Brands like Canyon are delivering their bikes with torque wrenches that are based on the torsion resistance of the metal that mades up the wrench, like the one pictured below (for the working principle).
To describe it simply: once the bolt is ready to be tightened, applying torque will twist/deform the metal proportionally to the torque. A needle and gauge allow a measure of the deformation, and hence the torque.
Given they only cost a fraction of more professional wrenches, a tool like this would be relevant in the toolbox of those who do their maintenance themselves. I'm wondering how "good" they are:
- does the torsion characteristic of the metal evolve over time or with temperature, of if "abused"?
- do they offer a level of accuracy that is compatible with torque-sensitive applications, such as the tightening of a carbon seatpost?
- what are the attention points when buying one?
What would be the pros and cons compared to a more traditional torque wrench?