I am looking to buy a low budget alloy rim to use as a full size spare but am really struggling to understand the options that are suitable. Most alloy wheel sites suggest different sizes, but when I specify 7.5 x 18 the most common seems to be 7,50x18 5x114.30 ET50.00 for my car but the size parameters on the standard 18" alloys on the Mazda website are 7,5J x 18, Offset 60 mm, OE-design 140.
How critical is it that the rim matches exactly for ease of fitting (think dark wet country lane!) and for safety (think motorway!)?
Can anyone help please?