My 67 Morgan +4 vibrated violently between 53 and 60 mph.  I had the wheels
balanced with 4 oz of lead, the steering gear box tightened and the
suspension examined.  Still no luck!
On a visit to the Morgan factory, Peter Morgan, introduced me to the front
end man at the factory.  He said most of these problems are solved by
simply replacing the tires.  I bought four Dunlop 165 x15 tires and all the
vibration disappeared. (The tires were not worn and looked great so I never
suspected the tires.)  The Dunlops cost $50. each, and were well worth it.
Hope this helps.
Lloyd Shields, Minnesota Morgan Club
67 +4 Morgan, 60 Bugeye   
  
 
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