Am I right in thinking that if I leave out the driveside 2.5mm spacer on my 73mm hollowtech bottom bracket, the only effect will be to pull the chainring and crank 2.5mm closer to the bike?

And is this actually quite a useful way of centring the chainline if I’m using a 2 x 10 crank but with a single chainring to achieve 1 x 10?

Or is that a load of nonsense and I’m likely to break the bike and myself if I try messing with such dark arts…

Advice gratefully recieved! Thanks.

Put the spacer on the non-drive side if you decide to do this.

Cheers will do. Is that because the bb will screw too far into the cups if not? Or the central tube will be too long? Or another reason.

The tube will be too long – as will the axle.

Cheers.

Can I ask – did you do this and did it work / help? I’m doing the same conversion but was hoping to not need to take the bottom bracket off if possible.

Fit the single ring as is, see what it looks like then decide if you want to move the bb. To keep it right you need the correct number of spacers in place overall, left or right not an issue.

ive done it with success. although the chainline was usable with the original setup, it was quieter in the lower gears when i moved the spacer

Cheers guys.