My 38's rub a little too, only when turned hard left, or right. They've doen this for about a year, even since I got them, and I haven't had any problems. I am however cautios of it, and try to avoid truning that sharp, when possible. The only effect I have, is that the paint on the Radius arm whrere it rubs, got rubbed off.
Ok than dont turn that far . I never looked to see if there are steering stop but if there is thay could be adjusted but with that size tire you may just have to live with it