No, no, no. It's a math thing. The percentage increase does not equal EXACTLY the percentage decrease, although the two numbers are very close to each other when the percentages are low.

Let's use some numbers where the percentage difference is bigger. Let's say one tire is 10 percent larger than stock. That means that when the speedometer and odometer think the car is going 100 miles, the car is actually going 110 miles. The odometer and odometer are going to read 9.1 percent (NOT 10 percent!) less than actual, because 100 miles is 9.1 percent less than 110 miles.

For the same mathematical reason, when the tire is 2.67 percent bigger, the speedometer and odometer read 2.60 percent less than actual.