[Graham]

This isn't how we measure mag effect, our tester has the cars sitting on all 4 tyres so the mag effect is measured at normal ride height, the mag effect decreases the further the motor is off the track.

Does that setup just measure the motors magnetic strength or is there an air gap between the motor and measuring block? and if there is an air gap how far is it and is it adjustable.

 I think all the questions were answered above, the distance between track and motor is 8mm regardless of tyre height. So in effect the actual magnetic force measured can only be assumed to be much higher for the normal ride heights of the cars. I could adjust the height on the instrument but see no point as it is sensitive enough as it is and all the cars are measured in exactly the same way. So it is the relative difference in test results which matters.