The chain tension shouldn't vary at all with the 'right' biopace rings (1st generation I believe). Sheldon addresses this in length, but the short of it is one generation of biopace works great, others give you tension issues. I believe the OvalTechs are also a no go. I'd have to do some more digging ... Anyways, try it. If you get more than normal variations in tension, it's probably best to go back to round chainrings.