[mightytexn]

It is logging less miles....here's a theoretical example to explain it....suppose stock tire size it takes you 1 hour driving with the speedo at 60 miles an hour to get some place, then you are driving 60 miles....with the GSR rims on just say it takes 30 minutes driving with the speedo at 60 miles an hour to get to the same place (I know the real change isnt that much but its easier numbers to work with)....the car thinks you only went 30 miles because you drove half the time at "the same" speed.....both the speedo and odometer rely on having the proper outside diameter on your tires to be correct.