Operation Spare Tire

Be aware that tires age even if they aren't used and it's recommended that you replace them 10 years after the date of manufacture. So if the tire dates from 2005 (or even possibly a year earlier, you can check the date of manufacture from the 4 digit code on the tire, the first 2 digits are the week and the last 2 digits are the year) then I'd certainly recommend you replace it.

 

I currently have a 2021 Prius PHV (aka Prime in the US). At the time I bought a second hand space saver wheel on ebay which was fitted with the 125/70D17 tyre/tire which is the recommended space saver size by Toyota , however it was made in 2006 so I decided to replace the tire. Interestingly if you use the tire size calculator for the standard full size 195/65R15 that gives a diameter of 25"(635mm) and a circumference of 78.4"(1991mm), whereas the 125/70D17 gives a diameter of 23.9"(607mm) and a circumference of 75"(1905mm), which is quite significantly smaller. So I replaced the old 125/70D17 space saver tire with a new 125/80D17 one which is a much closer match to the full size dimensions with a diameter of 24.9"(632mm) and a circumference of 78.1"(1984mm). It's just a bit puzzling why Toyota chose to use 125/70D17 rather than 125/80D17 which gives a better match.

 

3rd Gen has the same stock tire, but a different temp spare size. It’s quite close in diameter. Not sure why Toyota would change the spec, but more’n likely $’s.