In the case of the M3W, the front swingarm pivot point is close enough to the center of the BB that it will probably not matter if you're on the ground or freely suspended off the ground. The only issue with being on the ground is that if the car is under load in one direction or the other, that portion of the belt, top/bottom, can be slack or tight depending on the load. So probably to help it would be best to check this with the car cold and the rear tire off the ground. Also as Harley suggests, the belt tension should be checked in different parts of the belt as to take into consideration of any possible high spots on the pulleys etc. The tension is usually then set at the tightest spot.
I'm sure that it will be figured out soon and everyone can then do the same setup.
I hope I've not confused the issue.
I have always assumed that the centre line of the bevel box drive belt pulley is exactly on the swinging arm pivot point. Designing it to be close enough would be a pointless exercise when there seems to be no reason for it not to be exact (engineering tolerances aside), allowing belt tension to remain constant throughout suspension travel range.
Richard
2018 Roadster 3.7 1966 Land Rover S2a 88 2024 Royal Enfield Guerrilla 450 1945 Guzzi Airone
