While trying to fit my front arms, I tried to get the 5.3 deg castor angle but found that I needed to mount the top arm off the front chassis member. So I went back to the drawings and checked everything and it all seems to be OK I then drew it in CAD and found that if the parts were made and mounted as per the book drawings the castor angle is only about 2.53 deg. What is wrong?

The book ! Do a search and you should find loads of post about castor. Some have repositioned the upper mounts and some have remade the wishbones to give the correct castor.

Out with old faithful again
Rescued attachment Wisbone Modification.JPG