This talk of a spare brings back memories of a trip to the tire store a long time ago....I come from the 2 tire world, every time I or anyone I knew, father, brother, sister, or friend need new tires they always got 2 new ones. You took the old tires off the front, put them on the back and the 2 new tires went on the front, that was how it was done.
This trip I guess the tire sales guy was having a slow day and wanted to mess with someone, I ask for my usual 2 tires and the guy said ok but you know you can get 4 new tires don't you. I said "No, no way man, are you crazy, stop messing with me." He said "Hey is ok I'm not kidding you really can get 4 new tires.
I needed more info "How can you do it, I've never seen anyone get anything but 2 tires?" He said "This is how we do it, we sell you 2 tires on the invoice and 2 more tires on a invoice a few numbers down from your first invoice. Then when the guys install then they do the fronts like usual but then go work on another car for awhile and then come back later to put 2 new tires on the back instead of the used fronts, most 2 tire world guys don't pay much attention to what we are doing and miss it." It was a little mind blowing to have your world view blown up, but after thinking about it and for once having enough money to cover it I said ok.
Now it really must have been a slow day, as I was waiting for the install to complete the guy said "Hey man, do you really want another mind blower, you can get 5 new tires. This was too much "How is that possible a car only has 4 wheels?" The guy said "That's true the 5th tire is your spare!!!!"
"No man you can't be serious, a spare is a old crappy tire most likely low on air if not flat, how can anyone in their right mind put a brand new tire in the trunk, how is that possible?"