From past experience, optimum tire pressure varies between tire brands, car models and driving style. Even though there may be numerous 215/45/17 tires used, the sidewall stiffness varies. If you have a less rigid sidewall, like my dealer installed Dunlops (215/40/18), you can consider a bit more pressure to allow less 'give' in hard cornering. But have a stiffer feel in normal driving. Generally you get better straight line traction with a a bit less pressure - giving more road surface contact. But the tradeoff is sloppy cornering. I'm still trying to figure the best pressure to use with my Dunlops on HFP rims. The dealer recommendation is the best place to start. Just my 2 cents.
