Re: Confused about camber and toe
The first question, is where does the tyre wear take place on your car? The inside edges, outside edges, or the centre of the tyre?
I'm not familiar with the 166, nor am I that familiar with the terminology used in the settings you have been given, so I could be talking gobbledegook here as a result! Nevertheless, my thoughts are as follows:
1. "Toe" is the term used to describe the way the wheels point when viewed from on top. "Toe-in" means that the leading edge of each tyre points INWARDS towards the vehicle centreline. Although notations seem to vary, it is typically expressed as a positive number of either degrees, or millimetres at the wheel rim. "Toe-out" is the opposite - i.e. the wheels point AWAY from the car's centreline. Usually expressed as a negative number.
If a car toes IN by (say) +2mm, it means the distance between the leading edges of the two front wheel rims is 2mm SHORTER than the distance between the trailing edges of the two front wheel rims (measured at the height of the centre of the wheel).
2. "Semi-toe" is not a term I've seen used before, but I guess it means the distance from each rim to the centreline of the car rather than the opposite wheel. In the example above, the "semi-toe" would be +1mm per side of toe-in.
3. On front wheels, "Semi-toe" is, I think, a pretty meaningless concept because to make the car go in a straight line, the steering wheel will just sit at whatever angle it needs to sit in order to ensure that half of the total toe is on each front wheel! On the rear wheels, "semi-toe" is extremely important, because they can't steer, so if there is more on one side than the other, the car will be always trying to steer a little bit from the rear. It goes without saying that the rear "semi-toe" should always be the same on each side!
4. I have a 164. These are supposed to run a bit of toe-OUT on the front wheels. This is an old trick to make a nose-heavy front wheel drive car "turn-in" nice and crisply. It works but tends to promote tyre wear on the inside edges of the front tyres. Toe IN tends to do the opposite. I tend to run the minimum amount of toe-OUT possible (or even slight toe-IN) to even out the tyre wear. The disadvantage is a very slight vagueness of the steering in the straight-ahead position but it's barely perceptible!
5. Camber is the way the wheels lean when looking from the front or rear of the car. If they lean in at the tops, that's NEGATIVE camber and if they lean out at the tops, that's POSITIVE camber. Most cars run a bit of negative camber. As the car rolls in a bend, it tends to help the outside tyre (the one doing most of the work) to keep it's contact patch at 90 degrees to the road surface so that the biggest footprint is available. Running a lot of negative camber obviously also gives the inside edges of the tyres a hard time but NOT (in my experience at least!) as much as running toe-out. Obviously, with wide, low profile tyres such as the ones you're running, camber settings are far more critical than the 205 55s that my 164 runs, because the tyre is narrower and the sidewall is deeper so the tyre carcass can absorb the camber angle more easily whilst still keeping the contact patch flat.
Are 166s supposed to run that size of tyre? If not, it would be worth going back to Alfa's originals to reduce tyre wear.