Sounds as if the bolt circle is different-smaller or larger, thus they won't be centered on the lugs.
That's correct. The studs are smaller than the lug opening on the wheels, but the studs will still all go inside the existing pattern.
Rather than chancing snapping off the studs, you would need something called "eccentric lugs" (aka - eccentric roto-lugs) to accomodate the existing wheels - until the correct lug size and spacing are incorporated into the wheel manufacture.
Eccentric lugs are "off center sleeves" that turn onto the wheel studs. they line up in a "radius" from the center of the hub and fill the space in the wheels' oversized lug openings. I'm not sure if anyone makes them anymore. A company called Appliance Wheels used to, but I'm not sure they still exist / are in business. I used them on several cars back in the 70's and 80's when I couldn't get the wheels I wanted for my car in the exact / correct bolt pattern. They worked well.