All work on the car has been done by the Porsche Classic Centre Son, a great place just outside Oslo specialized in classic Porsche only.
Since i am a noob I would first doubt of my capability to properly describe the issue :-)

When I picked up the car, right away I did not notice anything, after some days I started noticing something i never did before.

Let's say I am going straight and I decide to turn right, the wheel would feel hard to turn for the first few degrees and than would get very light with a tendency to keep pointing in that direction by itself.

If while going right I then proceed to steer in the opposite direction, same again, at first heavy steer with a feeling of the car wanting to keep going right, than suddenly light and keeps steering left.

I thought at first might be something with the power steering, like, sorry for no better expression "it would start working with a bit of delay"

 

This is a good description of either or both front and rear wheels with too much toe.

Too much front toe occurs when the 928 is lifted before or during alignment. The suspension will not settle on the alignment rack. Thus the ride height is too high when the alignment is performed. Over the next 50-100 miles the suspension settles to the lower, normal ride height, and the front toe goes far positive.

The 928 is almost unique among all cars, in that it will not settle (even on slip plates) after being lifted off the suspension.

This is a well documented issue - in the workshop manuals - that 928 owners know about but no shops or dealers - even “Porsche Classic dealers” will believe this and all will raise the car to make it easier loosen bolts.

But, since it defies “conventional common sense” few 928 owners actually believe it until they’ve destroyed a couple sets of front tires.

Now that your 928 has settled, take it to a shop that just does alignments and have them record the current alignment settings and do so without lifting(*) the car *at all*.

* Lifting the car means unweighting the suspension NOT lifting the entire car on the alignment rack when the weight is supported by all four wheels.

 

A generally good post that many listers will not be aware of [but not this one]- whereas i have no doubt you well aware of the concept I trust you understand that understeer is a condition not a cause. You have itemised three possible causes that lead to understeer- the term itself refers to a condition wherein the front grip is less than the rear grip so the car tends to drive straight on rather than go where wanted when the car is on the limit of adhesion- thus the term's origin.

Now perhaps I can suggest you read once more what the OP actually posted [that I quoted] and therein he describes typical understeer behaviour. What he possibly does not understand is why when he lifted off the gas the rear end remained planted- that is the Weissach axle doing its job to help prevent lift off understeer- that is also typical behaviour for a 928 running stock wheels but most certainly atypical for most other cars of that era.

 

Thank you for your advice. Once winter is over I will for sure have the alignment checked again with no lift.

 

This is really interesting. When I tried to do some mid turn lift off, I wanted to see if the rear would move.
I wasn't expecting it because the engine is in the front and normally the car would just pretty quickly regain front grip.

But it seams quite easy to make it lose front grip by staying on the throttle, hence my question in opening this thread on how to balance it a just bit more cause the car feels immovable in the back and light in the front even with a big engine in the front.

At my level of experience with my 928, outside of a track, I don't feel comfortable tossing the car into a turn, so probably my speed entering into a a corner is lower than it could be, which means I don't notice as much "type 1" understeer but i like to stay on the throttle and pushing after mid turn so i notice the ease of losing the front, which is exactly what I would like to improve a little to "feel the car a bit more balanced"

My guess was going same tire size all around might do it, but it might not and I would just be throwing time and money.

 

A well aligned 928, matched with complementary springs/shocks and decent (Continental DWS, less than 5 years old) is hard to shake on public roads.I know we're talking track here but want to put my 2 cents in...I have an off ramp that has a pretty sharp turn to the left, it's also elevated so you're going uphill for part of the turn and downhill for the other part....within the turn are multiple joint seams....I have yet to shake the back of the car so it jumps outward when driving over the joints (towards where gravity would push it). Thoroughbred.

My 2020 Subaru WRX (no slouch, with it's own racing pedigree), with Eibach springs and Dunlop summer only tires (240 treadwear...basically gumballs) at the same speed always jumps outward when hitting the joints....the 928 even today does things better than brand new metal...even competent machines like a WRX (this is my 2nd and on a side note they're delightfully simple to modify...)

The engineering within the Weissach design is still game changing...even today....this car is basically floating down the road and you hit a turn and expect it to do the thing most mushwagons with a similar ride would do when presented with a curve...but this car hunkers down, the back end tucks itself in and before you know it you are sailing through this curve like you're driving something with a much less forgiving ride. I have original bushings all around...new ball joints everywhere and our custom Eibachs with 17" wheels...that's about it....Car has been garaged all it's life and today it's in an AC/heated one; probably the reason the suspension still works as well as it does. No doubt it would benefit from a bushing refresh...I'd go with standard rubber....made the mistake of going all polygraphite on another car and ride became way too harsh...

KC has a shop that does the heavy lifting on my car...they do alignments and I always feel a positive difference in how the car drives when I get it back; they understand the car and the shop owner regards the 928 as a magnificent car. PM me for details if you want their contact info.

 

What you are describing is more or less identical to what I experienced nearly 20 years ago. When you start pushing the envelope you enter "new territory" and on lower speed bends in particular you quickly find how weak the front end grip really is probably because one is more confident to throw it into the slower bends harder. The other "problem" that becomes apparent is that the 928 is very adept at trail braking so one ends up going deeper into the bend whilst still on the brakes and the stock mod to enhance this feature is to fit a higher pressure rear bias valve.

In an attempt to overcome the understeer issue Louie came up with his adjustable rear links that were intended to provide a 5 minute track side adjustment to reduce the understeer and this is achieved by reducing the leverage on the rear sway bar thus making it a bit stiffer. Not sure if they still available at all- I think Hans made a batch not long ago. The CS wheels then became popular with track junkies because with 8 inch front rims they could carry a 245 section like the rears so 245's all round became popular.and [as I recall] that spurred on development of the Devek adjustable front sway bar- this would be pointless on a stock setup.

At some point folks started experimenting with wider wheels and if you have seen Adrian's thread on his recently acquired CS, he has also talked about a developmental race car. This car was a works racer in all but name and as I understand it ran front 9.5 inch wide wheels with ET68 and 10 inch rears with ET60. With that combo one can run a 265 up front and a 285 [or wider] on the rears [what I have used for the last 17 years]. If you look carefully at the photo's Adrian posted of this car one can see quite clearly that the upper and lower control arm bushes were modified to carry rose joints amongst many other features.

Not difficult to see what a slippery slope this becomes! The 928 was never designed to be a sports car yet alone a race car but it has a lot of potential in that direction.

 

Very debatable.

Not debatable at all.

And, the first thing to do is to get more meat in the front. And I know I’m preaching to the choir.

The best money I’ve ever spent on a 928 are 3-piece Fikses running 9” w/255 front and 10” w/265 rear. More meat up front transforms the way the 928 works. Better feel, better braking in any weather, better turn-in, less plow (catastrophic understeer.) To this day, when I drive a 928 with 225s on the front it feels like I’m on bicycle tires.

 

Once one has driven the 928 with sensible rubber up front there is no going back. I currently run with 255 on the fronts and 285's on the rear. The difference between 225 and 255 up front is night and day and it is as though the gain in front traction is disproportionately high . If I were to try and run with a same size section on the I reckon it would be somewhat tail happy. The Louie rear links and the Devek bar besides their main intent also have another advantage in that they permit adjustment of the drop links to eliminate any pre-tensioning. With the Devek bar set at roughly the midpoint the handling feels "neutral" but that may also be in part me hitting the chicken switch earlier than I did 20 years ago! Whatever, the car is remarkably well planted and I always recommend quality rubber not that i have a lot of choice over here.