For those of you with sports cars, or those of you who just like to work on your cars, and are planning on getting bigger tires than the ones you already have on or already to have them installed a speedometer calibration can be very important. When you are planning on getting bigger tires the distance around the tire is larger. Therefore, with each revolution, you are traveling further than before, or lower if you are having a smaller tire installed. Not only that but it also puts extra strain on your transmission so your vehicle will change its gearing ratio to adapt to that tire size, and if you don’t do that you can potentially damage your transmission. The speedometer in your vehicle reads how many revolutions the tires are making, but it doesn’t read how fast they are spinning.
Some people may ask, “why would I recalibrate my vehicle if I know roughly how fast I am going at different speeds?” Someone else may not know driving your vehicle, so it is nice to know that the speedometer is accurate, the odometer will also be accurate, otherwise, you really don’t know the exact miles for your vehicle. Knowing how fast your vehicle is going will help keep you from receiving a speeding ticket and keep everyone on the road safe. Furthermore, it can sometimes be used as a legal defense in court as well, as a defense against reckless driving.
Going to a local shop that offers speedometer calibration service as Safety Restore can be a great way to see what your speedometer is actually reading. The professional technician would start by connecting your car on a dynamometer which is a tool that measures the power output of an engine. Then they would run your car at various speeds to compare the known speed of the dynamometer, which is the speed is actually going, versus the speed, the speedometer is reading. After they have finished running your car they will show you the speedometer calibration chart with the comparison of those numbers at various levels of speed.