Well, have just put four (ouch) new tyres on the GS.
Went to a pukka place to have it done who were well recommended. Very happy with the service. Got the feeling they definitely knew what they were about vis a vis wheels and tyres, having phoned then 25 times first to check what I could have.
Drove it home and the car was as hard as nails - every pebble made the windows rattle. Checked the pressures at home. Manual says 32 psi. I have in the past run them at 35 psi just to try, and prefer the 32. However, this tyre place had racked them up to 42 psi. Crikey!
Put them back to 32 and all is superb now, quiet as anything, grips like a werewolf, smooth again.
Why would they put them so high though? (I KNOW I could ask them, I wondered if there were opinions here!). They're a "performance tyre" centre; would you run a performance tyre higher than normal perhaps?