As above, bearings, standards, numbering and nomenclature has got my head spinning.

Can anyone please put up a link to a lower bearing that will fit to a 2017 Dartmoor Primal 27.5 and/or a Dartmoor Blink headset.

The size seems to be 52 x 38.1 x 5.7 45/45.

But can I find one using my own t’interweb skills?

Can I bollocks….

I’ve got a 2017 Primal Plus frame and it is IS42/IS52 – although the bike is no longer a bike – more bits scattered everywhere.

I put a generic brand X one in mine from CRC iirc.

This is all I can find from a quick google.
https://www.wiggle.co.uk/cane-creek-40-series-headset?lang=en&curr=GBP&dest=1&sku=103211695

And the geometry sheet is
https://dartmoor-bikes.com/sites/default/files/documents/2017_Dartmoor_MTB_frames_geometry.pdf

edit. Your measurements above seem odd. The IS52 bit means Internal bearing and 52mm diameter. Most of these are for tapered steerer forks which have 38.1mm steerer tube width at the bottom. Some of the IS52 bearings are 40mm internal diameter but I suspect they are for the same fork – just with a little lip on the crown race that sits slightly inside the bearing taking up the difference between 38.1 and 40mm.

Then the 5.5 is the bearing height, which again I think is part of the IS52 standard, but you could measure the depth of the frame cup to be 100%

Lastly, 45 is the angle of the chamfer. Again a standard for the frame IS52 and the lower bearing usually comes with a crown race so the angle on this will be to match the bearing it comes with so is largely irrelevant.

Damn, too late to edit. Your measurements are not odd and it’s 5.7 not 5.5, I couldn’t get to it in time to edit that bit out.

My measurements are, to put it politely, bollocks – sorry!

I’ve repacked the old bearing with decent grease and it seems fine.

I found an old FSA lower bearing whilst I was at it and although it sits maybe a millimetre higher on the crown race when pushed on by hand I reckon it could easily do service as a spare.

Thanks for the info. It is the 5.7mm that makes it a bit odd, I think. I will resume my search later…