Bumpy ride. Is it the casing or the inner tube?
OP said:  


  Well I still had a warranty on my wheels so I've changed them. They
  stopped being true I think. When rolled at high speed the wheel
  (without tubbing and tire) was very unstable.


Hooray for warranties!  Remember, always keep your receipts, and don't procrastinate or the warranty window may close on you.