Umwerfer

Manufacturers recommend using complete groupsets to get the best performance from their components. However, it can be possible to replace Shimano road group components of the same generation, such as Dura Ace 9000, Ultegra 6800 and 105 5800. (A 105 5800 front derailleur could be substituted for a Ultegra 6800 front derailleur). There may well be other examples of cross compatibility, although when you try to mix between manufacturers this is less likely to work because different manufacturers use different amounts of cable pull for shifting.

To fit a braze-on (not clip-on) front derailleur to a frame without a braze-on / tab, you will need a front derailleur / mech clamp. Front derailleur clamps are available in different size options to fit most frames - 28.6, 31.8 and 34.9mm. These sizes correspond to the diameter of the frame seat-tube.

We always recommend following manufacturers instructions for fitting any component. The Youtube channels of Park Tools and GCN Tech have very indepth and comprehensive advice for completing all sorts of jobs on bikes, these are also worth watching particularly if you are inexperienced or unsure.