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Background: I converted a 21-speed bicycle to single-speed by removing the derailleurs and installing a single-speed freewheel and crankset.

The chainline is no longer straight, and I would like to get it closer to straight. At the moment, I'm not ready to re-dish the rear wheel or replace the bottom bracket with a narrower one, and I am exploring more convenient options for adjusting the chainline.

I noticed that, although the chainring that came with drive-side crank is bolted to the outside surface of that crank, the inside surface of the crank also appears to be designed to accommodate a chainring. If I move the chainring from the outside, it reduces front chainline as desired, while still leaving adequate clearance from my frame.

My question is, is this safe? Am I correct in inferring that the single-speed crankset is designed to allow this? (I could not find any mention of this configuration in the instructions that came with the crankset.)

Here is how the crankset looks out of the box:

crankset out of box

Here is the other surface that I think the chainring can be bolted to:

crankset reverse side

Here is how it looks after I move the chainring (on an older but very similar crankset):

crankset with chainring moved

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Looks perfectly safe to me.

In fact, it looks like that crankset's spider arms were designed to also be used as a double crankset for a bike with a front derailleur, with chainrings mounted on both surfaces. Note how the support "fences" inside the bolt holes have the same curvature to clear a chainring that the outside supports do.

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