I'm not sure about carrying members of the public in the trailer on public roads,(insurance aspect etc) although it looks like the trailer would meet the health and safety requirements for farm tours. The cracks in the tyre are very common on old tractors and very rarely cause any problems, its just the age of the tyre, it would happen to car tyres but they are normally worn out before they get to that condition, the tyres are a very strong construction and the cracks are only (normally) in the surface The old tractor would probably have a top speed of about 15 to 18 miles per hour, and even a blow out at that speed causes little problem, apart from the tractor leaning over slightly. I've experienced rear tyres bursting about three times and never had any problems controlling the tractor, the only thing that happened apart from the "bang" on one occasion the spotlight fell off the back off the tractor, blow outs normally occur after prolonged road use with some heavy machinery on the back, when the tyres have got hot. I'm sure the tractor ride would be quite safe, health and safety is enforced on farms quite strictly where members of the public are involved.
