Before installing the front derailleur, the first thing you have to do is to identify the type of front derailleur you have. You need to have to check at how the cable pulls, size the clamp diameter, determine the cage length if short or long, and of course count the number of shifts, 2 or 3. Establish the fit front derailleur you require, make sure you have the correct fitting. The next thing is to gather all the tools necessary along with the instructions from your manufacturer.
Now you can start to install the front derailleur.
With a low direct mount model, you need to remove the crank to access the mounting points while the E-type front derailleurs require you to remove the drive side crank bearing and replace one of the spacers with the mounting plate.
During the installing of the derailleur, you have to pay attention to the following point: the gap between the top of the large chain ring teeth and the lower edge of the derailleur cage should be 1-3mm, regardless of design. Use friction grease to reduce the necessary torque on the clamp. Tighten the clamp and make sure the cage is parallel with the chainring.
Step 1: Firstly, bolt the E-type derailleurs down with the single alignment bolt, and then torque the bearing cup back in place.
Step 2: it is not difficult to set the gap with a 2×10 derailleur. Just align the set height and torque, note that everything should keep parallel. The 3×10 setups require you to either use a “pro alignment block” that comes with new Shimano front derailleurs or you can carefully move the cage to the middle ring position and check the gap, adjust up or down as necessary. Torque the clamp down based on your manufacturer’s recommendation (usually 5 – 7Nm).
Step 3: Now you can set the low (L) and high (H) settings. With the chain already installed you want to have a 0.5mm gap between the inner chain guide plate and the chain. If you don’t have a chain on, from the side of the small chainring to the inner chain guide plate you want a gap of 1.5mm.
Step 4: Turning the (L) screw counter-clockwise increases the gap while turning the screw clockwise decreases the gap. With the high gear, we want the same spacing of 0.5mm between the chain and the inside of the outer plate. Use the (H) screw this time – a clockwise turn will decrease the gap.
With the derailleur physically set up, now you can continue with the rest of the installation.