ldonnay
01_1983_Biopace
In 1983, Shimano released a first crankset with "non-round" chainrings: the biopace models were meant to improve pedaling efficiency by reducing the "dead zone" in the pedaling cycle. Chainring were not oval, but a mix of ellipse and oval. The Biopace crankset had 3 ovoid chainrings. Shimano applied this on all cranksets until 1993. More information here: Biopace - Wikipedia
Today, oval chainrings can still be found:
*
roducts MTB, XC and Marathon Bikes (rotorbike.com)
*
absoluteBLACK | World’s best OVAL premium Chainrings
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SRAM proposed an oval option for his Eagle groupset in 2017: Review: SRAM Eagle X-Sync 2 Oval Chainrings | bike-components (bike-components.de)
But these options remain a niche. More interesting is to observe that single chainrings are now mainstream in MTB since the introduction of XX1 group by SRAM in 2012, confirmed in 2016 with the 1x12 Eagle.
Today, all manufacturers offer a 1x (1 by) solution for MTB. For a neo retro build, first choice is a X01 Boost/DUB Crankset, in 175mm with a 34T chainring.
01_1983_Biopace
In 1983, Shimano released a first crankset with "non-round" chainrings: the biopace models were meant to improve pedaling efficiency by reducing the "dead zone" in the pedaling cycle. Chainring were not oval, but a mix of ellipse and oval. The Biopace crankset had 3 ovoid chainrings. Shimano applied this on all cranksets until 1993. More information here: Biopace - Wikipedia
Today, oval chainrings can still be found:
*
roducts MTB, XC and Marathon Bikes (rotorbike.com)
*
absoluteBLACK | World’s best OVAL premium Chainrings
*
SRAM proposed an oval option for his Eagle groupset in 2017: Review: SRAM Eagle X-Sync 2 Oval Chainrings | bike-components (bike-components.de)
But these options remain a niche. More interesting is to observe that single chainrings are now mainstream in MTB since the introduction of XX1 group by SRAM in 2012, confirmed in 2016 with the 1x12 Eagle.
Today, all manufacturers offer a 1x (1 by) solution for MTB. For a neo retro build, first choice is a X01 Boost/DUB Crankset, in 175mm with a 34T chainring.