Ya know, there is lots of good talk/reviews here about CS4's(many recent posts). Last Oct'10, one of the reasons that I didn't choose the CS4's for my daughter car was that in many reviews, "balancing issues" were common. We went with the Hankook Optimo H727's and are very happy thus far(I can't argue with the reviews). *I'm not promoting the H727's because, time/mileage will still be the final judge here. I actually like our Pirelli P4's better in many areas than the H727's.
Later on, I had reread some of the reviews and there had been now, more possitive reviews than negative reviews causing me to beleive that Cooper had addressed these issues.
I do beleive that the Cooper CS4's are a very good tire and there are many happy customers but, their balancing issues could be due to the lack of calibration in the balancing machine and/or tire tech related(not saying that it isn't the CS4's too). Everybody seems to be in a too much of a hurry all the time when performing work on the vehicles of others and the "this is good enough" attitude!
I use to have a SAM's Club membership and was buying tires from them for a short period of time. Each time I went into the service center(early morning) the manager and a tech were calibrating the balancing machine or the manager was training a different tech. This SAM's Club store in particular did a great job of balancing tires. I was buying G/Y tire there and as typicle(in my experience) G/Y tires need rebalancing often so, I frequented this SAM's store often for my tire purchaces and rebalancing.
I have also found one particular Good/Year Service Center that performs the absolute best 4 wheel allignments I have ever gotten in my life. Over the past 25 years, they are the only place that I'll let do my allignments. They calibrate their equipment frequently(balancing machines too)
When their done with the allignment, the vehicle drives straight, steering wheel is straight and they'll even first do an allignment check for FREE and give you the results. Often showing that an allignment isn't needed and there are other issues. I don't just go into that G/Y Center for an allignment unless I susspect something amiss. Sometimes it's the tires pulling to one side or another(radial pull-again, typical of G/Y tires).
I'm just blabbing again but, my point is: When you find a shop that does good work or a product that gives you good quality, stay with it! I just wish that I could find both in one place but, it ain't happenin' so, it causes me to drive all over town.