Is it possible to use my old xt cranks with Bergtec ring on my new boost frame. Is it as simple as adding 3mm spacers between ring and spider.

Not sure about xt ring offsets but I use non boost settings on all of my boost bikes even with a 3.0 tire on my Solaris max.

How old / what model are your XT cranks?

I think 2015. They are set up 1×11

If the chainring clears the chainstay and the chain doesn’t rub on the tyre, you’re good without any spacers. I’m also running a non-boost crankset on a boost frame.

I believe there might be more trouble if you’re going to convert to 12-speed.

I’ve got old xt crank on my boost frame with no spacers, what you will find tho is you will have to use a 30t ring ,any bigger will catch the chain stay. My frame is Solaris max and raceface ring

I ran my non boost Saint cranks on my boost frame, was fine with a 34 tooth but couldn’t run a chain device. From what I remember, ideally the chainring wanted to be where the tabs are, position wise.
So if anybody made one, which as far as I’ve seen they don’t. A circle of aluminium with two sets of bolt holes would solve the problem.

Over 11 and 12 speed chainlines compromised anyway imo.

I’d rather have a good chainline in the easier gears where more power goes through the chain than harder gears.

Fit it and see, it’s the only way to check.

I’m currently running normal xtr cranks on a boost frame. No  real issues although it’s only 10 speed as it’s on the winter bike.

I had to but a boost XT crankset to run my 34T oval after destroying my rear swingarm and there being no non-boost versions available in the UK. It wouldn’t even turn fully on the old non-boost XTR crank. So now I’ve a XTR non-boost crankset for sale less than 6 months old as well as a DT Swiss 350 non-boost 12×142 rear hub.

I found the chainring wanted to be inline with the tabs so ended up buying a new SRAM crank which sucked as the SRAM BB, Crank and chainrings are all shit. stupid crappy pointless boost.