First of all I recommend you do some measurements (because it's a lot cheaper than anything else!) then work out if you need to change anything to sort your bump steer.
There seems to be some confusion about bump steer from what I've read above. Here's a neat little article on what it is, how to measure it, how to change the amount you're getting and what is good vs bad.
http://www.fastgrandad.co.uk/documen...terham%207.pdf
It's for a lotus 7 type vehicle, but then, would you expect anything else from me?
Treeve