When doing my apprenticeship, I was shown one of these discs and told about the accident as well as several other incidents. The disc presented was razor sharp round the edge.

It had become slightly loose and was chaffing on the inside face against the wheel rim, apparently it had worn to a sharp edge in a matter of a few days and unseen.

It was debated as to whether it was a batch of poor sized brackets and softer discs that may have cause the problem which was not common to every bus but they were not identifiable so they erred to caution and removed the lot of all types.

I'm sure a simple solution to eradicate the issue was on the cards but someone saw the cost savings and took advantage of the RoSPA raised issue to force the change.

But for those that do have them in preservation, they do need to be checked just like lights and other parts of the vehicle every time it's taken on the road