Accelerometer readings on a moving object
A few things to consider. 

First. An accelerometer isn't that great here. Low output frequency is one issue. Noise is another. A pot or an optical encoder would be better. 

Secondly. Even if output frequency isn't an issue. You will need some sophisticated math to reconstruct the instantaneous tilt, as the measurements are essentially a sine function, but with an acceleration away from the center of the rotation.  Getting to the max tilt is easier mathematically. 

Just for starters.