TECHNICAL GUIDE / 02

7 Points to Check When Choosing a Dummy Wheel

1. Are the measurement standards clear?

The first thing to check is where the dummy wheel is designed to measure camber and toe.

Camber measurement requires a surface to place an angle gauge. Toe measurement requires a setup where a string line can be stretched from the hub as a reference, and the difference in distance between the positions corresponding to the front and rear of the tire can be read.

Points to check

• Is there a surface for measuring camber angle?
• Are the reference positions for toe measurement clear?
• Can angle gauges and scales be placed stably?
• Can the measurement position be used under the same conditions every time?

Merely being able to support the vehicle does not constitute an alignment measurement standard. It is necessary to check whether the design includes the measurement method.

2. Are the static shape and deformation under load considered?

For dummy wheels, it is necessary to check not only their shape before being installed on the vehicle but also their deformation when under vehicle weight.

A product's shape is determined by its manufacturing method, number of parts, positioning method, joining method, and so on. When multiple parts or joints are involved, dimensional differences between parts and assembly misalignment must also be considered.

Moreover, not breaking and maintaining measurement standards under load are not the same thing. In addition to strength, rigidity, which is the resistance to deformation under load, is also important.

Points to check

• What determines the position of parts relative to each other?
• How many parts or joints are involved up to the measurement standard?
• Is the required dimension inspected in the finished state?
• Is the designed load per plate indicated?
• Is deformation under load considered?

The differences between machined, bolt-assembled, and welded structures are explained in detail in "How Alignment Tools Create Measurement Standards."

For measurement criteria and rigidity related to measurement results, please also refer to "Criteria, Rigidity, and Measurement Conditions that Affect Measurement Results."

3. Is the hub center height suitable for the application?

The hub center height is the height from the ground to the center of the hub when the dummy wheel is installed.

For normal tires and wheels, the hub center height is approximately half the tire's outer diameter. If you want to reproduce the actual tire installation state, it is determined based on the outer diameter of the tire to be used.

On the other hand, for prioritizing workability on a circuit, it may be set lower than when actual tires are installed. In such cases, the specifications are chosen after deciding the amount and purpose of the reduction.

Points to check

• Tire size to be used
• Should it be the same height as the actual vehicle?
• Should it be set lower for workability?
• Are the front and rear tire outer diameters different?
• Will it be shared among multiple car models?

The hub center height is an important specification that determines usability and compatible vehicles. Detailed methods for determining it are explained in "How to Determine the Hub Center Height of a Dummy Wheel."

4. Can it be properly secured to the vehicle?

Since dummy wheels are directly attached to the vehicle's hub, suitability cannot be determined by PCD and the number of holes alone.

Points to check when ordering/selecting

• PCD
• Number of holes
• Hub diameter
• Diameter of hub bolts or wheel bolts
• Interference with hub, brakes, and suspension parts
• Warranty if installation is not possible with specifications communicated in advance

Before introduction, confirm what information the manufacturer uses to verify suitability. It is also important to ensure that if installation is not possible despite correctly conveying the specified vehicle information, you can receive a warranty for corrections or remanufacturing.

If sharing among multiple vehicle models, simply increasing the number of compatible holes is not always the answer. It is necessary to check whether the positional relationship between holes, bolt diameter, and surrounding shape also work.

5. Is weight, transportation, and storage considered?

Dummy wheels are used as a set for all four wheels. In addition to the weight of a single product, the total weight including all four and accessories must also be confirmed.

Especially at a circuit, loading and unloading from the vehicle, moving to the pit, and repeated attachment and detachment during work occur. Heavy products can take a long time to set up and remove, and can also increase the workload on mechanics.

Points to check

• Weight per product
• Total weight including all four and accessories
• Can one person safely carry it?
• Can accessories be managed together?
• Is a transport/storage case provided?
• Do products avoid contact with each other inside the case?

Cases serve to consolidate products and accessories, prevent contact and loss during transport, and facilitate management at circuits and garages.

The 813 Alignment Tools dummy wheel kit stores the main unit and accessories in a large toolbox with an interior. This configuration allows management as a single unit from transportation to deployment on-site and post-use storage.

6. Does it avoid impeding vehicle movement during adjustment?

When camber or toe is changed, the contact point between the dummy wheel and the ground also moves.

If the contact point remains fixed to the ground, resistance may be generated in the suspension's movement, and force may remain in the suspension.

As a method to reduce this resistance, some structures use bearings or rollers at the contact point to allow for movement during adjustment.

Points to check

• Can the contact part accommodate front-to-back and side-to-side movement?
• Does it move smoothly with the vehicle loaded?
• Is it easy to settle the suspension after adjustment?
• Can it be used stably on a surface plate?
• Can the contact part be cleaned or replaced?

In alignment adjustment, not only the level of the measurement surface but also not hindering the vehicle's movement during adjustment is important.

7. Are replacement parts standardized and managed?

Dummy wheels are equipment that is used repeatedly over a long period. Over time, the contact points and accessories may need to be replaced.

When ordering replacement parts, it is crucial that parts can be managed by part number, rather than just by appearance or dimensions.

If part numbers are clearly stated in the instruction manual or parts list, ordering replacement parts will be smoother. Moreover, the fact that component parts are managed by part number is an indicator that the parts are standardized and continuously managed as products.

Points to check

• Are interchangeable parts clearly defined?
• Are part numbers listed in the instruction manual or parts list?
• Can replacement parts be ordered by specifying the part number?
• Can consumables be obtained individually?
• Is the replacement method explained?
• Can specifications changes or additional parts be discussed?

It is important to check not only that you can "consult if it breaks," but also that there is a system in place to identify and replace necessary parts.

Evaluate 7 items according to your needs

When choosing a dummy wheel, price and appearance are not the only things to consider.

1. Are the measurement standards clear?
2. Are the static shape and deformation under load considered?
3. Is the hub center height suitable for the application?
4. Can it be properly secured to the vehicle?
5. Is weight, transportation, and storage considered?
6. Does it avoid impeding vehicle movement during adjustment?
7. Are replacement parts standardized and managed?

Not all specifications are suitable for all users. It is necessary to organize the vehicle to be used, the measurement location, the frequency of adjustments, and the required work content, and select a product that meets each of these conditions.