Cadillac 2012 CTS Owner's Manual page 415

Driving with more than one
compact spare tire at a time could
result in loss of braking and
handling. This could lead to a
crash and you or others could be
injured. Use only one compact
spare tire at a time.
If your vehicle is equipped with a
compact spare tire it was fully
inflated when the vehicle was new, it
can lose air after a time. Check the
inflation pressure regularly. It should
be 420 kPa (60 psi).
After installing the compact spare
on the vehicle, stop as soon as
possible and make sure the spare
tire is correctly inflated. The
compact spare is made to perform
well at speeds up to 105 km/h
(65 mph) for distances up to
5 000 km (3,000 mi), so you can
finish your trip and have the full-size
tire repaired or replaced at your
convenience. Of course, it is best to
replace the spare with a full-size tire
as soon as possible. The spare tire
will last longer and be in good
shape in case it is needed again.
Do not use the compact spare on
other vehicles.
And do not mix the compact spare
tire or wheel with other wheels or
tires. They will not fit. Keep the
spare tire and its wheel together.