TECHNICAL GUIDE / 00

How to Measure Alignment and Why We Adopt the String Method

There are multiple ways to measure alignment, especially toe.

These methods, which include large alignment testers, tools attached to tires or wheels, and the string method where strings are stretched across both sides of the vehicle, each differ in their measurement principles, the information they provide, and the equipment required.

At 813 Alignment Tools, we employ the string method because it allows the operator to visually confirm the measurement setup and easily recreate the same conditions repeatedly.

What We Emphasize in Alignment Measurement

Alignment values are not an end in themselves.

In actual setups, camber and toe are adjusted, and the appropriate values for the vehicle are sought while checking the driver's feel, lap times, tire temperatures, and wear conditions.

Therefore, it is more important to be able to repeatedly measure before and after changes using the same reference, rather than just taking one precise measurement.

However, this does not mean that absolute values are irrelevant as long as reproducibility exists. To correlate results with those obtained from other equipment or measurement methods, the validity of the absolute values is also necessary.

Both the ability to repeatedly measure the same state and for those values to accurately represent the actual wheel direction are necessary for alignment measurement.

1. Alignment Testers

Alignment testers are large-scale equipment that measure the alignment of each wheel by reading targets or sensors attached to the wheels using cameras or lasers.

They can comprehensively measure camber, toe, caster, thrust angle, and more, and can output the results as data, making them suitable for diagnosing vehicle conditions.

However, they require equipment and installation space, making them unsuitable for transport to circuits or home garages. Also, since measurements are taken with tires and wheels installed, their condition is also included in the measurement results.

Wheel alignment tester that measures by attaching targets to the wheels
It can comprehensively measure multiple alignment items and diagnose vehicle conditions.

2. Direct Measurement Method

This method measures toe by attaching tools to the tires or wheels and determining their lateral or longitudinal relationship.

There are methods that combine lasers and mirrors, and methods that directly measure the distance between the left and right sides at the front and rear of the tire.

While relatively compact and portable for on-site use, it requires consistent tool attachment and measurement positions each time.

Toe measurement method combining laser and mirror
A method combining laser and mirror.
Toe measurement method measuring distance between left and right at front and rear of tire
A method that directly measures the distance between the left and right sides at the front and rear of the tire.

With methods that calculate total toe from the difference in distance between the left and right sides, it's impossible to determine which direction each wheel is pointing relative to the vehicle's longitudinal axis based solely on the total value.

Even if the total toe aligns with the target value, if the left-right distribution is uneven, the steering center may be misaligned.

3. String Method

The string method involves stretching strings along both sides of the vehicle and using these strings as reference lines to measure the distance to the front and rear of each wheel.

Since the string position and measurement points are visible, the operator can confirm what is being used as a reference and where the distance difference is being measured.

Furthermore, it allows for individual measurement of each wheel's direction relative to the reference line, not just the total toe. This enables adjustment while confirming both total toe and left-right distribution, making it easier to manage the steering center.

However, simply stretching a string does not guarantee correct measurement. It is crucial to determine the string's orientation relative to the vehicle and what it is set as a reference to.

String method for measuring toe of each wheel by stretching strings along both sides of the vehicle
Using the strings as reference lines along the vehicle's longitudinal axis, toe is determined from the difference in distance to the front and rear positions of each wheel.

Why 813 Adopts the String Method

813 Alignment Tools adopts the string method not because it is the only correct measurement method.

It's because the operator can verify the measurement state, and the same reference can be consistently replicated at the circuit or in a home garage.

In common string methods, strings may be stretched using tires, wheels, or fenders as guides. However, tires change condition due to air pressure, temperature, load, and wear. Exterior parts are also not necessarily symmetrical or parallel to the vehicle's centerline or hub position.

Additionally, the front and rear wheels may have different tread widths or wheel offsets. Simply stretching strings at the same distance from the outside of the tires or wheels can result in the strings being angled relative to the vehicle's longitudinal axis.

Therefore, at 813 Alignment Tools, we use the vehicle's hubs as the starting point for measurement, rather than tires or exterior parts.

The front and rear hub face positions are determined from the manufacturer's specified tread width and genuine wheel offset, and the string's path is set to reflect this difference.

By directly attaching dummy wheels or hub stands PLUS to the hubs and measuring at consistent positions on the product, the toe of each wheel can be determined from a reference that is less influenced by tire conditions or exterior part positions.

Absolute Values and Reproducibility

Alignment testers and dummy wheels differ in their measurement references and the elements included in their measurement results.

Back to blog