What everyone is saying, but hasn't been explicitly stated yet, is that things are off by a percentage.
This applies to speed and distance, and the speedo and the odometer (and the diameter and the radius and the circumference and the rotations per mile and...)
If your new tires are 5% larger (circ, dia, whatever) than your old tires, all of the above is also 5% larger.
Also, it's all additive.
Tires are 5% bigger and speedo was 2% slow with stock tires, together you're now 3% faster than what the speedo is showing, and driving 3% more distance than what odometer is showing.
If speedo says 60, you're actually going 61.8 (60 + 3%).
Speedo says 85, you're actually going 87.5 (85 + 3%)
Odometer says you've driven 100 miles; you've actually driven 103.
I know someone else said ratio, which is the same thing, but thinking of it in terms of percentage is simpler.
This applies to speed and distance, and the speedo and the odometer (and the diameter and the radius and the circumference and the rotations per mile and...)
If your new tires are 5% larger (circ, dia, whatever) than your old tires, all of the above is also 5% larger.
Also, it's all additive.
Tires are 5% bigger and speedo was 2% slow with stock tires, together you're now 3% faster than what the speedo is showing, and driving 3% more distance than what odometer is showing.
If speedo says 60, you're actually going 61.8 (60 + 3%).
Speedo says 85, you're actually going 87.5 (85 + 3%)
Odometer says you've driven 100 miles; you've actually driven 103.
I know someone else said ratio, which is the same thing, but thinking of it in terms of percentage is simpler.
