Knocking is now gone, but I still have a squeaky front end. think its probably the ARB. Looking to upgrade but what size super pro bushes do I need. Also, what other bits will I need?

Assuming you have the bar with the collars, 17mm. And smash the collars off that are underneath the bushes. THAT is usually the cause of the problem, more than the bushes.

Assuming you have the bar with the collars, 17mm. And smash the collars off that are underneath the bushes. THAT is usually the cause of the problem, more than the bushes.

What holds it in place if you smash off the collars?

The squashed bush with the hole 2mm smaller than the diameter of the bar itself. Like most bars.

It'll certainly be a whole lot more secure than the bar which is possibly currently flopping about freely inside these collars.