There are essentially two types of rims; steel rims and light metal rims, which are also called alloy rims. The steel rim is the most common and is mounted as standard on most vehicles, but the alloy rims have recently become more common.
The rim's size is printed 8.5x18. The 8.5 indicates the width of the rim in inches, and 18 is the rim's diameter. The rim size is also determined by the bolt circle, hub bore and wheel offset. These various components can be found in several different combinations.
The bolt circle on a rim
The bolt circle is the diameter of the circle in which the rim bolt holes are found. The bolt circle thus indicates how many bolt holes the wheel has and what the distance is between the bolt holes. The diameter of the bolt circle is measured in mm, together with the number of bolt holes. It can be given as 5/100, when the wheel has five bolt holes with a 100 mm circular diameter.
With an even number of bolt holes, you should measure the circular diameter from the inner edge of one bolt hole to the outer edge of the opposite bolt hole. In the case of a rim with five bolts, you can measure as shown below.
- A. Measure the entire bolt hole diameter
- B. Measure from the edge of the bolt hole to the edge of the hub bore
- Multiply B (the measurement result) by 2
- C. Measure the diameter of the hub bore
- Bolt circle diameter: A+Bx2+C
You also can use our Wheel search option to find the right rims for your car!
Hub bore on a rim
The hub bore, also called the centre line, is the hole in the centre of each rim which should fit to the hub of the car. Some rims are drilled to fit directly to the hub dimensions, but for others a centring ring is used. It is important that the hub bore centres correctly to prevent vibration from occurring.
The wheel offset is called ET measure or simply offset. This measures how much the rim is in or out of its centreline, i.e. the distance between the hub mounting surface and the centreline. A rim that has an offset/ET of 45 sits 45 mm off the rim's centre line. The more offset the rim, the farther out the wheel protrudes. A rim that has an offset of 25 protrudes therefore farther out than a rim with an offset of 45 It is important to have the correct offset for your rim. Too small an offset may cause the wheel to rub against the inside of the car's fenders and too high allows the rim to scrape inside the car's wheel arch. A change of ET can cause the car's driving performance to change significantly.
Dismounted rims – AVM
A dismounted rim is a rim that has been used in the factory for the production of cars. So while a car is being built, it rides on these rims. The rims are dismounted later and are then sold. The rims have never been driven in traffic.
Rim care and maintenance
Since the wheels (as well as the tyres) are exposed to road dirt, salt, and brake dust that contains particles that attack the rim's surface, it is important to keep them clean to extend the life of your rims. Moreover, rims that are well-maintained and cared for look much nicer.
You should clean alloy rims with water and mild car shampoo. If you use stronger detergents or certain types of rim cleaners you can damage the rim. Use a soft sponge and make sure that the rim is cool when you start cleaning. The best way to care for your rims is to start by rinsing the worst dirt off with plain water, before using a sponge and shampoo. This way you will not be polishing a rim still containing dirt or sand. There are various resources available on the market that has been developed for cleaning rims and maintaining their appearance. These may contain strong acids which ultimately can damage your rims. This is why we recommend a mild car shampoo to ensure a longer, shinier life for your wheels.