problems.

The problem I did have was when the chain tensioner wasn't taking the slack up properly when I hit bumps in the road - the tensioner bounced, the chain slapped about, and fell off.

Its absolutely the right length- i measured against the old one.

I thought the old chain was falling off as well!

 

[richardfm]

Its absolutely the right length- i measured against the old one.

Did you count the links or measure the length?
Was the old chain worn?
Was the old chain the right length?
Have you checked the chain line?

 

[Chief Broom]

I have used 10 speed chainrings with 8, 9, and 10-speed chains on my singlespeed bike without any problems.

The problem I did have was when the chain tensioner wasn't taking the slack up properly when I hit bumps in the road - the tensioner bounced, the chain slapped about, and fell off.


I thought the old chain was falling off as well!

The old chain was fine with the original chainring apart from occasional 'skipping' when a lot of pressure was applied- hence the new chainring. Ive a feeling were going round the houses when its the new chainring which is wrong!