Hi,
I just put new tires on my S90 this week and ever since I put them on if I take a turn somewhat sharp it feels like the rear end is trying to break lose and is sliding around. They inflated the tires to almost 38psi when I cheked them so I let some air out since i ran them at about 29 before. This didnt seem to help. I was wondering if they could have broken something on the rear suspension when they put it on the lift or just need to have the rear end realigned. They are a higher performance tire than what was on there before. Can someone please help me?

Thanks

How many new tires did you buy?

Where did you mount them: Front or Rear?

I replaced all 4

I thought you had replaced 2 tires only and put them on front (which unfortunately many people do).

I believe that the problem you describe here is an oversteering situation.

Try to inflate the tire accordingly to the Volvo's recommendations and respect any pressure differential front/rear (if any).

Lower aspect ratio provide a better grip on dry but are more susceptible to hydroplane on wet conditions (hence the V-shape of the grooves for channelling out the water). I can't belive that your tire dealer would have made such a stupid mistake but if you have uni directional pattern, make sure the tire are rolling in the proper direction!