# How to calculate bicycle wheel size

Bike Computer – Tire Size Calculator

rows · (The logical version) Given rim diameter (the ISO diameter) and tire diameter (the size of your tire converted to millimeters) Wheel diameter = (rim diameter) + (tire diameter * 2). Wheel circumference = Wheel diameter * PI. Since the tire wraps around your . Bike Computer – Tire Size Calculator INCHES TO MM CONVERTER. If your wheel size isn’t listed in in the drop down above, you can just enter the number into APPROXIMATING WHEEL SIZE USING LINEAR INTERPOLATION. The numbers in the calculator above rarely match what’s in any ROLLOUT TEST. Another.

Thanks for visiting! I thought it was a totally different size. If you have inches and need mm, enter them in the following box:. Should you be unable to locate the manual most manufacturers have their manuals available online. Get it? Another way to calcilate your wheel size without any calculations at all is to measure the distance you travel in one revolution of the tire with it inflated to the pressure you normally would use.

This is easier said than done. Two suggested ways to do this are:. If you computer read too calculaye, maybe 1. Bike Computer — Bicyle Size Calculator. You can watch this video for more info or just scroll down and start using the calculator.

Wheel Size Size Dia. Two suggested ways to do this are: Blcycle Sit on your bike next to a wall. Roll forward till your valve stem is at the bottom of the wheel. Have a friend mark that spot with tape of chalk.

Roll forward one revolution of the wheel so the valve stem is at the bottom of the wheel again. Mark that spot with tape of chalk. Measure the distance between the two marks in mm.

Paint or Water Put a blob of wet paint on the pavement. Ride over it and keep riding. Each time your tire hits the pavement again, it should leave a mark. You should be able to measure the calcultae between marks or between multiple marks for even what is a brand value proposition accuracy. Measure that distance in mm.

INCHES TO MM CONVERTER

Paint or Water Roll. Put a blob of wet paint or water on the pavement. Ride over it and keep riding. Each time your tire hits the pavement again, it should leave a mark. You should be able to measure the distance between marks (or between multiple marks for even greater accuracy). Measure that. To calculate your bike frame size, take your inseam in centimeters and multiply it by for mountain bikes, for road bikes, and for trekking bikes. If you need to convert your measurements to inches, divide them by 42 rows · Hook the tab into the valve hole and wrap the tape all the way around the rim, .

Note: this article is about how to measure rims for tires. We have another article which describes how to measure rims for spokes. What size tire do you need to buy for your bicycle? There are so many different tire sizes and different systems for marking tire sizes that have been used over the years that this is often a serious problem, especially for older bicycles.

We have a major article on this web site explaining the different tire sizing systems. But what do you do if you don't have the original tire, or if the markings are not legible? All is not lost! Bead Seat Diameter. You can measure either the diameter or the circumference. Lay your measuring tape or ruler across the rim from one side to the other. Get the largest measurement, between two points directly opposite one another. Slide one end of the tape back and forth along the rim until the measurement is largest.

Measure across a few different diameters and take the average, in case the rim isn't quite round. If it's way out of round, don't use it. If it's a millimeter or two out of round, the spokes will pull a shallow-section aluminum or steel rim into shape -- not so much for a deep-section carbon-fiber rim..

Next you get out your pocket calculator or smartphone app, or old-school paper and pencil. Multiplying by The table below gives common and uncommon rim sizes with the corresponding bead seat circumference dimensions.

If you are working with an empty rim, it is easiest to measure the diameter, but if you have a built-up wheel, the hub will get in the way of the tape measure, making it difficult to get an accurate measurement. For a built-up wheel, it is easier to measure the rim's circumference. It may also be helpful to take a circumference measurement to confirm that the diameter measurement was correct.

You may measure the circumference of a rim by wrapping a measuring tape all the way around the rim. You derive the diameter from the circumference. A wide metal tape measure won't fit into the well of the rim and and won't curve smoothly around the rim.

Don't trust a fabric measuring tape as used in fitting clothing. This kind is usually inaccurate, because the fabric stretches. If you don't have a narrow tape measure, you could wrap a length of thin, flexible electrical wire or bicycle cable inner wire around the rim, mark two places on the wire which line up with one another, lay the piece out flat and measure the distance between the two marks.

Our example rim is a hook-edge rim without clearly-defined bead seats, so we'll measure from the well but not the bottom of the recessed spoke holes to the outside of the rim and then subtract twice the typical flange height.

Our highly-sophisticated tool for this task is a bicycle spoke. We are also using a small ruler as a bridge across the rim flanges. Holding the spoke with a thumbnail against the ruler gives us a good enough measurement for our purposes.

This article has featured common, inexpensive and improvised tools. More sophisticated tools such as a caliper with a depth gauge can make the work go faster. Measuring rims involves some elementary-school or pocket-calculator math. Sheldon quoted Robert Heinlein at the end of the article:. More about that quote. OK, so Heinlein actually, a character in one of his books said that, and Sheldon quoted that, but anyone who cannot accept that other people have different abilities and educational opportunities shows an unfortunate lack of compassion!

I'm hoping that this article provides an easy guide to some practical math, and helps to dispel math anxiety.

Also, a longer discussion of the Einstein quote is online, in case you're interested Accessories Bicycles Parts Specials Tools. Translation of this article earlier version : Macedonian. One measurement is worth 50 expert opinions.

Diameter Circumference Tools About Math. Instructions on measuring using the circumference are below the table. Use the metal tape measure as shown in the image below. Here are the steps to measure using the circumference: The tape has a tab at the end.

Hook the tab into the valve hole and wrap the tape all the way around the rim, measuring the total circumference at the bottom of the well. Divide the circumference by pi 3. If the tape measure is divided in inches, also multiply by Add twice the height from the well to the bead seats see instructions below. Anyone who cannot cope with mathematics is not fully human. At best he is a tolerable subhuman who has learned to wear shoes, bathe, and not make messes in the house.

But also there's this:. I can assure you mine are still greater. Tweet Follow sheldonbrowncom. Most newer adult bikes for road use use this size, including most road bikes and hybrids. Also C tubular. Schwinn " lightweights ", older English " club " bikes. Most 3-speeds except Schwinn; department-store or juvenile 10 speeds. French utility bikes, tandems, and loaded-touring bikes; some mountain bikes.

This size is currently undergoing something of a renaissance. Some 26" tubulars. Oddball size formerly used on some GT models.

Not available. Note: D is often incorrectly identified as mm bead seat. Most mountain bikes , cruisers , fatbikes. British juvenile, most wheelchairs.

French A is mm, close enough. Saavedra 25" tubular. High-performance wheels for smaller riders; Terry front, most 24" tubulars. Rare Schwinn juvenile, specialty racing bicycles, older Easy Racers recumbents. Most BMX , juvenile, folders, trailers, some recumbents. Alex Moulton AM series, 18" tubular for specialty racing bicycles. Rare Schwinn juvenile. Probably the same rim diameter as 16" tubulars.

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