I've just bought a new bike at Ochnersports.ch. It came with the front derailleur completely un-fitted so it wasn't possible to change the front gearing.

This is the first time I bought a bike with such low class of equipment, Shimano 105. Well, I read that overall it's a good class (!) though might be just heavier than Shimano Ultegra with which I am familiar. The bike overall weight is 8.4 kg so I said to myself, that's ok.

I service bikes myself so also this time I would prefer to do it instead of fighting with the shop and risk that they might screw something else during incompetent servicing.

I tried to adjust it following this guide https://www.youtube.com/watch?v=9zZWAUp6oOE

Unfortunately I cannot get it fit for both edge positions without any scratching. I was able to make it reasonably fit where the chain is just slightly scratching the derailleur in both edge positions. I'm really left with doubts, is it just the quality of Shimano 105 class, or something else is wrong. Maybe the cable is wrong, too stiff or something? It seems to be perfectly fitted (the high/low limits) if only I help it with a little push with my finger, so it's like the spring is too weak or the cable too stiff.

At this moment I regret buying bike with Shimano 105 equipment, but I hope I'm wrong about it.

I'm going to look for a more suitable forum, but thanks for any "professional" advise. I'm sure there are also DYI bike geeks here

Shimano 105 groupset is a really solid one, you shouldn't have any problems or whatsoever.

By "both edge" you mean cross-chaining e.g. smallest sprocket with smallest chainring? Or smallest sprocket with largest chainring?

I always adjust my shifting by following Calvin's guides from Park Tool, they really are superb!

https://www.youtube.com/watch?v=ZNG7g83lI-s

105 is perfectly good stuff, unless you need competition level bits.
Whilst cross chaining (tsk, tsk) you might have issues, but there should be a click of minor adjustment in the gears.

The one time I screwed up a front derailleur it was due to it being slightly rotated on the z axis, and then when adjusted it rubbed quite a bit until I straightened it up.

Anyways, cycling etiquette states that you must be in the big ring at all times.

Rule 90 // Never Get Out of the Big Ring.If it gets steeper, just push harder on the pedals. When pressed on the matter, the Apostle Johan Museeuw simply replied, “Yes, why would you slow down?” It is, of course, acceptable to momentarily shift into the inner ring when scaling the 20% ramps of the Kapelmuur.

And more generally, Rule No. 5 applies

Oh, by edge cases I meant:
1. high front + smallest rear
2. low front + biggest rear

For some reason I can't get it right to avoid (both at the same time):
case 1. chain scratching right edge of the derailleur
case 2. chain scratching left edge of the derailleur

In both position there should be still a little gap (~0.5 mm) between the chain and the derailleur after shifting. I can achieve that if I push the derailleur by hand after shifting, so clearly something doesn't move fluidly enough

Ok, later I'm going to move it a bit up to 2-3 mm, as mine sits about 1 mm above the teeth, and I'll double check if it's parallel to the teeth.

You could do worse than read up the best source of cycle maintenance information available on the internet, that of the late lamented Sheldon Brown. Simply the best, in my view.
https://sheldonbrown.com/front-derailers.html

Today's Shimano 105 is great, it's almost Dura-Ace/Ultegra in terms of function, it often uses some heavier pieces in places which makes it cheaper.


The shift lever will let you move between the two chainrings with a big throw but normally you can also make a micro adjustment with the lever when the chain rubs, it's a small click in each way.



This video has some specific help for the R7000 105 front mech: https://www.youtube.com/watch?v=9zZWAUp6oOE

I got it working, quite well!

Adjusted the height tan everything else as on this tutorial https://www.youtube.com/watch?v=42bSAnk9_zQ

^^ There's nice tip how to achieve correct tension of the cable in that video

Happy days! Enjoy riding!