[Richard Farrant]

When working in REME workshops years ago, we had problems like this with the Bedford MK 4x4 trucks. We had an electric motor powered roller and a dummy flange for the front wheel so the wheel did not rotate the drive shafts. The wheel was jacked up and roller run up to speed, you soon knew when the critical wheel speed was achieved, by the shaking. There was an optical instrument or strobe, details escape me at present and by using this we could then add weights to the rim at the precise point. It was incredible how much weight was needed sometimes and the thought of one of them coming off the rim on the road was horrifying. I believe the actual reason is tyre circumference not concentric with the wheel rim in a lot of cases, which will upset the balance, also these vehicles stand around a lot and it takes time for them to warm up and the casing to reshape itself. Bar tread type tyres can develop strange wear patterns on the front wheels, none of this helps.

regards, Richard