Tires: spare tire different width

Question
My car has P235 tires on them and I have no spare.  I have P245
tires that are in good shape.  Everything else on the number is the can I use the P245 tires as a spare

Answer
Betty,

There is more to tire size than width.  The current size format is this:

Width (in mm)/Aspect Ratio(a number ending in 5 or Zero) R (for Radial) rim diameter (in inches)

So I can't tell you if the 245 tires is a good option for a spare because there are combinations that would be terrible.

But as a general rule, the spare ought to either be what the vehicle manufacturer provides (as in minispare) or the same size and original.  Unfortunately, there are lots of variations.

So post back with the entire size, and the kind of vehicle and I'll respond.