There are different 15mm spacers: bolt-on ones and slip-on ones. The bolt-on spacers are bolted to the vehicle studs and following the wheels are secured on the spacers with provided lug nuts. They are perfect for vehicles that use lug nuts to lock the wheels. On the other hand, slip-on spacers simply slide over your existing wheel studs, secured by a set of new longer studs. In fact, they are primarily made for vehicles that use wheel bolts rather than lug nuts.
By measuring the wheel gap or well calculating the offset, you come to the conclusion that 15mm spacers are perfect. So, you have decided to use bolt-on 15mm spacers. There is more to consider when shopping for wheel spacers. Now let’s leave other considerations aside, and focus on the design and materials. These two factors actually are very important for wheel spacers safety.
15mm Spacers: Hub-centric or Lug-centric
The simple way to figure out hub-centric or lug-centric 15mm spacers is to check the hub diameters. Usually, a hub-centric wheel spacer is machined to fit the specific vehicle hub. For example, the 5×114.3 Lexus ES spacers are made to fit exactly to the 2022 Lexus ES that runs the 5×114.3 bolt pattern. The center bore is designed to be 60.1mm which is the diameter of the hub flange where the wheel seats to the hub. Most originally equipped wheels are hub-centric. Therefore, hub-centric 15mm spacers allow for a stable and firm connection. The wheels can be properly mounted and accurately balanced.
Conversely, lug-centric 15mm spacers are made with big diameters which allow them to fit a variety of vehicles. They are usually cheaper. However, they are not specific to the car, when installed, there will be a certain gap between the bolts or the wheels. This gap can cause vibrations in the ride. Lugs can be bent under force and provoke vibration if you keep the wheels unbalanced for a long time.
Active Cooling 15mm Spacers
BONOSS active cooling 15mm spacers are designed with heat dissipation grooves to make brake cooling better. Distributed in petal shape, these grooves allow the external cold air to flow continuously inside the wheel spacer when it rotates. The air takes away the heat, so it achieves the purpose of actively dissipating heat for the braking system. There are small notches that are distributed on the corner of wheel spacers. These notches act as air collectors which tremendously enlarges the airflow, enhancing the heat dissipation effect, and improving road safety.
When it comes to the brake system, apart from braking capacity, heat dissipation is another important aspect. In short, aluminum 15mm spacers have better thermal conductivity than steel ones. Besides, they are much lighter which improves handling and body control. aluminum 15mm spacers are much better in corrosion resistance. When aluminum is exposed to water it creates a film of aluminum oxide over the metal that protects the metal beneath it from corrosion. This means they are not easy to corrode or oxidate which makes them safely work for long-term use.