They are 18x9.5 and 17x8 and the stock lug nuts do tighten all the way down on the wheel but I am concerned with where the lug contacts the wheel. The stock nuts have a round contact area rather than a flat cone /\. thanks
It is not advisable to use the stock lug nuts for aftermarket wheels that are designed for the cone type lugs. They will not seat properly. And overtime they will become loose or uneven torque value. Which can cause warping of the rotor or even worse, come off. I seen this happen to a few people when I used to work for speed shop.