Tyre speed limits
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• A pamphlet giving operating-speed recommendations for goods and public service vehicles has been issued by the British Rubber Manufacturers Association Ltd. (TMC Division) and is being sent out to UK operators.
The recommendations refer to tyres inflated to the correct pressure and operating in accordance with SMMT load schedules and a foreword says it is essential to limit the maximum operating speeds of certain tyres to ensure good, safe tyre performance.
Car-size tyres on light trucks and vans are capable of operating within the statutory speed limit. But tyres on trucks and p.s.v. having wheel diameters above 15in. should not be used without consultation with the tyre manufacturer if a vehicle is likely to cover 60 miles or more in the hour. This would normally mean that any vehicle operating within the current UK speed and load regulations would be satisfactory; to average 60 mph for one hour normally calls for speeds well in excess of 70 mph.
Tyres such as those designed for on-off road use are said to be suitable for speeds of 55mph with peak speeds up to 60 mph and PT (extra tread depth) tyres for p.s.v. use can only be used safely for operating speeds up to 50 mph. On the question of remoulds, the pamphlet says that remoulded truck tyres for normal highway service can safely be operated at speeds up to 55 mph.