Originally Posted by Iride01

Shimano rear DR?

The most common recommended chain sizing by Shimano is to not thread the chain through the rear DR and put the chain in the big - big combo. Then add a link or two to get you to the next correct link to split the chain at. There are exceptions though. If it's a 3x front, then many times Shimano will say to do it a different way. Other factors and even different models of Shimano will have different sizing recommendations.

If you have Shimano, then go here and look up your model DR and if it's got a DM use that otherwise what ever other UI, SI or other doc they have for your model DR will usually tell you how they want you to size it.



https://si.shimano.com/#/

I have found similar for SRAM, but they don't seem to make it easy to find documentation. Especially models that aren't in production any more.