Crankset tightening

Any advise on this is welcome: the SRAM manual says to tighten the crankset to 50Nm but then the crankset doesn’t spin freely, as if the bearings are compressed too much.

I’ve replaced the BB and now I’m on the way back installing the crankset and ran into this problem. There is absolutely no play in the crankset after tightening.
BB is 68mm threaded GXP, the crankset is a Gates S300 self extracting crank that looks exactly like the SRAM S300 crank, the bike is a Cube Editor. The curious thing is the SRAM BB manual wants me to install two spacers as the frame is 68mm wide, but the bike came without these with the same SRAM BB.

From page 21.
road-cranksets-and-bottom-brackets-user-manual-eeu.pdf (sram.com)

Adjust the number of spacers until the wave washer is only about 1/2 compressed at the required torque.

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With GXP there must not be any spacers used. The non-drive side bearing is the fixed bearing dealing with the axial loads in both directions whereas the drive side bearing should not see any axial loads.
The torque makes sure the crankarm slides onto the conical interface of the axle all the way until it touches the bearing’s inner ring and squeezes it against the shoulder on the spindle.

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What bottom bracket? SRAM’s GXP bottom brackets don’t need spacers between crank and cups (at least for threaded cups, BB30 may be different). But other brands have a different design and come with a wavy washer to keep the bearings from walking out of the cups over time.

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I guess that is the way to go, as the bike came without any spacers. The old bearing cups measure the same as the new ones. The spacers are 3mm each, misaligning the crank with the rear sprocket. These belts are sensitive so that is a nono.

@MarkPgh & @David_Walker: The bottom bracket is threaded, no wavy washer supplied and no wavy washer according to the manual. Pressfit uses a one.

Ingredients for fixing a bike: some parts, tools, a manual, common sense and invaluable help from around the globe.

Thanks guys.

Page 14 Threaded GXP BB:
mtb-cranksets-and-bottom-brackets-eeu.pdf (sram.com)

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I had the same problem with a set of Vision Trimax cranks (FSA rebadge). Solution was simple, remove them and replace with a square taper crankset

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If the crankset is GXP standard, then you need a GXP bottom bracket. As your frame has a threaded bb housing you’ll have to either use spacers - 2 mm is probably the maximum - between the bb shell and the non-drive side bb cup to align the front belt wheel with the rear one. Or you’ll have to use spacers between the drive side crankarm’s tabs and the belt wheel.
If you use spacers between the non-drive side cup and the bb shell you have to make sure that the drive side crankarm doesn’t touch the drive side bb cup’s bearing as this will cause the bb to bind.

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