Are the 550s or m packages that come with 19 inche wheels the same rolling radius overall as the regular 18 inch sport package and the regular 17 inch stock wheels-I believe the 17s have larger profile tires and 18s have a bit smaller and 19s are even smaller but all radius overall is the same.

So the wheel well is essentially filled the same with all cars but there is just more rim in the 19s and less tire and more of the tire sidewall in the 17 compared to rim-is this correct

I believe it is
17s-225-50-17
18s-245-40-18
19-265-30-10

So is each drop in 10 points on the middle number equivlenet to an inch? of tire

 

There are many sites on the internet that can show you the exact math.
Everything depends upon your particular tire size. You can plug in the exact tire size on these sites to get your radius.

As I recall, when I was looking at the standard tire sizes that most of us use, the 18" were a little bigger than the 17", but suprisingly, the 19" with low profile tires was nearly the same size as the 17".

It all has to do with the profile of the tires that you get.

Another interesting thought. The large radius tires do play tricks with the speedometer. If you lease the car, does the larger radius of the tires trick the odometer into believing that you are traveling less miles?

I hope that this information helps, and good luck.

 

Hmm that is an idea-find a way to put like 22s on your car and get twice as good "gas milage" or so the odo will think