Are my tires causing my car to swerve and follow the cracks?

Usually caused by unusually wide tyres/wheels. This is called in the UK 'tramlining' and is nothing to worry about though can be disconcerting. Owing to the increased width of Z3 spec. tyres over standard tyres there is more of a tendency to follow abrupt changes in the road surface. Keep those hands at 'Ten to Two' on the steering wheel.

Uncle Lodger.