Things you need to know about: torque wrenches

Correctly tightening different parts of the bike is very important for two sort of corresponding reasons. Firstly, you want to make sure things are tight enough so that they dont work loose while you're riding. The flip side of that is that you also don't want to tighten parts of the bike up too much and end up damaging anything. Basically, there's a fine balance between not tight enough and too tight, and that's where torque wrenches come in. 

Torque is a twisting force (technically a measure of the force causing something to rotate round an axis), and it's what you measure when you're tightening any bolts on your bike. You will (or should) have noticed that every bolt on a bike has a torque rating that the manufacturer recommends and it's important to make sure that those bolts are tightened to within that range. For example, Shimano Hollowtech II cranksets have two fixing bolts on the non-drive side, and those are meant to be between 12-14Nm (that's Newton metres). 

In fact, Shimano has a really helpful torque chart on their si.shimano website where you can search pretty much every component in every groupset and find out what its torque settings are. Definitely worth bookmarking, that one. 

Park makes three types of torque wrench: clicking, beam and driver and all three are covered. They all have their various differences but, used correctly, will all make sure your bike is tightened up properly and that nothing gets damaged. Check out the below.