Sorry, more like 5%.
Somebody jump in here and correct me if I'm wrong.
It says that when my speedo reads 60mph, I'm actually going 63.
Wouldn't that mean if I go 60 miles(according to speedo), I am traveling 63 miles?
Shouldn't I show better than actual mileage?

http://www.miata.net/garage/tirecalc.html

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'85 300SD (formerly california emissions)
'08 Chevy Tahoe
'93 Ducati 900 SS
'79 Kawasaki KZ 650
'86 Kawasaki KX 250
'88 Kawasaki KDX200
'71 Hodaka Ace 100
'72 Triumph T100R