Bolts are often tightened too much or not hard enough. Finding the correct torque is extremely hard to achieve by touch and often not recommended at all. Just picture that rear wheel axle bolt slowly coming off at a very high speed... Speaking of worst case scenarios.
Most workshop manuals mention the torque values for important bolts. That value is expressed in Newton metres (Nm). 10 Newtons correspond to 1 kg. So if something needs to be tightened to 20 Nm, this means that you have to exert 2 kgs of force on a one metre long wrench in order to tighten the bolt.
Why use a torque wrench?
The use of a torque wrench, together with the right torque, prevents three possible problems:
- Spontaneously loosening bolts or nuts, when not tightened enough.
- Warping or breaking bolts, when over-tightening parts.
- Sheared threads in bolts and nuts.
It is clear that it is important to strictly follow the tightening torque specifications - and to use a suitable torque wrench. How much play is there? With a torque wrench, you always know for sure.
Note that not all M8 or M10 bolts should be tightened to the same torque!
Many nuts and bolts are secured with threadlocker to prevent them from vibrating loose.
Be careful when using this locking compound in a blind hole: when applied to a bolt, it can seal the thread and prevent the air in the blind hole from escaping when the bolt is subsequently tightened. The compressed air in the hole can cause the amount of applied Nm to be indicated incorrectly (e.g. 20 Nm while the torque is actually lower).
This is why we advise you to apply a suitable adhesive at the bottom of the blind hole and not on the bolt itself. Of course, you should check whether the bolt makes good contact with the adhesive.