None that I have found. Recalibrated for 285/75 17s, shift points changed fine, MPG's, etc. I would buy another without hesitation.
Measure what they actually measure mounted and then input that into the Jscan, that should get it pretty close.I know this is old but I put on 285/75/17 NITTO ridge grapplers tires on and just ordered the jscan because my speedo is +2 to 5 and I think the shift points are off. My mpg is 16 on highway.
What tires measurement did you use for your calibration? I've read that just putting in the actual measurement isn't the way it goes that it will be a little less.