Wheel Alignment

[Tony-Bones]

Front wheel Alignment is the direction of the front wheels relative to the rear centre line (Thrust Angle) if the thrust is centred then the Dynamic toe position will conclude the designed drive, the force is lateral.

Chassis Dynamics

The complexities of toe seems endless, and they are, lets examine a few examples... Remember this is 'Front toe only'

Drive train Dynamics

1:Front wheel drive is pulling the car compromising all the bushings enabling toe in.

2:Rear wheel drive is pushing the front wheels then reacting to the bushings enabling toe out.

3:Both drives acquire reactions measured by the rolling resistance of the tyre.

4:Both are subject to 'Down-force Aerodynamics'.

5:Both are dependant on tyre width.

6:Both are dependant on tyre silica content (Grip -ve- temperature range -ve- displacement -ve- pressure)

The Front Toe is calculated static in measurement to accommodate the dynamic reactions mentioned above, but the maths fall short of absolute, so an (average position) of the toe is projected. There is a method to simulate the Dynamic flow static but this is rarely observed. (Another thread maybe)

Maths

It is assumed that a RWD car will have an average thrust/rolling/braking/aero percentage, add to this the ideal tyre width and pressure then a static position of +8' per wheel can be born, this then would assume the average dynamic package will realise a 0 toe percentage, the only constant here is the promise, reality suggests the toe positions revolve within a constantly changing three dimensional environment so is subject to testing and re-testing to conclude the cars current level of wear within the chassis. A matter of fact (position) is misleading to the extreme.

wim says

All that is exampled here is the intentions of the manufacturer to possibly assume a 0 toe dynamically. Fast fit rape front wheel alignment blaming it for every problem offered by the customer, be wise! Very few chassis engineers could conclude the toe position in an absolute format although Geometrically it's the most simple angle of then all.....

Considering this is the simplest angle of over 15 angles then now you can understand why tyre wear is such an issue for the Lexus, to find understanding seems a challenge hence this post, tiss better to be educated in advance..... Bullets in your gun type of thing?