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I'm restoring a 29 AA, last year I removed the front axle, dismantled it completely, sandblasted, primer and paint, reinstalled it, I did not check caster angle. The wishbone is not bent or damaged in anyway. I have read that there is no front or back to the axle. The king pins are new, and the spring perch shaft and the hole in axle are not wore out. I rebuilt the radius ball with all metal parts. Now I have checked the castor angle with an angle degree finder and a carpenters square on the floor and I have zero degree castor. I measured this close to each king pin and in center of axle, all the same.
I really need your help
thanks nick c

How's your front spring and shackle? In guessing your front spring has sagged...

The shackles are new, if the spring was sagging I think it would have some positive castor? Is it true that there is no front or back to a model aa axle?
thanks nick c

28/29 front axle is same as cars - spindles and spring perches are AA specific tho - spring perches should be cast AA-XXXXX number in them.

think of the front axle as this:
Take a compass (thing that draws perfect circles - pencil in one hand and sharp stationary point in the other), imagine the stationary point is the wishbone ball - it doesn't move only rotates. The front axle is like the pencil and moves in an arc. The wishbone and axle are locked together so as the axle moves down you get negative castor and if its flat against the frame its neutral with a bit of positive castor. AS you can imagine your front spring must keep the axle a set distance away from the frame to maintain that 3* negative castor - if its sagged it becomes more positive

FYI most springs especially 28/29 are broken sagged or incorrect replacements - they are 12 leafs just like the standard A's and the standard A's will fit but will be too weak. The AA 12 leaf are thicker leafs thus can handle the loads more (and extra heavy frame etc) but AA's weren't treated nice over the years and many were overloaded and 85+ years has taken thier toll on them.

Very interesting, now we're getting somewhere. From what I've read, with a positive castor the top of the king pin leans back, with a negative castor the top of the king pin leans forward, is this correct?
thanks nick c

Stakebed, are you sure that its a negative 3* castor that I need, that means the top of king pin would be tilted to the front?
I really need your input, thanks nick c

This you tube video may help get a better reading https://www.youtube.com/watch?v=1NOwQzOWNTU
Is the cab and bed mounted on the chassis and you have the correct size tires on a level floor.

Bob