In earlier days when there were only aluminum bikes in those days, mechanics tend to think tighter is better when they used to fix a bike. Those bikes were all metal heavier bikes when this theory used to be fine but nowadays when bikes are going lighter and lighter with carbon frames and components the amount of torque you put into the bolts has a very important role.
Carbon is lighter and stronger but at the same time very weak as well. Take the example of a carbon handle bar. It can take a full load of a rider even on the rough surface but if you over tight it, it can break into parts on the jerk because of over tightening. And if you don’t tight it properly then, in any case, it is going to fail.
That’s why most of the parts have written a number with Nm. Nm stands for Newton Meter. Nowadays Nm is not just for carbon but for mostly all the components on bikes even if they are aluminum. It helps to prevent from damage of component because of over tightening.
So, how to do a correct torque on the bolts. There are two ways of doing it. First, you get a whole range of torque tools from 3 Nm to 15 Nm & buy a set of torque tools and use them.
Like Effetto Mariposa Torque wrench
Then you have an option of having specific Nm torque wrench set of 3Nm to 5 Nm, if you know the range just go for the specific range and you will get burzman tools.