Got a Cotic Simple fitted with a WI freewheel and a rear chainline of about 57mm. I have a new double SLX crankset to fit to the front which I am going to fit with 1 x 32 chainring. Trouble is, the stated chainline for this crank is 48.8 so I will need to fit a further 8mm of BB spacers to push the chainline out to get a straight chainline.
Choices I have are fitting the additional spacers but there are already 2 x 2.5 spacers drive side without adding any more so I might have to consider a deep cupped BB such as a Saint to ensure I get enough threads into the BB. Or I can try and fit the (On One 32t) chainring to the outside of the SLX spider to push the chainline out further. But it looks as though the spider tabs are shaped on the outside and not flat.
It was so much easier with a triple cos I just used the outer fixings for the big ring.
The WI Freehub is on a DMR revolver rear hub so there is no adjustment possible at the back
All advice gratefully received.

TBH when setting up a SS drivetrain you’re better off just seeing if it works.

I had a bike a few years ago that would lose the chain if the chainline was even slightly out. However, my Krampus seems to be fine with anything. On paper the current set up is miles out, but it runs smooth as anything.

so I will need to fit a further 8mm of BB spacers to push the chainline out to get a straight chainline.

Don’t do this. The crank axle isn’t long enough.

It was so much easier with a triple cos I just used the outer fixings for the big ring.

Sounds like the chain line is designed around this?

Sell the cranks and buy some triple ones off ebay?

I think the easy answer will be reverting to a triple chainset as before. Looking at taking the old XT triple off my geared bike and putting that on the SS with the new chainring on the outer tabs.
I can then put the new SLX double onto the geared bike (which had been converted to a double a while ago) – sort of puts that right.
I’m pretty sure the 9 speed setup on the geared bike will work on a 10 speed crankset.