Front chainrings (eggshaped)
 

Hello,
I have noticed that my front chainrings are , what appears to be, more eggshaped than round. I can clearly notice it when riding and looking down at the chainrings. I am wondering if it is warped?

Cheers,

Shimano offered "Biopace" chainrings several years ago that were indeed "eggshaped" and were said to offer an advantage in pedaling efficiency. They never really caught on and were dropped from the product line but some are still around on older bikes or even NOS. Others have taken up the same idea recently and have found limited success. Check the engraving on your rings and I expect they will say Biopace.

It could also be a SR "Ovaltech" or Sugino "Cycloid" as well as other brands, although those are rarer. Shimano did license the technology to other manufacturers.

They are indeed "biospace", haha too funny. Thanks for the help guys.

TdF 2013
 

I remember seeing last year's TdF winner Froome using a non-round chainring during at least one stage. Camera had it in close-up, and the TV hosts commented on it.

Way way back pre 1991 a friend had a bike with those on it, so I can claim to have ridden them :-)