I bought a Huster Super Z last summer. When I'm driving it down my paved drive way it seems like one the back tires is not balanced very well. When your drivining it down the drive, it feels strange... It's like a real uneven ride. Hard to describe. I really do not notice it when cutting my grass because the lot is so rough anyways. Any tips or ideas why it would do this. I've ensured the tire pressure is good and equal in each tire.