2016 C4 - Heavy steering and vibration?

[georgealex]

I would expect the steering to be lighter with overinflated tyres.
At a guess I imagine that there will be a defect in the power steering itself. Is it electric or hydraulic?

Yes it hasn't really changed the steering weight.

It's both electro hydraulic, no obvious issues there clearly is still some assistance, no whining, fluid fine etc

[georgealex]

30 psi / 2.1 bar seems a bit low, is this the pressure from the sticker on a door pillar ? As myglaren says, I would expect too high a pressure to give lighter steering but a harder ride. Our last C4 had 205/55 16V tyres according to a check on Kwik Fit against its reg.

Yes same tyres on this one, correcting the pressures hasn't caused steering to change but I imagine it could be the cause of the vibration I was getting on the motorway.

I wonder if I'm just over thinking it and the steering is "normal" for this car, there's a few for sale near me I might try and test drive one for comparison.