When I first had a car in the 1970's the trend was to have your wheels balanced "on the car" and that if you subsequently removed the wheel you were supposed to refit in the same position relative to the hub. I always thought that the physics was a bit dubious as the moment of inertia of a wheel is more determined by the mass at the periphery than the hub. Does anyone know why we don't do that anymore, or was it just a 1970's marketing concept?

Garage I worked in the 60s and 70s had a Churchill on car wheel balancer it was meant to balance out slight imperfections in the hub and was great for spinning up wheels when looking for noisy wheel bearings.

I think the reason is that wheel balancers have got more sophisticated. Doing it the on-car way, you could only fit a weight in one point on the wheel - usually on the outside of the rim and it was near impossible to use that method on the rear wheels due to the axle casing. With the wheel balancers nowdays you can balance the inner and outer sides, the middle or any combination that suits the style of wheel using clip on or stick on weights. There is even a 'hidden weight' programme on our one that allows you to put on the correct weight using stick on weights so that the weights are hidden behind the wheel spokes irrespective of where the actual heavy spot on the wheel is.

Most cars were rear wheel drive during 60's-70's, and accurate balance was achieved balancing front wheels on car.
My RS Mexico and RS 2000 I always balanced the rear wheels on a front hub, also did this for customers cars which had drumming/resonance problems usually caused be remoulds on the rear. All FL2's (3) Gone
2011 Mercedes C180 CGI Gone
FL2 GS Auto SD with heated leather, factory tints, alloy spare and a few other bits.