Find out, wrap a piece of string around it, and measure the circumferance, let me know if you dont know how to convert the circumferance to diameter.

What trim level is your EM1??
Weather the EM1 subframe is a concern is somthing im completly unsure of, maby somone else can chime in. All i know is that the ek hatches that didnt come stock with a swaybar need aditional bracing.