I would like to install 52-38 Osymetric chainrings instead of my 52-36 Shimano Ultegra R8000 ones.

I've bought the Osymetric chainrings and tried to install them, but I realised I need bolts and nuts to install them (rookie mistake!). That's because the Shimano Ultegra R8000 comes with integrated nuts, therefore I cannot use them.

And now I'm not sure about which bolts and nuts to buy:

The documentation by Shimano about the R8000 chainrings: https://si.shimano.com/pdfs/ev/EV-FC-R8000-4256.pdf

How can I know bolts and nuts will fit on my Osymetric chainrings? Will the fancy ones by Shimano fit on my Osymetric chainrings?

Thanks for your help!

1 Answer 1


Shimano 46 tooth outer chainrings are flat and lack the '3d' profile of the 50 and 52 tooth rings. The 'fancy' bolts you linked to are shaped to cap off the crank spider arms. Those will work with the flat Osymetric rings.

Regular bolts will also work but not look as 'finished'.

  • Thank you @argenti-apparatus, I ordered them (the Shimano Ultegra FC-R8000 Gear Fixing Bolt & Nut Set - M8 x 10.1mm - Y1W898090) and they work. Jul 26, 2020 at 10:54

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