Shimano's Biopace crankset, launched in 1983, uses oval chainrings to smooth pedalling and reduce dead spots. Unlike other oval designs, it reduces the effective diameter in the power position to promote smoothness. Several versions were produced (Biopace II, HP, SG) before the range was discontinued in 1993. Although it was criticised for its efficiency at high cadences, it remains popular with touring cyclists. Today, it is sought after by vintage bike enthusiasts.