Estimating Caster Using a Digital Camera

Harvard wrote:
This is a method estimating the front end caster using a digital camera and using Windows Paint to estimate camber angles from the picture.

Normally one would take 2 pictures from each wheel, one full left and a second full right. For this approximation we will assume both wheels are identical and simply use one camber picture from each wheel when the steering wheel is cranked full right.

This first picture is taken in line with the outside of the drivers side wheel and measures a camber of NEGATIVE 2.5 Degrees.


This second picture is taken in line with the outside of the passengers wheel and measures a camber of PLUS 3.5 Degrees.


This picture is taken with the camera resting on the drivers side fender and captures the drivers side wheel to be cranked about 30 Degrees to the right.


This picture is taken with the camera resting on the passengers side fender and captures the passengers side wheel to be cranked about 33 Degrees to the right.


The estimated CASTER (K) is found as:
K = ( 180 / pi ) * ( ( C1 - C2 ) / ( T1 - T2 ) )

Where:
C1 is the +CAMBER when the DS wheel is FULL LEFT or the PS wheel is FULL RIGHT.
C2 is the -CAMBER when the DS wheel is FULL RIGHT or the PS wheel is FULL LEFT.
T1 is the +TURN ANGLE when DS wheel is FULL LEFT or the PS wheel is FULL RIGHT.
T2 is the -TURN ANGLE when DS wheel is FULL RIGHT or the PS wheel is FULL LEFT.


In this case:

K = (180 / pi) * ((+3.5 - (-2.5)) / (+33 - (-30)) )
K = 57.32 * (+6.0 / +63) = +5.5 Degrees

You do realize that the camera lens is going to severely distort your photos?

This effectively skews the perceived angles and bending things in your photos. Camera lens are not linear at any distance, the effect gets much worse when taking extreme up close or far way photos. Some lenses are better than others but since a lens bends light as a primary function there always will be errors..

It is best to leave this to a properly equipped shop if you don't wish to take your life in your own hands..

On edit..

Perhaps you will understand what I am talking about with the following pix as and example of a camera lens "bending"..



Please note, the item in that pix is FLAT but yet the error from the lens doing its job has BENT the item..

Also note worthy is the angle and height from object can majorly skew the pix..