245s to 265s

I just upgraded from my stock 245s to 265s. The 245s not only looked too small, but they also were causing my speedo to be off by 3 - 5 mph. Since they were smaller, my speedo would read fast campared to my gps. With the 265s, the speedo and gps are dead on. Does Toyota calibrate all the Tacomas as if they had 265s regardless of what tire is on there? Also, since my speedo was reading fast, wouldn't it make sense that my odometer has also been turning too fast? In other words, I have more miles on my truck than I've actually driven...