Tire pressure change?
It will also matter what widths you use. S55's were 8.5s front and 9.5s (2001-2002) or 9s (2003-2006) rear. They had different pressure recommendations too, I believe. If your widths are different, your pressures will be a little different as well. My best guess is that 32 front and 34 rear will be closer to start with. My S65 has 19s and the recommendation is 36 all around for three passengers or less and 38 front / 42 rear for four or five. Plus 4 psi if the tires are warm. Plus 4 psi for winter tires. I recall the 18s as a little lower.
The high-performance, low-profile tires you will be running on those rims get to be expensive. You'll be lucky to get 15,000 miles from a pair of rears. The last thing you want to do is run then underinflated.






