Tech Friday - Chainline for 12spd on boost frame

[DR ◣◢]

According to the following article the following is indicative of incorrect chainline. 

https://int.oneupcomponents.com/pages/understanding-chainline-for-optimal-1x-conversions-boost-and-non-boost

 

Symptoms of poor 1X chainline

- Premature wear to chains, chainrings and cassettes

- Grinding, rough or noisy pedalling 

- Dropped chains

- Chains that derail when you backpedal while in the largest cassette cog

- Rubbing between chain ring and frame

 

Also: Boost 148 was created to give frame makers more design freedom for tire and front derailleur clearance. From a drivetrain perspective it moves the cassette 3mm away from the frame centerline.  The new ideal chainline for Boost bikes is 51-53mm.

I have the symptom of the chain derailing when you backpedal in the largest cog and grinding, rough, and noisy pedalling in the 10,11,12 cogs at the back but only when the chain is in need of some lube. 

 

Further to this I have a single cog (number 6 I think) that doesn't shift up unless I add a little extra push on the lever. No other gears have issues. 

I measured my chainline to exactly 51mm from center of the bb to the chainring. 
The crank is definitely a boost crank.

No spacer between the bb and bb shell.

My hanger is straight from the looks of it. 

 

I assume the derailing of the chain is normal then and that my shifting issue is related to the Sunrace cassette with SLX derailleur. 

 

And go!