Offset, width and diameter of a wheel
How critical are a wheel’s offset, width and diameter?
I recommend reading the article that sets out more on the operating parameters of wheels, but in short you can put it like this: whatever sellers tell you, a wheel’s width and diameter must strictly match one of the tyre sizes specified by the car manufacturer (you will find the full list of them on the inside of the fuel filler flap, on a sticker inside the driver’s door opening, or in the car’s owner’s handbook: as a rule this is a table of tyre pressures for each of the specified sizes). And the offset must exactly match the manufacturer’s requirements: a given car model has one offset, and it is not a range of acceptable values but a specific figure.
Yes, wide wheels with a large radius are more expensive and look better, so it is convenient and profitable for sellers to convince buyers that the overall wheel diameter is the main parameter, but in doing so they say nothing about the fact that the suspension of any car is designed around specific loads and forces, and how those loads are distributed is different for tyres of different profile heights and widths. On top of that, a low-profile tyre will pass far more force on to the suspension with any impact or pothole, which will substantially shorten the suspension’s service life, and driving the car on an imperfect road surface will become many times less comfortable.
Wheel offset is a separate story. Some sellers simply “pay no attention” to this parameter at all (saying the wheel fits as long as it seats properly on the hub), while others try to convince motorists that +/- 5 is an acceptable deviation. All because there is a huge number of possible offsets (even within a single car maker, the design offset can differ from model to model), there is no single standard, so it is far from certain that every wheel manufacturer’s range has a product that exactly fits your car. They simply want to sell you wheels at any price, and nobody is worried about your safety!
In fact, a wheel’s offset determines how lateral loads are distributed across the key components of the suspension, and is therefore a decisive factor in making sure the suspension works correctly (as intended by the car manufacturer) in every situation. And wheel offset that does not match the car manufacturer’s requirements can lead to extremely sorry consequences, and this is about far more than just the service life of the ball joints or the track rod ends.
Whatever a wheel manufacturer writes in its advertising, and whatever a seller in a shop tells you, the fact that a wheel seats properly on the hub and does not foul the callipers or the track rod ends does not mean this wheel is right for you: without exception, every parameter must strictly match the car manufacturer’s requirements. Remember that an electrical fault on the road, or even an engine failure, will most likely just cause you financial trouble, while any problem with the suspension can create a direct threat to the life of the driver and passengers. So neither looks, nor aesthetics, nor fashion can justify breaking the car manufacturer’s requirements for wheel size.