Will these tires fit?

I have a 1999 Ford Taurus that has 205/65R15 tires on them. I'm looking to replace them and a friend of mine has a set of 205/70R15. Will those tires fit on my Taurus

Yes they will fit
The car will ride 10mm higher and the gearing will be slightly higher.
The speedometer will read slightly slower too.

Sounds very promising.

As long as they have the same amount of holes on the tire and the rim isn't like 4 inches bigger your fine. The main factor is the holes

You should never go over or under 3% of the OEM size. The 205/70R15 will be 3.17% larger in overall diameter. Your speedometer will read 2 mph slow. You are borderline with these tires and you will have less tread width on the road for stopping. I would not advice you to use these tires but you probably can with no harmful results. Your choice.

They will fit, though the circumference is slightly different which will have a small effect on the gearing and the speedo.

Cool