Lawn mower belt calculator. How to Measure Your Pulley

How to Measure Your Pulley

In this article, we explain how to best measure the most important dimensions of your pulley or sheave so you can find the best replacement possible. We also explain what many of the terms and specs mean that you may see when you’re looking for a pulley or sheave. For a more detailed description of terms AND reference diagrams, check out our blog post here: Pulley Dimension Definitions

Once you know how to measure your pulley, shop for the right one on our site get 10% off your order. Promo code is at the end of this article!

How Do I Measure My Pulley and Find the Right One To Buy?

The most common measurements used to find the right pulley or sheave are the outside diameter, inside diameter and the width. There are also a few other measurements that are helpful to know in order to find the right size pulley or sheave for your needs.

It’s important to us that you can find a pulley that matches your specs as closely as possible. which may seem tricky when shopping online but here at TERRE Pulleys, Bearings Belts. we make it easy for you to find the right pulley and we offer Fast Free Shipping on nearly all of our items! Below we explain how to measure various dimensions so you can find the right pulley and get it quickly!

Note: We will be referring to pulleys going forward. but this information can be used for sheaves as well. These terms are often used interchangeably. to us sheaves are pulleys and pulleys are sheaves.

Measuring Pulley Outside Diameter

Also Known As OD, length, breadth

Place your pulley face down on a flat surface, then put your ruler or caliper on top, measure from outside edge to outside edge across the circle of the pulley.

The above pulley has an outside diameter of 4.5”

Check carefully to make sure you are measuring across the center. One trick is to hold one side of your ruler still and rotate the outside edge around. the outside diameter is always going to be the longest dimension you measure.

To find a drive pulley based on the Outside Diameter, click FIND A DRIVE PULLEY and use the Outside Diameter filters on the left-hand side of the page to find the right size!

You can also find V-Groove Idler Pulleys the same way by clicking FIND A V-GROOVE IDLER PULLEY.

NOTE: If you have a Flat Idler. you may want to locate the right size based on the Flat Diameter instead of the total Outside Diameter. If you have a flat idler, check out the next section!

Measuring Pulley Flat Diameter

Also Known As: belt diameter, face diameter

You only need to get this measurement if you are using a flat idler pulley.

This is the diameter of the pulley where the belt rides. If your flat idler does not have flanges keeping the belt in place, then the Flat Diameter will be exactly the same as the Outside Diameter.

However, if your pulley has flanges, your flat diameter will be smaller than your outside diameter. If your flat idler does have flanges, you can try and guesstimate the flat diameter by measuring the diameter the same as you would the outside diameter, just try to measure as if the pulley does not have flanges.

To be more precise, you can wrap a string tightly around the flat of the pulley where your belt rides. Mark the string where they overlap, then measure its length. Divide that number by 3.14.

In this flat idler, the string measured 10 1/4”. Typing 10.25÷3.14 into a calculator gets you 3.26, so the flat diameter is about 3 1/4”.

No calculator on hand? You can use your browser’s search bar!

Now that you have your idler pulleys Flat Diameter, use that information to filter to the right size Flat Diameter here: FIND A FLAT IDLER PULLEY

Measuring Pulley Width

Measure from side to side across where your belt sits, from outside edge to outside edge. The width dimensions on our site do not include the hub of your pulley.

Measuring Pulley Flat Width

This dimension is only needed for measuring flat idlers and drives.

Calipers work best for measuring this dimension.

If you don’t have calipers, you will need to measure the width between flanges from inside edge to inside edge using a ruler and eyeballing it. If your pulley has flanges, the flat width will always be narrower than the overall width. Some flat idlers have a wide angle on their flanges – this helps your belt last longer, but does make it even trickier to measure accurately.

Is this being used as a backside idler? Try also checking the widest part of your belt. If it’s a 5L or B belt, for example, then the flat of your pulley will need to be about 7/8” or bigger.

Left: A ruler is used to measure the flat width.

Center: Even inexpensive calipers can make measuring your parts so much easier.

Far Right: A pulley being used as a backside idler. The flat side of the belt is making contact with the flat surface of the flat idler.

Measuring Inside Diameter of Pulley

Also Known As: Bore, center hole, bolt size, shaft size.

Measure across the center hole of your pulley. Do not include any keyway in your measurement.

If you know your drive pulley is running on a 1 shaft, or that your idler pulley uses 3/8 bolts, then it’s safe to assume that the inside diameter is the same as the shaft or bolt diameter.

To find the pulley with the right inside diameter, click on either the drive pulley or idler pulley link below and then filter to the desired inside diameter on the left-hand side of the product page.

Note : Idler Pulleys often can have their inside diameters easily customized by selecting a bore adapter! For more information on this, contact us at [email protected] or 1-800-776-9315 or visit this helpful blog post: How to Use Multiple Bore Adapter Options

Measuring Pulley Frontside and Backside Offset:

The offset is the distance from the centerline of the pulley to the outside edge of the bore. On a V-groove drive, for instance, the centerline or “middle” of a pulley would be the lowest point of the V, and you would measure from there to the edge of the hub. Generally, the “frontside offset” is the longer of these dimensions, while the “backside offset” is the shorter.

This is tricky to get if you can’t cut your pulley in half, so the good news is you probably won’t need it.

Measuring a Pulley’s Keyway

A keyway is a notch made into the hub from the inside hole of a drive pulley and is where your key will be inserted to lock the pulley in place on the shaft. Most keyways are standardized to the shaft your drive pulley goes onto.

Shaft Size/ Inside Diameter

If you have your key on hand, measuring that is certainly the most precise option. Otherwise, a ruler works fine.

Measuring Pulley Pin Diameter

In the pulley world, a “pin” is a precisely-cut cylinder that links to the engineering standards of a specific belt type. During the design process, pulleys are “married” to a pin size which will be used in design processes for new equipment.

Did any of that make sense? No? No problem, because all most of us will need to know is the following:

Belt Type the Pin is used for

IMPORTANT: Having a pin diameter of 0.5625 does not mean that a 4L belt will not work, it just means that the pulley was not necessarily designed with that belt type in the mind of the engineer. Check in the “Belts that fit” section to see if your belt is listed on the pulley you are considering.

Measuring Pulley Overpin Diameter

This is yet another highly technical dimension that you will probably not need to find the correct pulley, but for reference, we’ve included information on this dimension for you:

If you place two pins on either side of the grooves on a v-belt pulley and measure the distance, you will get the Overpin diameter.

How you can use this, though, is a tool to visualize how far into a groove your belt might ride into the v-belt pulley you’re considering.

For instance, if the Outside Diameter is 7”, but the Overpin Diameter shows 7.35” then the belt is riding at the top of that pulley. Look at another 7” pulley, and the overpin shows 6.5. Now we’re looking at a belt that rides pretty deep into that groove.

Another way to consider this is by looking at different belts inside the same groove:

In a 7 pulley with this kind of groove, a 3L belt has a pin diameter of 6, while a 5L belt is at 6.8. If your original 3L belt was riding higher up in the groove of your original 7 pulley, then using a pulley with a 0.5625 pin will give your belt some slack that you might not want.

A neat rule-of-thumb to try is that you can subtract one pin diameter from the overpin diameter, to get the datum, or the estimate for where the center of the belt should ride.

Stickout

Note: Some places use stickout as a synonym of Offset, we find that to be less useful.

How far does your bore “stick out” from the edge of your pulley? Place the pulley face down, with the longest part of the bore resting on the table.

One of the easiest things to measure, so long as your ruler’s marks go all the way to the edge instead of stopping early.

Place your pulley, longer part of the bore pointed down, and measure from the table to outside edge of the pulley’s flange.

The pulley all the way to the right has a negative stickout which means the bore doesn’t even reach the edge of the pulley.

The stickout is particularly useful for when you are bolting an idler up and don’t want the flanges to come into contact with anything.

Measuring Pulley Throughbore

Measure from one end of your bore through to the other side. If you only have a thick ruler, try using a toothpick or pencil.

When you have a negative stickout, you can’t just put your pulley down on a table and successfully obtain a throughbore, so make sure to check the back side.

Now that you are an expert on how to measure a pulley. let’s find you the right part!! Use the navigation along the top of the page or select from these popular categories:

BONUS : Ready to find that pulley? Enjoy 10% off your first order by entering promo code MEASURE at checkout!!

Did we miss anything? Still confused? Email us at [email protected] or call 1-800-776-9315. our team of experts is happy to help!

O’Reilly Auto Parts Store Services

Most O’Reilly Auto Parts locations can resurface your vehicle’s drums and rotors if they measure within specs and aren’t showing signs of extreme wear. Surface finish is crucial to proper vehicle braking and pad life and should always be part of a complete brake job. Please contact your local O’Reilly Auto Parts store for pricing and availability on drum and rotor resurfacing.

Battery Testing. Free

Extreme temperatures in both winter and summer play a large part in battery failures. Bring your battery into any O’Reilly Auto Parts store for a complete diagnostic check at no charge. Our Parts Professionals can test your battery, and if it’s about to fail, help you find the right Super Start battery for your needs.

Alternator Starter Testing. Free

Alternator: To maintain the battery and keep up with the electrical system demands of your vehicle, the alternator has to put out between 13.5 and 14.8 volts. If you are having charging system issues and suspect the alternator, your local O’Reilly Auto Parts store can test it, on or off the vehicle, to determine where you may have a problem.

Starter: Starting system problems are common, but not all problems are caused by a faulty starter motor. If you are having intermittent starting problems, stop by your local O’Reilly Auto Parts store and let us test your starting system. If the vehicle won’t start and you suspect the starter is the problem, bring the starter in and our Parts Professionals can bench test it.

Wiper Blade Bulb Installation. Free

Our Parts Professionals will install wiper blades and replacement bulbs free of charge (with purchase of wiper blades or bulbs). Whether you’ve bought front or rear wipers (or both), headlights or tail lights, we’d be happy to install them for you.

Restrictions apply. See your local store for details.

Bilingual Team Members

Our team members are here to provide great customer service. We are proud to say that in some locations we have bilingual team members who will help you find the parts you need. The additional languages vary store- to-store. Check the services offered at the store nearest you.

Loaner Tool Program

Many vehicle repairs require tools that will only be used once. The O’Reilly Auto Parts Loaner Tool Program is available at all of our locations, covering a wide range of tools that cover almost any job. A deposit is required which is fully refundable once the tool is returned. See available loaner tools

Custom Paint Mixing

Collision repair professionals and do-it-yourselfers alike turn to O’Reilly Auto Parts AutoColor for unmatched quality and service. O’Reilly Auto Parts stocks industry-leading products such as 3M, Evercoat, Hutchins, Nason and Sata among others.

• Over 500 O’Reilly AutoColor custom paint mixing locations across the US
• A full line of automotive, custom, fleet and industrial paint
• One of the nation’s largest inventories of auto body equipment and supplies

Check Engine Light Testing. Free

A check engine light is often the first warning of a potential problem. O’Reilly Auto Parts offers free check engine light testing to help you diagnose the problem. Most of our stores can loan you a code reader for OBD 12 systems for vehicles from 1996 and up, except in areas where it is prohibited by law. Also, our stores now offer Trouble Code Support, and they can provide you a print out to identify your code. Further diagnostic or repair service is not offered, but our stores are happy to refer you to a local professional. For more details on the loaner code reader and Trouble Code Support, please call your local O’Reilly Auto Parts store.

Custom-Built Hydraulic Hoses

O’Reilly Auto Parts has over 1,300 locations that can custom-build hydraulic hoses. Whether you have a hay baler or a forklift, O’Reilly Auto Parts has hoses and fittings to help you complete the job.

• 2 wire low-pressure, 4 wire high-pressure 1/4- 3/4 and in several locations up to 1-1/4
• A full line of Gates fittings, hose and equipment to make or repair your own hoses
• Hydraulic fluids in 1, 5 and 55-gallon quantities
• Non-conductive hose and fluid available for specialty applications

Fluid Battery Recycling. Free

O’Reilly Auto Parts collects used motor oil, automotive batteries, transmission fluid, gear oil and oil filters for recycling.- free of charge!

• Get it taken care of hassle-free
• Thousands of convenient locations
• 10 O’Reilly Gift Card for any unbroken automotive battery you may have
• Absolutely free

It is required that containers are returned to customers. Environmental laws can vary by state and city and in some municipalities some stores cannot recycle oil. It is best to contact your local O’Reilly Auto Parts store for availability and details. Used antifreeze/coolant is considered hazardous waste so we are unable to recycle it in our stores. Most cities and counties have hazardous waste collection sites. We suggest calling your city or county administration or search their website for hazardous waste disposal. (Other restrictions may apply)

Not all services offered at every location. Check your local store for available services and more details.

O’Reilly Auto Parts Store Services

Most O’Reilly Auto Parts locations can resurface your vehicle’s drums and rotors if they measure within specs and aren’t showing signs of extreme wear. Surface finish is crucial to proper vehicle braking and pad life and should always be part of a complete brake job. Please contact your local O’Reilly Auto Parts store for pricing and availability on drum and rotor resurfacing.

Battery Testing. Free

Extreme temperatures in both winter and summer play a large part in battery failures. Bring your battery into any O’Reilly Auto Parts store for a complete diagnostic check at no charge. Our Parts Professionals can test your battery, and if it’s about to fail, help you find the right Super Start battery for your needs.

Alternator Starter Testing. Free

Alternator: To maintain the battery and keep up with the electrical system demands of your vehicle, the alternator has to put out between 13.5 and 14.8 volts. If you are having charging system issues and suspect the alternator, your local O’Reilly Auto Parts store can test it, on or off the vehicle, to determine where you may have a problem.

Starter: Starting system problems are common, but not all problems are caused by a faulty starter motor. If you are having intermittent starting problems, stop by your local O’Reilly Auto Parts store and let us test your starting system. If the vehicle won’t start and you suspect the starter is the problem, bring the starter in and our Parts Professionals can bench test it.

Wiper Blade Bulb Installation. Free

Our Parts Professionals will install wiper blades and replacement bulbs free of charge (with purchase of wiper blades or bulbs). Whether you’ve bought front or rear wipers (or both), headlights or tail lights, we’d be happy to install them for you.

Restrictions apply. See your local store for details.

Bilingual Team Members

Our team members are here to provide great customer service. We are proud to say that in some locations we have bilingual team members who will help you find the parts you need. The additional languages vary store- to-store. Check the services offered at the store nearest you.

Loaner Tool Program

Many vehicle repairs require tools that will only be used once. The O’Reilly Auto Parts Loaner Tool Program is available at all of our locations, covering a wide range of tools that cover almost any job. A deposit is required which is fully refundable once the tool is returned. See available loaner tools

Custom Paint Mixing

Collision repair professionals and do-it-yourselfers alike turn to O’Reilly Auto Parts AutoColor for unmatched quality and service. O’Reilly Auto Parts stocks industry-leading products such as 3M, Evercoat, Hutchins, Nason and Sata among others.

• Over 500 O’Reilly AutoColor custom paint mixing locations across the US
• A full line of automotive, custom, fleet and industrial paint
• One of the nation’s largest inventories of auto body equipment and supplies

Check Engine Light Testing. Free

A check engine light is often the first warning of a potential problem. O’Reilly Auto Parts offers free check engine light testing to help you diagnose the problem. Most of our stores can loan you a code reader for OBD 12 systems for vehicles from 1996 and up, except in areas where it is prohibited by law. Also, our stores now offer Trouble Code Support, and they can provide you a print out to identify your code. Further diagnostic or repair service is not offered, but our stores are happy to refer you to a local professional. For more details on the loaner code reader and Trouble Code Support, please call your local O’Reilly Auto Parts store.

Custom-Built Hydraulic Hoses

O’Reilly Auto Parts has over 1,300 locations that can custom-build hydraulic hoses. Whether you have a hay baler or a forklift, O’Reilly Auto Parts has hoses and fittings to help you complete the job.

• 2 wire low-pressure, 4 wire high-pressure 1/4- 3/4 and in several locations up to 1-1/4
• A full line of Gates fittings, hose and equipment to make or repair your own hoses
• Hydraulic fluids in 1, 5 and 55-gallon quantities
• Non-conductive hose and fluid available for specialty applications

Fluid Battery Recycling. Free

O’Reilly Auto Parts collects used motor oil, automotive batteries, transmission fluid, gear oil and oil filters for recycling.- free of charge!

• Get it taken care of hassle-free
• Thousands of convenient locations
• 10 O’Reilly Gift Card for any unbroken automotive battery you may have
• Absolutely free

It is required that containers are returned to customers. Environmental laws can vary by state and city and in some municipalities some stores cannot recycle oil. It is best to contact your local O’Reilly Auto Parts store for availability and details. Used antifreeze/coolant is considered hazardous waste so we are unable to recycle it in our stores. Most cities and counties have hazardous waste collection sites. We suggest calling your city or county administration or search their website for hazardous waste disposal. (Other restrictions may apply)

Not all services offered at every location. Check your local store for available services and more details.

PRODUCTIVITY CALCULATOR

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Step 1. Your Mowing Habits.

Don’t know what to put? Just make your best guess based on your current mowing habits, or how you would like to mow with a Walker mower if given the opportunity.

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Walker has gear driven decks and belt driven decks available. This large variety of decks available that make the Walkers a very customisable machine.

The decks range from 36”-74”

There is a range of collection, discharge, and mulching decks (even a 3 in one deck) and mulch kits are available for many of the decks. You can see what decks are compatible with the machines on the product pages.

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Read more about the GHS system within the Walker Advantage.

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Quality is not compromised in this process so you can still brig the Walker quality home without the commercial price tag.

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The Walker is designed to make mowing fast easy and efficient whilst leaving a beautiful cut.

The Commercial Mower range will increase your productivity, your job turnover rate, and overall performance, leaving you with better results in shorter times.

Calculate just how much of an increase in your productivity you can achieve with our productivity calculator.

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