GY-521 gyroscope/accelerometer breakout board

So, I have one of these working well, and saving data to a SD card. One thing Im having trouble with though is changing the default sensitivity of the accelerometers.

I see from here that 0x1C is the register for accel settings, but this code:

Wire.begin();
Wire.beginTransmission(MPU);
Wire.write(0x1C);
Wire.write(3);
Wire.endTransmission(true);

does not seem to have any affect.

Is there something that I am missing?