I know a lot of you have tuned your trucks with the Superchips program. I just ran it on mine last weekend. I used the speedo calibration option because I'm running 285's. It may be my imagination, but I swear I'm getting passed on the interstate by a lot more people than I used to and I'm going the same speed as usual (according to the speedo). On a side note at 75mph I'm hitting 1900rpms and that doesnt change much from 70-80mph (is that good/bad?).
In short, I wanted to know if anybody has had calibration issues the the chip, or if it's correct and I'm going crazy.

Thanks

 

You'll want to take a tape measure and actually measure the size of your rear tire under the normal load (not your big loads, but not jacked up either). Although mine reads 35, it actually measures at 33.75. That's the size I put in my SC and it reads almost spot on (I'm off by 1mph at 75 according to the gps).

 

Yeah the 285's are equivalent to about 32.83" so I entered 32.75
I just went outside and got a true measurement...31.75" under standard load.

Thanks for the help.