I rented a car this weekend. The tire pressure indicator came on. At my
next stop I checked the tires and it turned out to be that the left front
tire was low. I filled it up and decided to check the spare to make sure it
was full of air just in case I needed it. When I opened the trunk, I
initially thought that the spare was a full size spare, because it sure
wasn't a donut.

After closer inspection I noticed that the tires on the car were
Bridgestones, 205/55-16, while the spare was a Pirelli 195/65-15. Under the
numbers it had the words "Standard load" OK, so it's not quite a full size
spare when compared to the tires on the car, but at least it's a real tire.
Then I noticed that the rim had the familiar "donut labels" on it. Limited
Use, Do Not Exceed 50 MPH, etc.

So what's the deal? Why would a full size tire, even if it was slightly
smaller than the original tires, have the Limited Use, reduced speed labels
on it? Granted, the smaller tire might make the handling a little weird.
Could that be the reason they label the spare as "limited use", etc?