I questioned the author of the original message I was quoting, and here is his reply: Comments??
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Hello kingsway
....so you will be well aware of something called ackermann steering....for others reading here is a link that explains it
Ackermann steering geometry - Wikipedia, the free encyclopedia
....although i should point out that the first diagram at the top is factually incorrect, as no car in the world goes round corners with both back wheels inline with the line from the centre of the corner radius....if a car did do this when going round a roundabout the rear wheels would be close to the roundabout and the front one's much further away....which we all know doesn't happen in real life....they balance out....both being a very similar distance from the roundabout.
So wilki helps a bit...but keeps it simple....for a very simple reason.
The calculations to work out the perfect Ackermann system would be a fruitless waste of time....as steering angle applied by the driver could be any angle....the speed the car is travelling at would apply a different amount of centrifugal force to the rubber bushes and thus the wheel location changes slightly....the amount the car rolls on the suspension alters the steering geometry by changing the angle the steering arms and track rod ends connect to the hub carriers....and so on for ever.....so forget that and keep it simple.
Assume the car manufacturer knew what they were doing when they designed the car....and then "introduced" some error (understeer) as understeer is deemed to be safer than oversteer when novices come across it....probably because it can be "felt" through the steering wheel. (i personally prefer steering control at all times....as most things can be steered through with the aid of good throttle control)
So thinking back to when i said both wheels balance out a similar distance from the roundabout....they balance at a point somewhere in between the wheelbase.
So i set about finding where the fiesta had it's balance point.
Handbook for wheelbase and front/rear track dimensions....and then turned the steering to full lock to see how much the front wheels move forward or backward when turned....measured the wheelbase on each side of the car with the front wheels turned....and averaged the readings for the inside wheels and again for the outside wheels....and then drew to scale as best i could onto paper....mark a line from the left front wheel to the right rear....and right front to left rear....and then measure where the 2 lines cross in relation to the wheelbase centre....if in front the front wheels want packing out....if behind the rears want packing...to make the 2 lines cross in the centre of the wheelbase.
The calculations i made to arrive at the nearest spacer dimension were obtained using the co-ordinate conversion function on a scientific calculator...(years of being a sheet metal worker helped here)....and that's about it.
If anybody decides to look at this on their own car....you will probably end up finding that the manufacturer REALLY DID know what was right in the first place....and then introduced the error deliberately....because the front and rear tracks of cars are nearly always different....and when made "right" with spacers the tracks will be almost equal... and all is sorted!
Further proof Ford knew what was what comes from the hub locator....specifically it's depth....the front hubs are just enough to locate the wheel securely....the rears are made much deeper....deep enough to take the spacers and still secure the wheel securely....without having to go to the vast expense of hub-centric spacers.
However i have said "probably" i would not EVER modify a car without doing the calculations for myself....and then giving it a proper road test checking for any wayward characteristics(for definition of proper) please ask Helen 
The current shape fiesta when equipped like this is an absolute gem through corners....and i have owned a number of 200+ horsepower performance cars in my time....it "sets" itself into a corner with such ease and accuracy it must be one of the best cars handling cars in it's price bracket.
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I then said 'Okay, so it improves handling - but does it have any real effect on rolling resistance and FC'....
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Yes definitely....reduced error in the tracking improves tyre wear and fuel consumption...although i do not have figures to prove that....i can easily tell the increased willingness to roll on full lock....which simply must mean reduced effort required to move the car....have you ever heard cars in car parks going very slowly....but squeeling the tyres?...this is what causes it.
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I'd have thought we spend so little time with wheels turned, that any differerence would be un-noticeable?