you want to space the rear out much more than you have it.the width of the car really will depend on the tires you are running.if you are running parma tires,they are a narrow offset and make the rear extremely narrow and you will need to use more shims.the jaco,crc,and TRC tires all have a wider offset which will require less shimming.i run asphalt and i usually run my rear at 168mm and the front at 165mm.for carpet you may want to be closer to the 172mm limit in the rear and maybe 2-3mm more narrow in the front.try it out and see what works better for you.