arm out, put the wheel spindle and pivot spindle back in, sit the ends on 4 blocks of equal height,it shouldn't rock. Or put a digital angle finder on the pivot tube, zero it and sit it on the wheel spindle. It'll be a little off, but not a lotYou're spot on, it's steel. I think it needs replacing though, doesn't look straight from right to left. Good excuse to get a whole back end hehe. Is there a solid way to test if the swing arm is alright?