eli5 How are torque specs determined for various parts on a car? And what would happen if you increased them by something like 25% across the board?
In: Engineering
The required strength of the mechanical joint versus the strength of the fastener and the materials being joined. For areas with significant dynamic loads, vibrations and fatigue are taken in to account.
Increasing the torque beyond the spec for a fastener can cause the fastener or surrounding materials to fail. For example, if you over-torque a bolt, it will permanently deform, weakening it because it becomes thinner. You might also crack surrounding materials.
Usually, there’s a large safety margin between the spec torque and the point at which the joint will fail. After all, torque is a proxy for the holding power (tension) of the bolt. Various factors, such as the friction between the threads and the accuracy of the torque wrench can affect the actual load applied when installing a fastener. Whether there will be an issue with the car if you increase all torque by 25% is hard to say. Usually the margins (if given) are around 10% of the specified torque, but the actual point to failure is likely much greater than that. For a lot of publications, such as engine repair manuals, there isn’t a margin given, but only a single specified torque.
Latest Answers