Wheel Tech in Simple Terms
Tyres Direct Wheel Size Guide
If you’re new to purchasing wheels you’ve probably heard the words ‘PCD’ and ‘Center Bore’ being thrown around, but are maybe unsure as to what exactly they are and what they mean for your vehicle. Well, we here at Tyres Direct have put together this handy wheel size guide section, where we take terms such as ‘Offset’ and explain them so that someone who’s never bought wheels before can walk away knowing what they’re talking about. So take a look below at the terms and their definitions. If you have any questions feel free to contact us and ask about our wheel range.
A Working Example
A good way to explain the terms used is to take an example and break it down. So, for example, one of our more popular wheels is our GOJOS 16×7 ET00 CB125 5×165.1 Modular in Black. So let’s take a look at what all these numbers and letters mean:
16×7 (Rim Size x Width)
This is the wheel’s height by it’s width in inches. So, in this example, the wheel is 16 inches high and 7 inches wide. In most cases only tyres with a 16 inch diameter will fit this wheel (how do tell the tyre’s diameter?).
This is the distance between the hub mounting surface to the centerline of the wheel. The ‘ET‘ stands for ‘EinpressTiefe’, a German word which translates to ‘insertion depth’ whilst the number is the distance in millimeters. If the offset is ET00 then is means the centerline of the wheel is even with the hub mounting surface. If the offset is a positive number (e.g. ET10), the hub mounting surface is on the front-half of the wheel (generally found on front-wheel drive vehicles), however, if it is a negative number (e.g. ET-10), this means the hub mounting surface is on the back-half of the wheel.
It is essential that you check your vehicle’s offset before purchasing wheels. Choosing the wrong offset can affect the handling and stability, making it potentially unsafe to drive. We recommned you check the vehicle’s handbook or consult with the manufacturer before looking for wheels.
CB125 (Centre Bore)
This is the centre bore of the wheel. The ‘CB‘ simply stands for Centre Bore whilst the number is the size in millimeters. The centre bore is the hole in the middle of wheel which helps centre the wheel properly on the vehicle. When the wheel is correctly fitted, having the correct centre bore for your vehicle can help reduce vibration when driving. Whilst some wheels are designed for specific vehicles, others are made to fit multiple different vehicles.
The PCD (Pitch Circle Diameter) also known as the BCD (Bolt Circle Diameter) shows what bolt fitment the wheel fits onto, notating the holes located around the center hole. In this example there are 5 holes around the centre, each of them 165.1 millimeters away from the hole on the opposite side (the diameter).