They are +2 forward and -2 narrower.
There are more reasons for the narrow rear end. I just stated the most obvious.
It also takes less hp to turn the tires when they are narrow. The wider tires are like a gyro, just takes a little more hp to turn them.
Also as stated above it gets your rear tires out of the ruts and into alot cleaner sand.
On a side note, it is not quite as stable as the wider rear end.
Mine is adjustable and when I race on the dunes I spread the rear end out about 8 inches.
