Naturally, as a torque solutions provider and torque tool manufacturer this is very concerning and our fear is that the issue is not given its due attention by the road haulage and public service vehicle industries where speed and low cost often seem to be the most important factors in wheel bolting.
It’s very important that maintenance engineers know that wheel nut movement indicators and nut locking devices are no substitute for good bolting practice, including the correct application of torque to wheel bolts.
Plastic wheel nut movement indicators can be applied to commercial vehicles, such as articulated lorries and buses, to indicate movement in the wheel nut. Many commercial vehicle users also apply nut locking devices which link two or more adjacent nuts in such a way as to prevent them from undoing.
Wheel nut movement indicators are an excellent warning system to visually alert a driver, transport manager or mechanic that there is a potential problem with the wheel nuts. Equally, locking devices can serve a purpose in helping to retain the initially applied torque.
However, the indicators and locking devices are not a substitute for good bolting practice which includes ensuring that the threads are undamaged, clean and free from rust and paint. Vehicle manufacturers’ recommendations for thread lubrication should be strictly adhered to and the correct torque should be applied using a calibrated torque tool.
We regularly come across situations in both car and heavy vehicle garages where the wheel nuts are over tightened with an impact wrench before the torque wrench is applied for the final tightening.
We would always recommend that wheel nut movement indicators should only be fitted once this good practice has been applied. The same is true of locking devices but they should not be used as a substitute for the regular wheel nut re-checks that are required by law.
Philip Brodey, Sales and Marketing Director, Norbar Torque Tools