Bike tire sizing is one of the most ignored aspects among casual riders.
Most riders just kind of go along with whatever comes with their bike, or leave things up to their local bike shop whenever it's time for a replacement or upgrade.
Things can get a little tricky if you're doing things on your own, however. If you're someone who plans on shopping online for new tires, or if you're considering changing sizes, it's obviously a requirement to know what the sizes are in the first place.
Almost every tire has the size printed on the outside, but these numbers can wear off over time, so if you don't have your sizes memorized, you may be in trouble if you don't know how to measure.
Measuring a tire is actually much easier than you think, and there are quite a few different ways to do it. This post will walk you through a common method.
Wait...What do the Numbers Mean?
Before measuring, it’s good to know what the numbers indicate in the first place. Bicycle tire measurements have two different parts.
The larger number is the tire diameter, while the smaller number is the tire width. This is commonly done using inches, although millimeters can be used as well.
Different bike types use vastly different sizes. Most tire diameters generally fall between 12 to 26 inches, with tire widths normally ranging from 1.75 to 2.215 inches.
Ok, onto the actual measuring.
ways to measure your tire.
The standard method
Lean the bike against a wall or use the kickstand to keep it upright. You can measure the bike wheel without the bike tipping over you if the bicycle is upright. If you're measuring the bike by yourself, a retractable metal tape measure is of more durability than a plastic tape measure while still allowing you to use your other hand.
Measure the distance in inches between the ground beneath the tire and the wheel's center point. The wheel's radius, or half of its diameter, is this measurement. To get the tire's diameter, multiply the length by two. Most adult bicycle wheels are between 26 and 29 inches in diameter except for BMX cycles or mountain bikes.
From one side to the other, measure the flat section of the tire across the tread. The breadth of the tire is the distance. It varies widely depending on the intended application of the tire. The rougher the expected terrain, the broader the tread, while narrower tracks guarantee a smoother, faster ride.
Place the diameter first, followed by the breadth. When buying a new tire, remember that traditional or standard sizes put the diameter first, then the breadth.
The ISO method
Check to see if the ISO standard is used to measure the wheels on your bike. Millimeters are used by the International Organization for Standardization (ISO) to measure the diameter of your bicycle's wheel.
The most reliable method for measuring your tires at home is ISO sizing. It should provide you with the most precise measurement.
The standard and ISO methods are used to measure the majority of tires. Their sizes should also be printed on the tire's sidewall so that you can quickly inspect them.
Make sure the bike is parked against a wall or on its kickstand. Measure in millimeters from the wheel's center to the tire's inner edge only. To find the diameter, multiply the figure by two.
The ISO standard comprises both the bead seat diameter (BSD) and the tire width in millimeters.
In millimeters, measure the breadth of the tire. Using the same procedure as before, go from one side to the other. Remember that different width tires can be used on the same bicycle wheel as long as the difference isn't too great.
Calculate the circumference of the bike's wheel
Take a circumferential measurement. The circumference of a bicycle wheel is the distance around the outside of the wheel that you need to calibrate a bicycle speedometer, odometer, GPS, or computer appropriately. Bicycle equipment must be configured based on the size of your tires, much as your car's speedometer and odometer will offer false data if you change the size of its wheels. You'll need to determine the circumference of the wheel whether you've recently acquired a cyclometer or need to calibrate an existing one since you've moved to tires with a different thread size.
To get the circumference, multiply the tire's diameter by pi that is 3.14. If you already know the tire's diameter from one side to the other, you can calculate the circumference of any circle rapidly.
If you already know the diameter and breadth of the tire, you can use one of several online calculators to calculate the circumference.
Using a string, measure the circumference. If you don't know the diameter of the wheel, you can still estimate its circumference by looping a rope evenly around the tire's outside edge. To determine the circumference, mark or cut the thread to reach back to its beginning place and measure its length.
Apply a dot of wet paint to the tread of a bicycle tire. Push the bike in a straight line for at least two spins, ensuring that the color is on the ground twice. To estimate the tire's circumference, measure the ground from one paint spot to the next.
Check Bike's Manual
The specifications manual that came with the bike will most likely have your wheel sizes listed. If this is not the case, contact the bike store where you purchased your bike and they will be able to assist you.
Alternatively, go to the retailer's website and look up the bike's specifications. The wheel size should be listed in the specs section.
Stand the bike up using a kickstand, or just lean it against a wall.
Step 2: Diameter
Place a tape measure against the center of the bicycle wheel, and then extend the tape in a straight line towards the tire’s outer edge.
If you’re using traditional sizing, all you need to do is double the length that you just measured, and you have the diameter.
(Keep in mind that tire diameters are almost always whole numbers. So, if your measurement comes out to something like 25.8, the actual diameter is really just 26 inches.)
Step 3: Width
Measuring width is just as easy. Take your tape measure, and place it on flat surface across the tire's tread going from one side to the other side.
Now all that’s left to do is to combine the measurements. Standard bike tire sizes place the diameter first and the width second. So, if your diameter was 26 inches, and the width came out to 2.2 inches, the printed measurement would be 26 x 2.2.
See? That wasn’t as hard as it initially seemed. You should now be able to accurately measure your bike’s tires whenever the need arises.
If you’re looking to use different sizes than what originally came on your bike, check to make sure your fork and frame can accommodate the size.
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