Front sprocket question

[Premature Accelerato]

I have recently purchased a new sprocket and chain set for my bike and am wondering why the new front sprocket is different from the one currently on the bike. The one on the bike appears to have a rubber or hard plastic boss or packer on each side while the new one is (for want of a better term) naked. It goes on ok and will probalby do what it is supposed to but what is the purpose of the boss on the other sprocket. I am not sure if the old sprocket is the original or not.

[nzspokes]

If it fits the spline then it is fine.

[Big Dog]

Some front sprockets have an offset to put the chain perfectly in line. To reduce wear.
If it fits on and there is not a difference in how far out the teeth are from the case or the alignment of the chain you'll be fine.

If you ordered a model specific one I is unlikely to be wrong. If you did not buy the previous one it could be wrong.

[Drew]

Dunno why some sprockets have the rubber bits on the side, but it's common on original equipment. Can't remember ever seeing it on an after market sprocket though.

It'll be sweet so long as the thickness is the same, and offset.

[nzspokes]

Dunno why some sprockets have the rubber bits on the side, but it's common on original equipment. Can't remember ever seeing it on an after market sprocket though.

It'll be sweet so long as the thickness is the same, and offset.

They have it for shock loading like a cush drive.

[willytheekid]

Yeah, its just a cush like spokes said...think its more for sound dampening tho

[Katman]

They have it for shock loading like a cush drive.

It's nothing to do with 'shock loading'.

The rubber gives the side plates of the chain a pair of soft shoulders to run on thereby (as Willy said) reducing noise.

[bogan]

Interesting stuff. I've not seen one before so spent 2 mins on google learning more, indeed they are for quietening and not shock loading like a cush, apparently the chain link style has to be narrower in center rather than flat too, which makes sense and I haven't seen the flatter style ones in fucking ages anyway.