Vibrations through the floor

[Zayd]

I need the help of the wise ones...

When I reach speeds over 65mph I can feel vibrations running through the floor of the car.  As a result I've had the front wheels balanced and the car was only serviced by a reputable garage a month ago.  They would have picked up any knackered traction control arms and bushes so I could possibly rule this out as well.  I've never experienced that the wheel alignment would cause this problem and the car appears to be straight as an arrow with its steering and no pull to any side. 

The only thing I can come up with and a long shot it is.  My front tyres are Michelin Pilot Primacy's and the tread have a straight line pattern.  The rears are Michelin Pilot Sport's and have the diagnal lined patterns.  Can the conflicting tread patterns cause this vibration. 

[Zayd]

Bump!

[Mantamad]

Not sure if this is of any help but I get a very slight vibration if I press down on the gear stick - I have put it down to the cables vibrating (its a cable operated change) I wonder if one of your cables needs a slight re-routing. Otherwise I would check the wheel bearings, suspension and axle bushes or engine mounts.

[dsl55]

My brother is the tyre expert & he's not around to ask at the moment but am fairly sure you shouldn't mix directional & symmetrical tyres

Might not be why you're getting the vibes but you never know