Boost setup using 6mm offset chainring

[Shredden]

Hey fellas,

My bike runs a boost setup currently, on a 12 speed shimano drivetrain and a 30t front ring with an 10-45 cassette. This is heaps of range for me but I do spend a fair bit of time in the largest and second largest rear cog.

On the other hand, I almost never use the smallest two cogs.

I’ve noticed the chain line is on a fair angle when climbing in the bigger cogs. If I understand correctly, my current boost chainring is offset by 3mm.

Has anyone had experience running a 6mm offset chainring on a boost bike, in order to make the chain line a bit better in the climbing gears (where most of the pedalling is done)?

Thanks

 

[beeb]

I did it with Shimano M8000 non-boost cranks on a boost frame (Ripmo V1). Driveside chainstay clearance was ridiculously tight (to the point it rubbed lightly if there was any grit on the chainring), but shifting was fine. A little easier in the bigger gears if anything, and the chain felt/sounded less distressed. Shimano 12sp may be a hair more finnicky though...

Just as alternative (or combined?) idea, you could try changing to a 28t chainring. That'll drop you a gear or so while climbing, and if you're barely using the smallest gear on the cassette it shouldn't effect that end of things too much.

 

[The Duckmeister]

If anything you probably want to go for a zero-offset (non-boost) ring to straighten the chainline to the inner sprockets.

 

[LPG]

I did see some people recommending the non Boost chainring/Cranks at some point due to chainline. I think it depends on your frame and setup. If you have a threaded bottom bracket you can do some fine adjustments with the BB spacers assuming you have them on your setup. You could move a spacer from the DS to the NDS to make an adjustment.

 

[Mr Crudley]

I did it with Shimano M8000 non-boost cranks on a boost frame (Ripmo V1). Driveside chainstay clearance was ridiculously tight (to the point it rubbed lightly if there was any grit on the chainring), but shifting was fine. A little easier in the bigger gears if anything, and the chain felt/sounded less distressed. Shimano 12sp may be a hair more finnicky though...

I have the same on the 5010 with 11 speed SLX/XT. It works fine and shifting is spot on. The spider on the cranks doesn't give any option to run a boost chaining so I am limited at 30T for now. It still gives me the gearing I'm happy to use so not a bit deal for now but I would need a new crankset if I wanted to run a 32T. I 'might' be able space out the driveside BB cup to sneak in a large chainring but could also make some new and interesting problems that I don't need

Just as alternative (or combined?) idea, you could try changing to a 28t chainring. That'll drop you a gear or so while climbing, and if you're barely using the smallest gear on the cassette it shouldn't effect that end of things too much.

Maybe an oval chainring. The 30T is reputed to feel like a 28T + 32T depending on where you are in the pedal stroke.

 

[creaky]

I think it depends on your frame and setup.

Absolutely. Non-boost chainrings give a better chainline on some frames, where there is enough chainstay clearance for the chainring. Not an option on many frames though.