Important Specifications when Buying Rims

When buying your sport rims, your will need to know the specifications of your rims, for example, rim size, rim offset, centre bore size, bolt pattern and the bolt circle diameter, or better known as the pitch circle diameter (PCD) in the Singapore context. These specifications vary across different car makes and models and you should know these numbers before shopping for your set of wheels . If not, please find out from your local car dealer or the owner’s manual.


Rim Size

Choosing the rim size is easy. In Singapore, car owners usually keep their current rim size or choose to ‘plus size’ their rims. Plus size refers to upgrading the rims size, for example from the current 16 inch rims to 17 inch rims. When plus sizing, it is important that the rolling circumference remains the same. Else, your speedometer may not give you an accurate reading. Because of this, dealers often offer you rims and tyres package so that you get the right fitting tyres for your rims. While larger rims give your better handling, excessively large rims can increase your fuel consumption. This is due to the additional weight from your rims – metal weighs more than rubber given the same volume. Find out how to find the right tyre size that will fit your new rims.

Rim Offset

Rim offset is the distance between the centreline of the rim and the back face of the rim. Most rims have positive offset and the offset on your new rims should not be too far off from your current set of rims. You can read more about rims offset here.

Centre Bore

There is also the centre bore size, which is the diameter of the hole in the centre of the rim. Ideally, the centre bore should match perfectly to reduce vibration. However, most aftermarket wheels are produced with larger centre bore in order to cater to different hub size. The “hubcentric ring” will be installed in order for the larger centre bore rims to fit onto the smaller hubs. The important thing is that the rims you buy, new or used, must have equal or larger centre bore size.

home22Bolt Pattern and PCD

Bolt pattern is the combination of the number of lug holes in the rim and the PCD. The number of lug holes is obvious from counting the number of bolts on your existing rims. It is usually 4 or 5. Smaller cars may have 3 while bigger vehicles like pickup trucks and large SUVs may have up to 8.

Next, consider the PCD. If you draw an imaginary circle that passes through each of the bolts, the distance across the circle is the PCD. In Singapore, the number is expressed in inches (4.5”) or millimetres (100mm). When you put these two figures together, you get the bolt pattern (4 x 100mm or 5 x 4.5”).

When buying your sports rims, new or used, the bolt pattern should match exactly with your current configuration. For example, rims with bolt pattern 5 x 115mm must not be fitted on a car that requires rims of bolt pattern 5 x 4.5” (4.5” = 114.3mm). Installing rims with the wrong bolt pattern will affect the car’s performance and cause damage to your car.

You can get the correct bolt pattern and PCD from your local car dealer. Alternatively, you can use our guide to check the specifications of the bolt pattern, PCD and centre bore size of your car.

TIP: If you have changed your bolts for your new rims, make sure you have the right spanner that will fit your new bolts.