Mercedes-Benz 2009 SL-Class Operator's Manual page 347

Mixed size tires
Front axle
Model SL 550
Rims (light alloy)
8.5 J x 18 H2
Wheel offset 1.38 in (35 mm)
21 255/40 R18 95W
Summer tires
or
255/40 R18 95Y MOEx-
tended
21 Radial-ply tires
22 Must be used in conjunction with Tire Pressure Monitoring System (U.S. vehicles) or Advanced Tire Pressure Monitoring System (Canada vehicles) only.
SL 600
8.5 J x 18 H2
1.38 in (35 mm)
255/40 R18 95Y
or
255/40 R18 95Y MOEx-
22
tended
SL 550 (Sport Package)
SL 600 (Sport Package)
SL 63 AMG
SL 63 AMG (Performance Package)
SL 65 AMG
8.5 J x 19 H2
1.18 in (30 mm)
255/35 ZR19 96Y XL (Extra Load) MO1
22
Technical data
Rims and tires
Z
345