Understanding Wheel Sizing and Stud Patterns
Need support in understanding wheel sizing and bolt patterns? Here you can learn to measure PCD, wheel diameter, centre bore and offset with this easy guide for buying spare or replacement wheels.
If you’re replacing a wheel or buying a spare for your vehicle, its easy to get lost in technical jargon – PCD, offset, centre bore… what does it all mean?
Other you’re dealing with a cracked alloy, a bent rim, or simply want a backup in case of a flat tyre, understanding your wheels size and fitment is essential. This guide breaks it all down in simple terms so can you shop with confidence.
What Size Wheels Fit My Car?
When looking for a spare wheel, if you simply search your make and model of your vehicle, you will be shown all the compatible wheels and tyres that are suitable for your vehicle. We will now guide you in becoming competent in recognising the size of your wheel if you wanted to check it out for yourself.
- Wheel Stud Pattern (PCD)
Also known as the bolt pattern, this tells you how many holes are in the wheel and how far apart they are. PCD stands for Pitch Circle Diameter.
Common Examples:
- 4 x 100 = 4 holes, 100mm apart
- 5 x 114.3 = 5 holes, 114.3mm apart
To measure your PCD:
- Count the number of bolt holes
- Measure the distance between them
- Alternatively, check the back of the wheel for any stickers for a PCD markings
2. Wheel Diameter
This is the total diameter of the wheel, usually measured in inches. You can find it print on the tyre sidewall. For example, if your tyre reads 225/45/R17, that means it is an 17 inch wheel. No tyre fitted? Measure across the full width of the wheel from one edge of the rim to the opposite edge.
3. Wheel Width
This is how wide the wheel is from one side of the barrel to the other. It’s usually marked inside the wheel, but if not, use a tape measure from the front to back of the wheel.
4. Centre Bore
The centre bore is the hole in the middle of the wheel that fits over the hub of the car. it helps centre the wheel and reduce vibration. If the centre bore is too small, the wheel won’t fit. if its too large, you may feel vibrations unless spigot rings are used.
To measure the centre bore:
- Look at the inner diameter of the hole on the back of the wheel
- Or measure the hub lip on your car
5. Wheel Offset (ET Number)
Offset determines how far the wheel sits in or out from the wheel arch.
- ET numbers are marked on the back of the wheel (e.g ET35, ET45)
- A lower ET number means the wheel sticks out more
- A higher ET number means it sits further inside the arch
Need Help Choosing the Right Fit?
Don’t stress about measuring, at Spare Wheels For You, we do the hard work for you. Just use our easy vehicle search tool and we’ll match your car with compatible spare wheels in seconds. Alternatively, get in touch with our expert team who are here to help.
