Regarding the pull there is some information i wrote here>
http://www.mbclub.co.uk/forums/wheels-tyres/98176-definative-explination-pull-left.html
As for the tyre wear it's a little more complicated.
Line of sight?
The fast-fit industry has misinformed and misunderstood what they offer and how to apply a solution, i know this because i train them and their instructors and each time it worries me what the public had been given prior to the training and even after training i know the flow of staff within fast-fit is so rapid applied training is nothing more than a company statement!!
To the point
In my little mind it's better i train you? Not in all the technical theory and chassis dynamics, more the points that relate to this forum and members historic complaints.... So
As said line of sight, what are they offering? ( topic taken from the wim forum ) the paper is not copyright so feel free to use.
Tracking/Alignment
Is linear, this measurement shows no concern for any other angle. This form of measurement is the most common in the World and the most damaging.
Angles measured 1
Four wheel Alignment
Uses the rear wheels as a scale to centre the steering rack.... then the front toe..... this is better but is assuming the rear is centred.
Angles measured 2
Four wheel Laser Alignment
Same as above.... be wise!
Geometry/Primary
Will image the exact rear centre line to permit a centred steering wheel.. additionally the front and rear camber positions will be measured. This is the most common form of Geometry and i consider this as 'basic'
Angles measured 8
Full Geometry/primary and Secondary
Is absolute but harder to understand. Few places even with the equipment measure the Secondary angles, these include...
Castor
KPI/SJI/SAI
Scrub radius
included angle
TOOT/Ackerman
Delta curve
and so on
Most areas that involve rapid tyre wear or handling issues need to be read from the 'Secondary' data, even more important if the car has been modified or for diagnostics after an accident.
Angles measured 15+
Not easy reading indeed, millions of pounds change hands every day for 'Alignment', a need to be wise could save you £ssss
One more thing to make the 'blood boil'.. The Primary and secondary Geometry has a customer destination?
1: Primary is the '
dumb' customer version
2: Secondary is withheld unless requested and named the 'Technicians version.
..........................
Given the link to the "pull explanation" and method of measurement required we are reasonably prepared to solve your complaint.
1: The MB
DOES NOT need to have ballast installed, this is a myth or a fast-fit cop out. MB's on air suspension do need to have the level locked at mid "bump/ droop" but other than that and some fluid requirements the vehicle is unladen.
2: During the preparation parameters for a
FULL geometry the machine will ask for the ball point angles? These are the perpendicular positions of the front lower wishbone and drive shafts, the reason for this is as the suspension coils age they also sag, this change will change the dynamic position for the geometry and MB offer matter of fact positions for the static condition.
Reads overwhelming but it's not, it's a simple task within the realm of chassis calibration many manufacturers ask for.
3: If you MB had the historic pull to the left a misinformed technician may have blindly thought changing the front Toe angle away from the curb would belay the pull, this is simply not the case but typical of the fast-fit template.
4: As seen from the line-of-sight explanation above "tracking and four wheel alignment" are a conn, problem we have is most fast-fit companies and misinformed public don't realize tracking is a shared angle albeit in the right position or wrong position, this said it's symmetry cannot allow a pull.
Example
A: A correctly aligned cars front wheels in motion, looking from above would be like this | |
B: An incorrectly aligned cars front wheels in motion toed out would look like this \ /
C: Same thing but toed in / \
D: What you cannot have is longitudinal dynamic ( in motion ) toe looking like this \ | or / |
E: In the event "someone" has attempted to off-set the toe position all you will have is an off-line steering wheel, simply because as a driver you regain symmetry in order to drive forward.
Wear pattens
The type of wear is a definitive clue to the problem. There are exceptions but as a rule we have this....
1: Wear confined to around 10% of the total tyre width, front/ rear and smooth is camber.
2: Wear involving around 10% ( more if profoundly misaligned ) and rough is Toe related.
3: Wear that's smooth on the front tyres and rolls onto the sidewall is Castor related.
4: Wear on the rear tyres that ungulates up and down is Toe related. This type of wear is unofficially called "heel and toe".
Further reading
If you want to see some of the horrors i see have a glance here>
Wheels-InMotion -> Horror Of The Week
Some really good information about the MB suspension can be found here>
Mercedes-Benz: Alignment/Chassis Diagnostics from Continental Imports
My approved centres can be found here>
Buy Tyres Online UK Fitting Centres | Blackboots Wheels in Motion although if you need our support you would need to buy online.
