i use 17s on my car, and for winter i put on some 16's wit winter tires. do i need to align my car everytime i change the wheel sizes? or raise or lower the car a little using coilovers?

 

everytime you raise/lower your car you should go get it aligned, just so you dont have camber problems down the road

 

I do the same thing, though I go from 17s to 15" snowies. No it won't effect the alignment, at least not enough to be of concern. If you raise or lower it a large amount it will change your camber, and should theoretically be re-aligned. Small ride height changes won't make huge differences however. As always keep an eye on tire wear when tinkering with these things. Abnormal tire wear could be a sign of an alignment problem.