Your GPS is telling you that the tires are too small. Way too small.

You can (I do) run a 245/65x17, and the speedo will be much tighter on reality.

Your GPS is right to within a few feet on location, and it's only wrong because the original military applications that went to civilian use were required to have an error in both time and space.

If you get bigger tires, 245/65x17, then the tires turn slower for the same speed, or more speed comes from the same speedo reading.

Bottom line, the 225s are too small. Do not buy them again.