Self Centering - lack of

[Enoch]

Wotcha peeps. Just driven my car round the roundabout at the back of my house. I was somewhat surprised to find that it has no self centering action whatsoever I have eccentric mushrooms with the offset hole towards the front, the suspension brackets are all in the correct place, everything seems to be nice and free but the steering wheel stays wherever I put it. What other things can effect the self centering? I thought it was mainly down to the caster angle set by the offset mushroom. I notice that my rack is quite low and so the track arms are at a fairly steep upwards angle - would this be anything to do with it.
All thoughts accepted gratefully.
Enoch