Hello WindyCity,

The setup you mentioned (275-40-20 and 20x9.5 around) will work and look fantastic your X5. Sure there're plenty who have this setup with the replica 87s. The larger rear tires (315) are not necessary although it will give you a more agressive stance. But trust me 275 is plenty big enough.

So go ahead, you won't have any regrets. GL.

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Dinan S1 pkg / 22" Iforged Swift - Toyo 295F*315R / Eisenmann Race - OEM tips / H & R 15mm front
30mm rear spacers / Euro-spec headlights / CF M Competition steering wheel / Full CF interior /
6000K D2S / HID fogs / AiBrights V3 / Interior Xenon / LED sidemarkers / Matte black grille & hood vents