Why should anyone align, balance or centre the wheels of a tractor? Quite simple, because also these vehicles are getting faster all the time. They don't however, reach the speed-ranges where balancing makes itself noticed.
Due to the fact that tractors are nearly always only sprung through the tyres, when they reach a certain speed, the tyres go off-centre and start to hop. Just a marginal note: The rim- and the tyre manufacturers are in dispute about who's responsible for this disaster. The above shown measuring method clears up the dispute and shows which is at fault quite clearly.
It clarifies whether the greater off-centre-runout is coming from the tyre or from the rim. Indeed, it can do even more, the solution to smaller errors is presented in the form of matches. The rim and the tyre are turned in opposite directions to each other, so that the greatest offset in the rim corresponds to the smallest in the tyre and vice versa.
Tractor-rims are of course not mass-production articles. The smaller the series, the greater is the chance that errors can occur. One can't even always be certain, that the rim corresponds perfectly to it's own bowl. The tolerance is given with an accuracy of tenths of a millimetre or less, sometimes however, considerably more than one millimetre is determined.
Because the measuring itself is carried out without contact, it's very simple. One sets up the laser-device and plugs in the connections. After that, it's best if one only touches the jacked up wheel itself, to rotate it. Everything else is done by the electronics. Have a look at the lap-top display in picture 3, you'll recognise that such a large wheel is comparatively exactly measured and that there can be a considerable amount of inaccuracy in both the tyre and also even in the rim. Apart from a precise measuring result, the programme also offers at least a partial solution to the problem. 09/14