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Summary
  • A speedometer calibration test is a procedure that’s meant to assess the accuracy of your ride’s speedometer.
  • An inaccurate speedometer may need to be recalibrated or replaced.
  • Some factors that can affect speedometer readings include speedometer deterioration and collision-related damage.
  • You may also need to recalibrate your speedometer if you buy larger aftermarket tires.

A speedometer measures the speed of your vehicle. It provides real-time feedback to the driver through the vehicle’s dashboard, allowing them to maintain legal speed while traveling. Also, data regarding vehicle speed is also important to the vehicle’s on board computers.

Your vehicle’s speedometer needs to be calibrated properly to give accurate data output.

What Is a Speedometer Calibration Test?

A speedometer calibration test is a procedure that’s meant to assess the accuracy of your ride’s speedometer. The test is performed by using a dynamometer to measure your vehicle’s actual speed. The results will then be compared to the speed displayed on your dashboard.

It’s important to note that most repair shops can’t perform this procedure. That’s because you’ll need specialized equipment and computers to do this. Make sure to consult a professional before doing a speedometer calibration test.

It’s important to note that most repair shops can’t perform this procedure. That’s because you’ll need specialized equipment and computers to do this.

Anthony Harlin, ASE Certified Master Automobile Technician

What Is a Speedometer Calibration Report?

A report will be printed out once the speed calibration testing is done. This report will state if your ride’s speedometer is off. It will contain details about the discrepancy between the speedometer speed and the actual speed of your vehicle.

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Recalibrating Your Speedometer

If your speedometer is deemed inaccurate, you’ll need to have it recalibrated. A mechanic will usually adjust gear ratios and look into your vehicle’s tire size. Certain electrical components may also need to be adjusted so that the speedometer reading will be aligned with your ride’s actual speed.

There are plenty of videos online on how to calibrate a speedometer. However, if you’re not a seasoned DIYer, it’s best to let a trusted mechanic do it for you.

Factors That Can Affect Speedometer Readings

Many factors can affect your speedometer’s accuracy. Let’s discuss each one in detail:

Speedometer Deterioration

Like any other device installed on your vehicle, your speedometer may become faulty over time. For example, the sensors inside a mechanical speedometer can malfunction, causing inaccurate speedometer readings. Faulty connections within the system can also lead to erroneous readings.

In order vehicles, a cable is used to link the transmission to the instrument cluster. This cable can also wear out as the vehicle gains mileage.

Road Accidents

An accident or a collision can affect your vehicle’s health in so many ways. If you crashed your car recently, make sure to get your vehicle sensors and electrical components checked. Even if it was just a minor collision, it can cause one or more critical sensors to malfunction.

Aftermarket Rims and Tires

Is your speedometer off after installing new tires? This is perfectly normal. You’ll need to have your speedometer recalibrated.

Speedometers are calibrated according to the size of your stock wheels. So if you switch to larger tires, you’ll need to make some adjustments. The speed of your wheels can vary depending on the size of your tires.

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In some modern vehicles, you can make adjustments in the computer settings using a bi directional scan tool.

Worn Tires

Worn tires can also affect your speedometer reading. That’s because low tire pressure alters how your wheels rotate. Regularly check your tire pressure to avoid speedometer inaccuracies and prevent accidents on the road.

Why Is It Important to Get Accurate Speedometer Readings?

speedometer calibration
Aside from getting a traffic ticket and paying fines, you’re also risking your safety by not fixing an inaccurate speedometer.

As a driver, you need to know your ride’s actual speed because it can help you adhere to speed limits. Speeding, although unintentional, can still earn you a traffic ticket.

Aside from getting a traffic ticket and paying fines, you’re also risking your safety by not fixing an inaccurate speedometer. Exceeding safe driving speeds can lead to accidents while on the road.

Speedometer Readings as Evidence In Court

Another reason why accurate speedometer readings are important is the fact that they may be used as evidence in court—especially if you’ve been charged with reckless driving. In some cases, inaccurate speedometer readings can be used as a mitigating factor in determining whether a driver is guilty or not.

However, the results of a speedometer calibration test can still be questioned by experts. The judge will also consider supplementary evidence like witness testimonies and video recordings.

What’s the Difference Between an Odometer and a Speedometer?

Although these two devices are related to each other, they function differently. A speedometer measures the actual speed of your vehicle. Meanwhile, an odometer measures the overall distance traveled by a vehicle. It’s also important to note that changing an odometer reading is against the law.

How Much Will a Speedometer Calibration Cost?

Expect to spend around $50 to $100 for a speedometer calibration.  The actual price will depend on factors like the make and model of your vehicle and the labor costs in your area.

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How Much Does a Speedometer Replacement Cost?

If it’s not an external issue, and your actual speedometer is faulty, you’ll have to get a speedometer replacement.

In most modern vehicles, the speedometer is integrated into the instrument cluster. It’s repaired by a specialized shop that works on instrument clusters. It can also be replaced as an assembly.

Expect to shell out anywhere between $50 and $200 for the speedometer. Some speedometers can be priced higher depending on the brand you choose and the make and model of your vehicle. Mechanics usually charge anywhere between $50 and $100 for this type of replacement.

Remember that these prices are just estimates. You’ll have to consider taxes and other charges as well.

Is It Okay to Use My Phone as a  Speedometer Substitute?

There are several mobile apps designed to work as a portable speedometer. Some of these apps can work offline, so you don’t have to be connected to wifi all the time.

However, nothing can replace your actual vehicle speedometer. Your phone can die anytime, and it may leave you clueless about your actual speed while traveling.

Instead of using your phone, it’s more reliable to use a plug-in device that connects to your OBD2 port, capable of displaying various computer parameters on the screen. This solution is particularly useful if your conventional speedometer is not functioning correctly.

You can use your phone as a temporary substitute in emergencies. However, you’ll still have to recalibrate or fix your speedometer to stay safe while on the road.

About The Authors
Written By Automotive and Tech Writers

The CarParts.com Research Team is composed of experienced automotive and tech writers working with (ASE)-certified automobile technicians and automotive journalists to bring up-to-date, helpful information to car owners in the US. Guided by CarParts.com's thorough editorial process, our team strives to produce guides and resources DIYers and casual car owners can trust.

Reviewed By Technical Reviewer at CarParts.com

Tony Harlin is a Master Gas and Diesel Diagnostic Technician with over 18 years of experience. He works full-time at a large independent automotive shop as a driveability and repair technician working on all types of vehicles with a focus on diesels. ASE certifications include A1-A9, L1 and L2, as well as X1.

Any information provided on this Website is for informational purposes only and is not intended to replace consultation with a professional mechanic. The accuracy and timeliness of the information may change from the time of publication.

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