Jockey wheel woes
 

After a series of punctures of my jockey wheel and fed up with the pneumatic ones, I bought a complete, 48mm solid wheel and jack last week. The new issue, is the jockey wheel clamp slipping down the jockey wheel post, no matter how tight I try to make the A frame clamp, due to the fresh, shiny galv finish on the post.

The threaded L shaped clamp bolt has a well greased thread, so should be applying a good force. Has anyone had this problem/ found a solution?