Product Reviews - August 14, 2014
The maintaining of the modern motor vehicle is no longer a hit and miss situation and a greater degree of attention needs to be paid to the manufacturers specifications and the effects that working outside the specifications can have on the components of the car. A good place to start is to recognize that different car manufacturers may have different specifications for similar components and that all motor vehicles are not the same therefore each make of vehicle must be approached with a knowledge of what the manufacturer has specified.
The specifications placed on wheel nuts are very much overlooked and an assumption that all wheel nuts are tightened at the same level is a very common problem. As most workshops use air impact guns to tighten the wheel nuts, the chance of over or under tightening is very high as the level of torque being delivered by the impact gun is generally unknown. Incorrect torque and sequence of torque application causes such problems as distorted rotors, out of balance wheels, broken or fractured wheel studs, increased tyre wear caused by misalignment, increased rotor and disc pad wear, fractured alloy wheels leading to total failure of the wheel, cracks around the stud holes on steel wheels, not to mention the fact that changing the wheel on the side of the road is almost an impossibility.
The car manufacturers have placed specific tolerances on the loads applied to wheel nuts, this being calculated taking into account the clamping load required to hold the wheel in place, the stud size, the material the wheel is made from (it is quite common for different torque values to be specified for alloy and steel wheels on the same vehicle) and a variety of other aspects. Once we move outside those parameters specified by the manufacturer, all sorts of strange happenings take place. If a wheel nut is under torqued, the wheel can work loose creating out of round stud holes, damage to the studs and the wheel can actually come of the car. If the wheel nuts are over torqued, it can have disastrous effects on the operation and function of the cars components.