Overall wheel width and wheel diameter in relation to fitment is very important. Improper fitment can cause substantial issues, like rubbing of the wheel / tire combination on other parts of the vehicle. This can cause damage to both the vehicle as well as to the wheel/tire combination.
For example: If a tire that is too large for the vehicle and wheel specifications is installed, it could rub the sidewall on steering components or the frame itself. This will eventually weaken the sidewall to the point where it cannot hold air, drastically increasing chances of an extremely dangerous blowout.
We always suggest that if you are unsure what dimensions would be best suited to your vehicle to reach out to your local dealer. They would be able to take measurements if needed and advise you accordingly.