Hard to find staggered 18" Y99 tire set.
 

Hola amigos! I'm trying to find the staggered set for 18" tires that fit 08 STS v6 AWD, playing by the manual in order to workaround constant tire rotations you stagger the tire set up> Front: 235/50ZR18 99Y Rear:255/45/ZR18 99Y
This set is hard to find, the rear is available but the front is only available in 'R' but not 'ZR' or it's a 101Y not a 99Y. Has this staggered combination been updated and which combo is the best? Because they're not going to all be ZR or they're not going to be all 99Y.
Mind you that the 3.6l engine is quite heavy and all front components (brakes, coil springs and tires) wear faster than the rear ones.