A vehicle transfers power from the engine through the transmission and differential. The gears in these components result in a wheel speed expressed in revolutions per minute rpm. From the wheel speed rpm, the size of the tire determines the final road speed of the vehicle. The calculations can be applied to any vehicle, from a bicycle to a semi-truck. Calculate the circumference of the wheel in feet from the diameter.

The formula for circumference is the diameter times pi. Pi is a mathematical constant and is 3. For example, if the wheel is 30 inches in diameter the circumference would be Divide by 12 to get 7. Calculate wheel revolutions per mile by dividing 5, by the tire circumference in feet. The example tire will make Calculate the speed per minute by dividing the wheel speed by the tire revolutions per mile.

For example, if the wheel speed is rpm, the example tire is moving at 0. Multiply the miles per minute speed times 60 to convert the speed to miles per hour mph. Our example tire with a 30 inch diameter turning at rpm will have a road speed of This article was written by the It Still Runs team, copy edited and fact checked through a multi-point auditing system, in efforts to ensure our readers only receive the best information. To submit your questions or ideas, or to simply learn more about It Still Runs, contact us.

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Step 1 Calculate the circumference of the wheel in feet from the diameter. Step 2 Calculate wheel revolutions per mile by dividing 5, by the tire circumference in feet.

Step 3 Calculate the speed per minute by dividing the wheel speed by the tire revolutions per mile. Tip If the calculations need to be made numerous times, a spreadsheet can be set up with the calculations.

Then, only the tire diameter and speed in rpm need to be changed to calculate a new road speed. About the Author This article was written by the It Still Runs team, copy edited and fact checked through a multi-point auditing system, in efforts to ensure our readers only receive the best information.Enter your axle gear ratio, tire diameter, vehicle speed, and transmission gear ratio in the blue fields and click the calculate button to find your engine RPM.

Engine RPM, or the speed at which the engine turns, can be calculated at any speed given the vehicle's tire size, axle ratio, and final transmission gear ratio. This calculation is used to match oversize tires with new ring and pinion gears to obtain the desired engine RPM at highway speed. Note: Crawlpedia is proudly supported by Filthy Motorsportsa specialty off-road racing and 4x4 parts shop in Boulder, Colorado.

Want to see your banners and links on Crawlpedia? It's easy, affordable and very effective, just contact us to get started! To find the street legal laws for your state including maximum suspension lift heights and tire size rules visit LiftLaws. Engine RPM Calculator Enter your axle gear ratio, tire diameter, vehicle speed, and transmission gear ratio in the blue fields and click the calculate button to find your engine RPM. For Example: 2. Filthy Motorsports Crawlpedia is proudly supported by Filthy Motorsportsa specialty off-road racing and 4x4 parts shop in Boulder, Colorado.

Wheel And Tire Motion Calculator

Advertise Here! Street Legal Laws To find the street legal laws for your state including maximum suspension lift heights and tire size rules visit LiftLaws.

Axle Gear Ratio:. Vehicle Speed:. Engine Speed:. For 4x4 low range, multiply your transmission ratio by your transfer case ratio and use the result for your transmission ratio above.Use our gear ratio calculator to find the changes to gear ratio when going to a different tire size. Both the effective and new gear ratios are calculated. Use our gear ratio calculator to find the effective gear ratio your vehicle will have with a new tire size.

Also calculated is the new gearing you would need in order to return back to your original gear ratio when going to a bigger or smaller tire. Input your stock and new tires sizes along with your original gear ratio. Click "Calculate" to find your new effective gear ratio and the gear ratio needed to return your vehicle back to stock gearing.

Changing tire size will ultimately affect the power and drivability of your vehicle. If you are looking to retain your stock feel or change your gearing to the optimal ratio, then you will need this gear ratio chart to do so.

Using the chart, first cross reference your current gear ratio and tire diameter to find your approximate RPM at 65 MPH. Then reference your new tire diameter with your choice of RPM to find the new gear ratio needed to supply you with that RPM. This chart is based on a drive gear of at 65 MPH using a manual transmission.

Automatic transmissions will run a slightly higher RPM do to slippage. If you are using the calculated diameter, multiply that number by. If you are measuring your tire, measure from flat ground up to the center of the hub and multiply that number by 2.

Gear Ratio 2. Tire Size Tools. Tire Categories. Popular Sizes.Use our speedometer calculator to find the differences in speedometer reading and actual speed when changing to a tire size other than stock.

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Speedometer calibration, or knowing how fast you're going, can be pretty important. We all know a ticket is about the biggest buzz kill on earth! So if you're about to get bigger tires than stock or already have them installed, its time to calculate your true MPH. Your speedometer is reading how many revolutions your tires are making not how fast they are spinning. When you go to bigger tires the circumference of the tires is larger, meaning the distance around the tire is longer.

Thus, with each revolution you are traveling further than before. Therefore your actual speed is higher than your speedometer reads.

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Or lower if you have gone with a smaller tire than stock. Our speedometer calibration calculator will get you the answer you are looking for. Enter your original tire size, your new tire size, and then play with the miles per hour to see how much faster you are going at different speeds.

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If you would like to see more speedometer calibration speeds at a time, visit our tire size comparison page to compare different metrics of tires and get multiple speedometer calibration readings at once. Speedometer Calibration Tire Size Chart for Speed Calibration Tire Size Charts by Diameter 21" 22" 23" 24" 25" 26" 27" 28" 29" 30" 31" 32" 33" 34" 35" 36" 37" 38" 39" 40" ".

tire speed calculator rpm

Tire Size Tools. Tire Categories. Popular Sizes.Enter your tire size information into one side of the tire size converter below to convert metric tire sizes to inches or inch tire sizes to their metric equivalents. Enter your original tire size and gear ratio into the form below along with your new tire size to find your recommended ring and pinion gear ratio.

Enter the number of teeth found on your ring gear as well as your pinion gear in the boxes below to calculate their combined ring and pinion gear ratio. Full Calculator: Gear Ratio Calculator. Enter your transmission, transfer case, and axle gear ratios into the left side of the form below and press the calculate button to find your final crawl ratio.

Enter your original and new tire sizes into the table below and select a base speed to calculate your speedometer's offset and your vehicles actual speed. Enter your axle gear ratio, tire diameter, vehicle speed, and transmission gear ratio in the blue fields and click the calculate button to find your engine RPM.

Crawlpedia is proudly supported by Filthy Motorsportsa specialty off-road racing and 4x4 parts shop in Boulder, Colorado.

tire speed calculator rpm

Want to see your banners and links on Crawlpedia? It's easy, affordable and very effective, just contact us to get started! To find the street legal laws for your state including maximum suspension lift heights and tire size rules visit LiftLaws.

Ring and Pinion Gear Calculator Enter your original tire size and gear ratio into the form below along with your new tire size to find your recommended ring and pinion gear ratio.

tire speed calculator rpm

Gear Ratio Calculator Enter the number of teeth found on your ring gear as well as your pinion gear in the boxes below to calculate their combined ring and pinion gear ratio.

Crawl Ratio Calculator Enter your transmission, transfer case, and axle gear ratios into the left side of the form below and press the calculate button to find your final crawl ratio. Engine RPM Calculator Enter your axle gear ratio, tire diameter, vehicle speed, and transmission gear ratio in the blue fields and click the calculate button to find your engine RPM.

Filthy Motorsports Crawlpedia is proudly supported by Filthy Motorsportsa specialty off-road racing and 4x4 parts shop in Boulder, Colorado. Advertise Here! Street Legal Laws To find the street legal laws for your state including maximum suspension lift heights and tire size rules visit LiftLaws.

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Inch Tire Size x - Example: 35 x OEM Tire Diameter:. Recommended New Gear Ratio:.Leave us a question or comment on Facebook. Com All Rights Reserved. These calculators are designed to give the approximate engine RPM revolutions per minute based on data entered. That data consists of the ring gear and pinion gear ratio, the height of the tires diameter from ground to top of the tire while mounted on the vehicle and the transmission final gear ratio.

The default values are for a typical V8 small block Chevrolet vehicle, however you may enter any legal value you wish. The first calculator assumes you want all the possible transmission options and may not really know what you have. For the automatic selection, it assumes the transmission selector is in drive and not overdrive or lower gears. The AOD is for automatic overdrive in that selected position.

Manual is for a three speed non-automatic transmission in the last gear, or for a four speed transmission in fourth or a five speed or higher transmission in the next to final gear. The five speed option is for the last gear of a transmission greater than four speeds.

How to Calculate Speed Based on Wheel Speed & Tire Diameter

The higher the RGP ratio, the lower the top end speed but faster acceleration and more pulling power. The same is true of the transmission final gear ratio.

Although there is a point of diminishing returns, the larger the tire diameter, the higher the potential speed. We do assume safe tire air pressure and tread. The calculator does not take into consideration any drive train loss, road and weather conditions or driver skills. The calculated results are displayed; the higher the engine RPM, the greater the potential speed at the cost of fuel, heat, friction and engine longevity.

We urge you to drive safely. You can find different car stereo systems for just about any vehicle like the Camaro or the Toyota Supra when you shop online. Car audio systems can be customized for many different cars. Search or Browse Our Site.Note: The calculator will not work because Javascript is not enabled in your web browser.

There is a potential source of error in these calculations due to centrifugal force expansion of the tire at high speeds. While that effect may often be negligible for radial-ply tires due to the circumferential belts used in their construction, to get the most accurate results especially using bias-ply tires users should check with their tire manufacturer to determine how much the tire radius or revolutions per mile will change at various speeds.

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Another potential error source in these calculations is when the engine RPM is not identical to the RPM of the transmission input gears. For example, using this calculator for a vehicle having a torque converter such as an automatic transmissionor using this calculator for a vehicle with a slipping clutch may produce incorrect results. In such cases, the engine RPM may be significantly higher than the RPM delivered to the transmission gears, and the calculated vehicle speed will then be significantly higher than the actual speed.

On the other hand, if the torque converted is fully locked, or if the clutch is not slipping, these calculations should be reliable. For those who are curious about the calculations, here are the gory details of the speed versus engine RPM calculations:. Each revolution of the engine is reduced by the transmission gear ratio, each revolution of the output shaft of the transmission is reduced by the rear-end ratio, and each revolution of the tire makes the car move a distance equal to the circumference of the tire.

Pretty simple really. Transmission Gear Ratio R1 : denotes how many engine revolutions there are for each driveshaft revolution. Differential Gear Ratio R2 : denotes how many driveshaft revolutions there are for each axle revolution. Vehicle Speed.