dude im running the same size and width rims on my r33 and i have 235/40ZR18 on the fronts and 285/30ZR18 on the rears, and im running tein coilovers and the car sits pretty low. So i dont see any reason you cant run the same width tyres on your 34 maybe even 275/30ZR18 on the rears, And i was running 19s on my old r34 with 245/35ZR19 all around.