More info would be good to diagnose your situation. But I'm guessing you're talking about the crank arm wobbling on the spindle. Most likely, the spindle is worn down. So now when you put new cranks arms on it, the cranks do not fit snug enough. I'm assuming we're talking about a bmx bb. If not, you're prob. in the wrong thread. Anyway, I'd try getting a new spindle. I had this same problem recently. Good luck!