I recently purchased a 2001 S500 which came with the stock 16-inch wheels. Am preparing to put the 18-inch AMG double spoke wheels on. Specs on the S500 state that recommended tire pressure is 29 in the front and 32 in the rear. Does that only apply if you're running the sixteen inch wheels? Are different pressures called for when the eighteens are installed?

Use the MB sticker on your car for all sizes. I have 20" rims and tires on my S500 and find that 30 PSI front and 32 PSI rear works best all around for me.

The sticker is different for each configuration. Your best bet is to find (or ask someone with) an S55 and check out their sticker. I forgot what mine said, but it wasn't any of the figures quoted.

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.

I run 34/36 psi on the 18" AMG rims with Goodyear F1 tires. This recommendation was from the Tirerack representative. Works great for me, I only drive when the weather is warm.

I run 30 in the front and 34 in the rear in my 06 s500 with 18 inch amg rims on michilin pilot sport xl ultrahigh performance tires.