What is a Dummy Wheel? What it can and cannot do

Differences from regular wheels

When measuring alignment using regular wheels as a reference, measuring instruments are applied to the wheel rim or tire sidewall.

With this method, wheel runout, damage, tire deformation, internal pressure, and the position where the measuring instrument is applied can all affect the measurement results. Also, with the wheels installed, it can be difficult to access adjustment points like arms on some vehicles.

A dummy wheel attaches directly to the vehicle's hub, using a surface or measurement point provided on the product as a reference. Since it bypasses the tires and wheels, the measurement standard becomes clear, and it becomes easier to access the suspension adjustment points.

What can be done with a dummy wheel

Camber measurement and adjustment

An angle gauge is applied to the angle measurement surface provided on the dummy wheel to check the camber angle.

Measurements can be made using a pre-designed surface as a reference, and because the wheels are removed, camber adjustment points are easily accessible.

Toe measurement and adjustment

A toe adjustment tool is attached to the dummy wheel, and a string line is stretched using the hub as a reference.

Using the distance between the string line and the hub as a reference, toe is checked from the difference in distance at positions corresponding to the front and rear of the tire when viewed from above the vehicle.

Suspension adjustment in 1G state

With the dummy wheels installed on the vehicle, arm tightening, ride height, camber, toe, and other adjustments can be performed.

The positional relationship of the arms and the condition of the bushings differ between a jacked-up state where the suspension is extended and a 1G state where the vehicle bears its weight. Being able to access adjustment points while supporting the vehicle in a 1G state is one of the main purposes of using a dummy wheel.

Re-measurement after setup changes

After changing ride height, springs, arm length, etc., alignment can be re-measured on the spot.

Especially at circuits, settings can be changed between driving sessions, and the effects of those changes can be observed within the same day.

If the vehicle is moved to a shop for modifications and then driven again later, conditions such as temperature and road surface may change. By performing measurement, adjustment, and re-driving at the track, it becomes easier to ensure consistent comparison conditions before and after setup changes.

Where are dummy wheels used?

Dummy wheels are mainly used in the following environments:

• Race vehicles undergoing setup changes at the circuit
• Shops and teams that continuously adjust suspension
• Individual users building a measurement environment in their home garage
• Vehicles where adjustment points are difficult to access without removing the wheels
• When you want to manage vehicle condition and setup change history

For individual users who only adjust to standard values once a year, it may be more reasonable to ask a well-equipped shop to do it.

On the other hand, if you frequently change suspension specifications, check conditions before each run, or make adjustments at the circuit, having the ability to measure and adjust yourself becomes significantly more important.

Benefits of using a dummy wheel

The value of a dummy wheel is not just its ability to support the vehicle with the wheels removed.

By establishing a measurement standard on the dummy wheel directly attached to the vehicle's hub, and measuring with the same vehicle, tools, installation method, and work procedures, it becomes easier to compare values before and after setup changes.

Additionally, easier access to adjustment points shortens the time required for measurement and adjustment. Standardizing work procedures also reduces the reliance on individual mechanics for on-site work and is expected to alleviate their workload.

Peripheral equipment required for measurement

To measure toe and camber, in addition to dummy wheels, you will need an angle gauge, string line (fishing line), and a laser level.

• Angle gauge: Used for measuring camber angle
• String line (fishing line): Used for measuring toe
• Laser level: Used to create a level installation surface using a surface plate

Specific equipment will be compiled separately as "Equipment Required for Alignment Measurement & Recommended Purchase List."

Conditions to check during measurement

During measurement, check and standardize the following conditions as much as possible:

• Height and inclination of the surface where the 4 wheels are placed
• Fuel load
• Suspension condition after jacking up
• Steering position
• Adjustment points for each vehicle
• Measurement position and work procedure

Differences between Dummy Wheel and Hub Stand PLUS

Both are tools that support a vehicle with the tires and wheels removed, allowing for suspension measurement and adjustment. However, there are differences in their structure, specification determination, measurement standards, and the types of work they can handle.

A dummy wheel is a highly specialized tool where PCD, number of holes, hub center height, etc., are set according to the vehicle and application, and it incorporates camber and toe measurement standards. It can also be designed to accommodate multiple PCDs in one product.

The Hub Stand PLUS is a product with an easier-to-introduce configuration, creating an environment for suspension adjustment and alignment measurement with the wheels removed.

Which is more suitable depends on the vehicle used, measurement method, adjustment frequency, required specifications, and budget. The detailed differences are explained in a separate article, "Differences between Dummy Wheel and Hub Stand PLUS."

Cases where introducing a dummy wheel is beneficial

The following cases are likely to benefit from introducing a dummy wheel:

• Frequent changes to suspension specifications
• Wanting to measure and adjust at the circuit
• Wanting to compare before and after changes on the same day
• Wanting to easily access adjustment points
• Wanting to shorten measurement and adjustment time
• Wanting to reduce the workload of mechanics
• Wanting to reduce the reliance on individual expertise in on-site work
• Wanting to continuously compare vehicle changes
• Wanting to share the measurement environment and work procedures within a team

On the other hand, if you don't perform measurements or adjustments yourself and the measurement frequency is very low, it might be more rational to request services from a shop.

Summary

A dummy wheel is a tool that supports a vehicle with its tires and wheels removed, allowing for alignment measurement and suspension adjustment in a 1G state.

Its role is not merely to support the vehicle. It's about establishing measurement standards from the vehicle's hub and creating an environment where measurements and adjustments can be repeatedly performed while adjustment points are accessible.

Dummy wheels vary in how measurement standards are set, their structure, and how specifications are determined depending on the product. The next article, "7 Points to Check When Choosing a Dummy Wheel," will explain the key considerations for comparison and selection.