I have a problem. Do I stick with the pressure the door decal says even though I have changed tire size or do I go with the tire companies specs on the side of the tire?? Anyone with 18"s out there with the answer.

 

215/35/18 maintains the same internal air chamber volume. I would start with 33 psi, and monitor tread wear, or use a pyrometer to judge needed air pressures. Rasing up a pound or two will make your tires feel more nimble, but will cause center rib wear. Its all a trade off.

Alex