I used a plumbers wrench with several layers of inner tube. Had to grip so hard that I raised a burr on the collar. Fast forward 6 months when the past went back under warranty due to a huge amount of play. It came back with a note saying there were signs of tampering, fixed as a good will gesture and warranty void. With only 3 months warranty left I thought this was a bit petty. I called Customer Services and was told that unscrewing the collar was not allowed, all you can do is clean round the collar and spray some silicone. I was also advised to prise the seal away from the stanchion with the thin bit of a cable tie and shove some grease in. My advice is to undo it as above and save up for a One Up, the Company has an enlightened approach to user servicing.