[Reaperactual]

Yes, one 2.5mm spacer on the driveside for 73mm shell widths.

68mm shells require all three, one spacer on each side plus the 2.5mm driveside spacer.

 

[Reaperactual]

Thanks for confirming! What I find strange is that the recommendation seems to focus solely on shell width but doesn't mention rear spacing, say 135 mm vs 148 mm.

73 mm shell and 148 mm spacing should logically need to push the chainring 6.5 mm (148-135=13. 13÷2=6.5) further out to center the chainring on the cassette.

Or is this extra needed offset handled by the crankset?

No worries.👍

Yeah, as mentioned it's just for bb installation to make sure the overall width including the shell, spacers and bb cups matches the spindle width.

When all is fitted correctly as recomended the actual chainline quoted for your crankset will be accurate at 52mm.

I've got the M7000-11-1 non Boost (49mm chainline) crankset which is set by the mounting of the chainring on the spider arms.

 

[Reaperactual]

Mine also has another set of 64bcd bolt holes too. It's definately a 49mm (technically 48.8) chainline based on the 96bcd chainring mounting point. I also measured it as accurately as I could with a digital vernier gauge.

I'm running this on a 148 Boost bike because it slightly favours the low end of my 11 speed cassette more.

52mm is basically the 'safe' standard chainline for Boost bikes so there's no worries about chains hitting wide tyre shoulder knobbles or chainring teeth clearance on slightly wider chainstays for Boost frames.


Newer style direct mount Shimano cranksets also share the common 52mm Boost chainline which they state is still suitable for both Boost and non Boost bikes.

Again the shell width is irrelevant because a 68mm shell has one 2.5mm spacer on each side to effectively make it 73mm plus one 2.5mm driveside spacer anyway.

You could put the driveside spacer on the non driveside instead to alter chainline but that obviously offsets the whole crankset rather than just the chainring.

 

[Reaperactual]

Arnea, yes, it's a lie that's why my next crankset will probably be an M7100 with an aftermarket 6mm offset chainring if I can't source old style non Boost crankset for sale in future.