Lower offset won't have any effect on bump steer, you are probably thinking of steering kickback. Bump steer is the toe change of a suspension as it moves through its bump/droop travel and is not affected by wheels. You are dead right about lower offsets generally increasing tramlining though, but 10mm from stock isn't cause for too much concern in my opinion. My car with +15 9.5s (+45 stock) and -5 camber could be a bit of a handful but adding a bit of caster has tamed it significantly.
Bookmarks