Tires: tires, michelin x one, inflation pressure

Question
Hello i have a 92 caddy deville and it has michelin x one tires on it, i am looking to replace since i see dryrot under the tread, my first question is what tire will give me the smoothest ride possible?   My elderly parents complain of a rough ride, and that should not be for a caddy, struts are new, also would upgrading to a different size help any, the original is 205 70r15  thanks so much.  

Answer
Mark,

You vehicle came equiped with P205/70R15 inflated to 30 psi.

Check your placard to see if this is correct as the next step is 100% dependent on that info being correct.  The placard is usually located on the doorpost or in the glove box.

You should have enough room to go up a size to P215/70R15.  Because you went up in size, you can go down in inflation pressure and still have the same load carrying capacity.  I recommend 26 psi, the lowest pressure I consider safe for P metric tires (ones that start with "P")

I'd also recommend you get your own pressure gauge, because some folks think you should use what is on the sidewall of the tire.  That's the maximum, not a recommendation.

Hope this helps.