I have a 2019 Ram 1500 5.7. I installed larger tires going from 275/55/20 Falken to Michelin 275/65/20 Ltx AT/2 E load. I had a speedometer difference of about 4 mph. After reading many reviews & forums I ordered the Hypertech 3400 from Amazon. It seems some folks had issues in the past with larger tire size calibration messing up the park assist or park sensors. I believe that those instances usually involved larger tires than what I installed. It didn't affect my park sensors or anything else. The Hypertech 3400 was straight forward and simple. I updated it on my laptop to ensure it had the most up-to-date info, and once hooked up to my truck, it took 10 min. or less to program. Using 33.50 as the tire size, my speedometer is spot on now, with no issues whatsoever.