Chainring bumps and holes

[barracuda]

   

After all these years I had never observed by commuter's chainrings and the interesting shapes they have. Do these holes and "bumps" help with the chain flow or what's the purpose?

[G_M]

(07-19-2019, 06:58 AM)barracuda Wrote:  After all these years I had never observed by commuter's chainrings and the interesting shapes they have. Do these holes and "bumps" help with the chain flow or what's the purpose?

Exactly, those are called 'pins and ramps' and they support the upshifting. You can read about it on Sheldon Brown's page.

[barracuda]

(07-19-2019, 07:56 AM)G_M Wrote:  

(07-19-2019, 06:58 AM)barracuda Wrote:  After all these years I had never observed by commuter's chainrings and the interesting shapes they have. Do these holes and "bumps" help with the chain flow or what's the purpose?

Exactly, those are called 'pins and ramps' and they support the upshifting. You can read about it on Sheldon Brown's page.

Much appreciated, thanks!