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Discussion Starter · #1 · (Edited)
What does PCD mean?

PCD stands for (pitch circle diameter) and is the diameter of a circle drawn through the centre of your wheel's bolt holes. PCD is measured in millimetres and also indicates the number of studs or bolts the wheel will have.

The most common fitment has 4 studs and a PCD of 100mm, hence the fitment 4x100.

What does OFFSET mean?

Your car requires a unique offset. Simply this is where the outside of the wheel needs to be in relation to the bodyline of the vehicle, realistically you can go 5-7mm outside these recommendations.

^ Click for larger image ^

The lower the offset number e.g. et49, et42, et40, etc.
The more the wheels will stick out from your car I think - et# is measured in mm.

The perfect offset for a corsa is et49 although this can cause problems with catching on the front brakes with some alloy wheel designs with most aftermarket alloy wheels. The best offsets for a Corsa C are et45 or et42. You can still comfortably fit et 49 and et40 too. Depending on wheels shape/style you may be forced into using et40, especially on an SRi with bigger brakes.

It is recommend to be between et40-45 on 17" alloys (17x7 wheel / 205/40/17 tyres). Arch modification shouldn't be required if you stick to these offset and don't lower you corsa too much. You should be fine with going as low as -30/-40mm with not too many problems.

Lower offsets like et38, et37 are possible but if you are lowering, expect problems with rubbing on your archs.
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