Any reason why you didnt go with their kit all of the way around your car?
The credit card wants to come out!!
Do you think the upper tubular a arms are worth the extra money?
The profile of tires like 245/45 or 275/40 is a percentage of the width. So a wider tire like the 275 must have a lower percentage of the width to get the same height as a narrower tire.
What you should look for is the outer diameter, it is usually specified in the datasheet from the tire manufacturers.
My tires are 275/40X17 and 245/45X17 and they both have 25.7 inches of outer diameter.