Are my chain rings knackered?

[Marin Maniac]

If you have a look at the ring you will be able to see two wear points if you think of the ring being a square it will be the left and right hand sides. That is where the power is going into the chain not the top or bottom. So if you turn it 90 degrees you are in some ways giving the chain a new set of teeth to play with.

When you say wear points, are you referring to the chain rotating on the big ring or where you shift up and the chain joins the big ring? I get the jist of what your saying, however it doesn't make that much sense bearing in mind the ring is constantly rotating, so in my fuzzy logic the wear on the ring will be equal around the ring?

 

[spandex]

Ok if you put the RH peddle just at the point where you would start pushing. Going from the crank and around the ring 25% of it is the power point (where you are putting the power down) and then it is the same on the LH peddle. So there are two 25% points you are putting the power down not 100%. The over part of the ring is just carying the chain back round.

As your chain and ring wears down the "25%" is droping to were you just have 3 or 4 teeth pulling the chain (I have see it) that is called shark teeth.

 

[spandex]

Have a look at Sheldon Brown (RIP) maybe he can put it a better way?

 

[Marin Maniac]

Ok if you put the RH peddle just at the point where you would start pushing

This would normally be when the cranks are level (horizontal) yes?

Ok if you put the RH peddle just at the point where you would start pushing. Going from the crank and around the ring 25% of it is the power point (where you are putting the power down) and then it is the same on the LH peddle. So there are two 25% points you are putting the power down not 100%. The over part of the ring is just carying the chain back round.

So essentially you are saying that on each revolution for either side (right or left side) that you are using approx 25% of the ring which equals 50% wear on the ring?

As your chain and ring wears down the "25%" is droping to were you just have 3 or 4 teeth pulling the chain (I have see it) that is called shark teeth.

I think I know what you mean. On the ring there looks like there's about 4x shark fin type teeth which from memory are all in sucession, however I thought some rings this was a feature to aid shifting etc?

Have a look at Sheldon Brown (RIP) maybe he can put it a better way?

Yep thats clear as mud.