Wheel spacer shims
Wheel spacer shims are most commonly used to push wheels 3-7 mm because the inside of the rim is hitting the suspension components. These spacers do not need to be "hubcentric", because the original wheel hub lip of the car extends into the wheel through these spacers since the width is only 3-7 mm.
Purpose: The wheel hits the inner suspension assembly to improve the stance.
Things to note: Make sure the spacer PCD (bolt pattern) matches your car. Generally, they are universal and applicable to various PCDs. Does the kit include bolts? Bolts that are 5 mm longer than stock should be need. Make sure that the center bore of the shim is the same size or larger than the center bore of your vehicle.
Bolt/stud through spacers
The most common type of spacer is usually used to improve the stance/appearance of the vehicle.
Your wheel is attached to the hub by these spacers, and then you pass your extension bolts through the wheel, spacers, and into the hub.
Purpose: Improve stance
Please note: Hubcentric spacers should only be used if the spacer is wider than 7MM. In addition, the spacer will extend from the hub lip of your car into your rim, allowing your new hub lip to slide into the spacer. This is an absolutely crucial step. It is always recommended to use forged spacers. Anything less is not acceptable. Spacers cast in aluminum are not manufactured to the same tolerances as forged ones. They may cause vibration if they are not manufactured correctly.
Bolted spacers with studs
Bolt spacers are used in cars where bolts protrude from the hub instead of bolts inserted.
Bolt spacers also allow you to change the PCD of the vehicle.
Use case: Abel has a 1995 Nissan S13. The wheels are 25 mm above the arch. For aesthetic reasons, Abel wants them to be consistent with the arch. He bolts the spacers to his car using the supplied nuts with the spacers. The spacers are now bolted to the car and will stay there even if the wheel is removed. New studs protrude from the spacers. Abel installs the wheel in the same way as without the spacer, using the studs protruding from the new wheel spacers and using his standard wheel nuts.
Check that your spacer's inner and outer center bores match your wheels and your car. To maintain compatibility with your standard wheel nut, make sure the stud on the spacer matches your original stud.
Bolted spacers with bolts
When using a spacer with a width of more than 30MM, bolt spacers with bolts are usually used.
Bolt shims can also be used to replace wheels easier without having to reinstall the shims every time the wheel is removed.
Bolt gaskets are also used to change the PCD of the vehicle.
Use case 1: Jack has a 2015 BMW 5 series. Jack's BMW is 5x120 PCD. The only wheel Jack wants to buy is 5x112. Jack bolted the bolts to his BMW (5x120), then bolted the wheels to the spacers (5x112)
Use case 2: Bill wants to install 50mm spacers on his BMW M3. The fenders of BMW are wider than the factory fenders and require the wheels to be aligned with the fenders. Bill uses his BMW on the track and constantly changes tire and wheel combinations. He uses bolt spacers instead of bolts to penetrate the spacers because he wants the spacers to stay in place when changing wheels to increase speed.
It is important to ensure that the spacers' inner bores match your car, and the outer ones match your wheels. To ensure that you can use your original wheel bolts, make sure the threads of the bolt holes on the spacers match the threads of your car.
