This suggestion hasn't got anything to do with car handling or maximum lock or anything else.
What the OP means is :
- The Ingame 3D model of the (steering) wheels of XRG (for instance) has a lock of 720° (360° in each side).
- His hardware steering wheel has got a maximum lock of 270° (135° in each side).
- When he turns his hardware wheel by (let's say) 90° to the left, the ingame 3D steering wheel models turns by more than 90°. The ratio is, for instance, 90°/135° (2/3), which means, the ingame 3D model will turn 2/3 of 360 to the left, so 240°.
- Then, what he wants is to allow the model to have the same rotation angle as his hardware one (meaning that when he turns 90° to the left, the wheel will turn 90° and have the same maximum lock of 135°), but keeping the same wheels' (the one with tires) lock.
So, as a "résumé", when he turns 135° to the left, the XRG wheels (front ones) will keep their lock of 36°, but the 3D steering wheel will turn 135° instead of 360° (which will change by no means the handling of the car, it will just change how does your cockpit steering wheel model turns).