Vibration when engine under load.

[Anonymous]

How can tyres become out of round?  I've never heard of this - unless you mean a bulge in the sidewall of the tyre?
Cheers.

I've had this happen on two vehicles; the most recent with Dunlop Sportmaxes on my Contour SE (AKA Mondeo). The car had out of balance symptoms after about 6 months on the tires that balancing would not correct. One tire definitely had a few mm radial runout while spinning on the balance machine and remounting didn't correct it. The tire was replaced under warranty. Problem solved.
The other was many years ago on a VW after a 3000 mile trip cross the US. Car developed the hippity hops and a tire dealer showed me that all four tires were somewhat out of round. He put the wheels on a lathe contraption that had a rotating cutter blade that nicely shaved off the high spots on the tires and solved the problem.
I havn't the foggiest idea what can cause this, but it apparently does happen.
Good luck!
Bruce

[Anonymous]

Well.. that sounds exactlly like what hapened to me in another car of mine.
The problem was a busted engine suport.(the piece that holds the engine to the chassis) Have it checked, cause it seems to me that it's the exact same thing.