Hello again Tom,
Thanks a lot for your help so far. I still ponder about two problems though:
1) When you're at an angle, taking a corner - how can you know the exact angular velocity of the corner (to calculate g-forces), as the gyro axis along which you measure is now under an (unknown) angle.
Do gyro's always measure from a fixed plane? If so then the above problem would be solved
2) When you know the actual driving forces from your GPS/speed + angular velocity, how do you know to substract them from the accelero data? You don't know what direction the forces are applied, so you don't know how to substract them from the accelero data in order to have only gravity direction remaining.