Eccentric Chain ings (Off Center)
 

My SS has some pretty cheap cranks (and chain rings), i have noticed that at certain crank positions the chain is tighter. I take a closer look, the chain ring is not perfectly round.

Today a friend came over with his old road bike, as we take off the chain, i notice that his 52t chain ring is HORRIBLE, its like 3mm off!

And it is the actual chain ring not the mounting.

Is this normal?!

Lots of chainrings are a little oblong (roundness is what often makes the expensive ones expensive). It could also be that you do not have the ring centered properly on the spider. Search around Sheldon's page; he has some instructions on how to do it.

And then, there's biopace. But I've not heard of a 52t biopace chainring.

Biopace, lol thats cool.

52 teeth Biopace rings are very common.

BTW, I have one beater bike set up as a fixed gear and use a Biopace ring. Sheldon writes that it will not substantially effect chain tension. On this particular set up (42x16) there is quite a bit of difference in chain tension as the ring goes around. I do ride it this way, but it really does not seem to be a good idea.

jim