Glad you posted that.. Crossfire wasn't an issue with new tires.. But the Miata always had that "65 mph" vibration! Never knew what the deal was just accepted it. Put a cross brace on the rear.. made an aluminum brace for the front.. and always wondered if adding the roll bar and tower brace would alleviate it. Seems like the tires-wheels would "sync" up at times and be worse than the normal. Guess I'll try the "dual lock nut" on one wheel trick now!