[David Olivant]

The 'hand tight' explains why different sizes of spanner are different
lenghts, to compensate for average human force applied.
In many cases wheel nuts coming loose can be attributed to other factors,
namely dirty threads, burrs on the nating surfaces[of nut and wheel and
wheel and axle.
Take the time to clean and inspect all mating surfaces, apply a LITTLE
grease to the stud and tighten with the supplied spanner. I would further
recommend that the nuts be rechecked after a few, say ten, miles.
It works for me.
regards,
David