I have a new JDztrak. when I run it full tilt on stones on pavement, the front wheels wobble back and forth BADDLY. the wheel on the right usually is first. I checked the air pressure in both wheels and they are the same. I didn't check the rear wheels yet. I have had my scag z for 4yrs and have run with 1 flat tire on the front so I'm a little stumped.