Wheel alignment using the BMW E36 as an example

The E36 model (the 3 Series BMW) was chosen because it uses a developed form of the multi-link rear suspension first adopted on the Z1. The E36 front suspension has a lateral control arm (a lower wishbone) and a suspension strut. A stabilizer (anti-roll bar) limits body roll when cornering. The resilient wheel locating pivot is mounted on the outer end of the lateral control arm. The E36 rear suspension consists of a rigid trailing arm linked to the wheel carrier and two lateral control arms, one above the other. To improve insulation from driveline and rolling noise, the trailing arm has a resilient mounting on the body. A special feature of this design is the very small variation in toe-in when the suspension moves in the vertical, longitudinal or lateral axis.

Preparatory work and condition of car

The specific preparatory work needed on the E36 is:

If the car is within the tolerance of +/- 10 mm, vary or increase the load to correct its height to within +/m 1 mm of the desired value specified by BMW.

Measurement before adjustment

Like the subsequent adjusting work followed by the measurement after adjustment, this work can take place under program control or as a free-choice procedure.

Program-controlled measurement

The software determines the order of vehicle measuring points called up in the program-controlled measurement mode, and controls the procedures. For each measuring point the appropriate screen graphics are displayed with the target and actual measured data for comparison. The entire measurement procedure is controlled by the "Program step forwards" and "Program step back" keys.

Free-choice measurement

In this case the operator can choose the measuring points in any desired order. The desired measuring point can be selected by applying the sensor pen to the digital keypad on the screen.

When free-choice measurement has been selected, certain measurements have to be performed in the correct order in order not to falsify the results.

For this reason, wheel alignment in the free-choice mode should only be attempted by workshop personnel with suitable prior knowledge and ample experience.

The individual stages in before-measurement adjustment are:

If out-of-tolerance values are found, renew damaged components and/or perform the necessary adjustment work. All values that are adjustable on the E36 are marked with a tool symbol in the "Target values" column of the measured value summary. The appropriate pictures and written instructions for adjustment work can be called up on the screen by pressing a key.

Adjustment work

The individual steps in adjustment work are:

Measurement after adjustment

The individual after-adjustment measuring steps are:

Data print-out

The report printed out by the integral A4-format printer is divided into three zones:

The data in the "Before adjustment" column show the condition in which the vehicle was received. Measured values beyond the permitted tolerances, which therefore need adjustment, are marked here by an asterisk (*).

In the "Target data" column, all available specified values with their tolerances are listed, and in addition the maximum permissible tolerance between the left and right wheels is stated.

If no target values are specified for a particular measured value,. a "#" sign appears in this line of the print-out.

In the "After measurement" column, a note appears of all measured values which were determined in a second complete measuring routine after such adjustment work as was necessary.

If adjustment work was correct and all measured values are then within the permitted tolerances, no further "*" symbols should be seen in this column.

The complete wheel alignment report sheet, with the identification data in the header, is saved on to the wheel alignment computer's hard disk after printing out, and can be called up again with the aid of the relevant search criteria if queries arise, displayed on the screen and printed out in A4 format.

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