Adjusting your speedometer might be the least sexy form of car maintenance imaginable, but it's absolutely necessary if you don't want a speeding ticket when you swear you were only going three over. Jason Fenske, host of Engineering Explained, spelled out all the steps necessary to make the adjustments as he tweaked the speedo on his Honda S2000. A speedo adjustment could be necessary when you change the gearing of the car, like Jason did, or even when you just change the tire or wheel size.
The end result is a much more reliable speedometer. In addition to being able to set new personal high scores, making sure your speedo isn't reading too low will save you a massive headache when you pass by those speed checkpoints going just fast enough.
Related: Here's how you can get a ticket for going the speed limit