I have a high end mountain bike frame (out of warranty) where the aluminum shock pivot that goes through a carbon tube has become loose.
It's still in place but can wiggle approx 1mm.
I can see a small gaps where I could get epoxy into, but I also have 4mm of tube external to the carbon I could build up

This is the sole rider weight/compression bearing pivot, so I'd need a high strength epoxy..perma 515 maybe?
Many thanks in advance

ET515 is ideal for bonding bottom brackets back in to place.  As long as the movement isn't too bad you will be fine.  Spend plenty of time sanding the carbon to a rough finish and the same on the aluminium. Both surfaces need a good key to help the glue to mechanically adhere.

If the gap is quite big, laminate in some fresh carbon and build the thickness back up.  Obviously the rough laying up of carbon would need to be cut back and sanded round again until the bottom bracket fits tightly in, at which point you can then bond it into place as above.

Warren Penalver
Easy Composites / Carbon Mods - Technical Support Assistant