What are hub rings and wheel spacers? Custom method to pass the scrutineering and vehicle inspection | MOBY [モビー]

The hub ring and wheel spacer are indispensable items when setting the tsuraichi with an external wheel. In addition to explaining the roles and precautions of each hub ring and wheel spacer, we have picked up 9 recommended products including wide tread spacers. Make full use of the hub ring and wheel spacer to aim for safe wheel mounting.

Hub rings and wheel spacers are used for customizing wheels and tires

Wide tread spacer
© Владимир Разгуляев / stock.adobe.com

Both the hub ring and the wheel spacer are parts related to fixing the wheel, and are custom parts for mounting the wheel in a cool and safe manner. However, since the wheel hub is a part where a large force is applied during driving, improper installation may cause damage to the hub bolt or tire drop accident. When using hub rings and wheel spacers, it is important to correctly understand their roles and types, how to choose them, and whether or not to pass the vehicle inspection, and handle them safely.

Hub ring | Indispensable when replacing with an external wheel

The hub ring is a ring required to fill the gap between the center hub and the wheel when the wheel is installed outside the company. The center hub diameter is set to a different diameter for each automobile manufacturer, and the genuine wheel is designed to match the hub diameter exactly to suppress blurring during driving and reduce the burden on the hub bolt.

On the other hand, external wheels that are supposed to be installed in cars of various manufacturers have a large center hub hole, and the center of the wheel is slightly misaligned, which tends to cause blurring during driving. The hub ring is a part that fills the gap between the center hub and the external hole to correct the mounting position of the external wheel to the center of rotation, and secures the same wheel mounting strength as the genuine one even when the external wheel is installed.

Wheel spacers | Items that can make tires into a tsuraichi

A wheel spacer is a part that can shift the wheel mounting surface to the outside by sandwiching it between the hub surface and the wheel mounting surface. By being able to change the tread width, which is the distance between the left and right tires, it is useful for changing driving characteristics and making fine adjustments when making a tread setting with the tire surface and fender surface aligned.

The thickness of the wheel spacer is sold in units of several mm, and the mounting position of the wheel moves outward by the thickness of the sandwiched spacer. However, the amount of wheel locknut that is applied to the hub bolt is shortened by the amount that the spacer is sandwiched, and the risk of damage to the hub bolt or the wheel falling off increases. If you pinch a spacer of approximately 8 mm or more, you will need to replace it with a longer hub bolt or a wide tread spacer.

What is a wide tread spacer?

A wide tread spacer is a wheel spacer with a hub bolt used when expanding the tread by 10 mm or more. By fixing the wide tread spacer to the hub bolt on the vehicle side and fixing the wheel with the hub bolt embedded in the spacer, the wheel mounting position can be changed more greatly. At that time, if the normal hub bolt protrudes from the wide tread spacer, it is necessary to install a wheel with the hub bolt relief processed.

What impact does the wheel spacer have on driving and safety?

Affects handling and traction

The change in running performance due to the wheel spacer becomes more effective according to the amount of expansion of the tread. As the tread is expanded, the suspension feels softer and the amount of roll decreases, so it is possible to make a difference between the front and rear treads and fine-tune the driving characteristics and the ground contact of the tires.

Another advantage is that when the tread of the drive wheels is expanded, the difference in rotation between the inner and outer wheels becomes larger, and the LSD-equipped vehicle has a stronger differential mechanism. However, if the steering wheel is enlarged, there is a disadvantage that the steering wheel can be easily taken due to disturbances such as steps and ruts.

Excessive tread expansion may cause a tire drop accident

The more you use the spacers to widen the tread, the greater the strain on the spacers and hub bolts, increasing the risk of tire dropouts due to spacer breakage. If the wheel is hit hard, you should consider that the spacer cannot be reused. In addition, the burden on the spacer will increase depending on the condition of the vehicle and the driving environment, such as the weight and speed of the vehicle.

Along with this, in order to maintain a safe condition, it is essential to check for cracks, distortion, rust, corrosion, etc., and to perform regular maintenance such as bolt tightening torque management.

Can’t you attach the hub ring if you bite the wheel spacer?

Except for some wheel spacers, spacers and hub rings cannot be installed at the same time. If a wheel spacer is installed, the amount of protrusion of the hub will be reduced by the thickness of the spacer, so it may not be possible to secure a sufficient amount of meshing and the performance of the hub ring may not be exhibited. If you want to install the spacer and hub ring at the same time, the right choice is to use a wheel spacer with hub ring.

Wheel spacer with hub ring |

If you want to adjust the tread amount while firmly engaging the center hub and the wheel, use a wheel spacer with a hub ring. Spacers with hub rings include products made with hub diameters that are premised on the installation of external wheels and products that are premised on the installation of genuine wheels from each manufacturer, so be careful about the product dimensions when purchasing. If you attach a hub ring to the product for genuine wheels, you can firmly fix the wheels outside the company.


The advantage of using a wheel spacer with a hub ring is that it is safer because the wheel can be mounted more securely. Since the center hub and the wheel can be firmly engaged to adjust the tread amount, it is possible to reduce the burden on the hub bolt and put it in a tread state.


The disadvantages of using a wheel spacer with a hub ring are the high price and the time and effort required to select the product. It is necessary to select a product that matches the hub diameter, number of hub bolts, and bolt spacing dimensions of the vehicle to be installed, and it cannot be installed only if one of the dimensions is different. It is more expensive than a spacer without a hub ring because it is laborious to process.

Will the vehicle inspection pass if the hub ring and wheel spacer are installed?

With or without hub ring, it’s OK if the wheel is safely installed

There are no clear safety standards for hub rings and wheel spacers, so if the wheels are installed safely, they will pass the vehicle inspection with or without hub rings and spacers. However, too extreme wide treading is considered structurally dangerous and may be considered non-conforming depending on the location and inspector undergoing the vehicle inspection.

It is NG if it is a “protruding tire” due to the wheel spacer

By installing the wheel spacer, if the tire and wheel protrude from the fender, it will not meet the safety standards and will not pass the vehicle inspection. Due to the revision of safety standards on June 22, 2017, tire protrusions up to 10 mm are permitted, but the standards for wheels are the same as before. In order to pass the vehicle inspection, the range of 30 ° forward and 50 ° rear from the top of the wheel must be within the fender.

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