What is my wheel size?

We custom-make each kit to fit your bike. Our kits can convert almost any bike into an eBike, as long as it doesn't have thru-axles. When you place your order, we will ask you for your wheel size (ETRTO number). 

If you are not sure what your wheel size is, you can use one of the options below to find out:

Check the Tyre Markings

Measure the wheel size yourself

Check your Bike Manual

Check tyre markings

Most bikes have their ETRTO wheel size marked on the side of the tyre. The image below shows you where to find this number. You may find you have the French or English tyre markings as well. This is the best way to identify your wheel size.


Wheel sizes have been measured in a variety of guides for some time now. At Swytch, we measure our wheel sizes by ETRTO number, a 5-digit number of the form ## - ### which tells you the precise diameter. 



The first two digits of the ETRTO denote the tyre width in mm. Swytch wheels can take any width tyres from 1.1-2.5 inches (28-64mm).

The last three are the inner tyre diameter. Your Swytch Wheel size will match the last three digits of this marking. For example, the marking 47-622 means that the 622 Swytch Wheel would fit this tyre. Once you find the tyre markings, you can use the table below to match it to the Swytch Wheel size.


So, if your wheel size is 32-622, then it has a width of 32mm (inside our 28-64mm range) and a diameter of 622, which is the 28” wheel. 

Other than ETRTOs, wheel sizes can be written in inches, as Diameter x Width (for example, 28x1.75). 



The wheel sizes 28”, 700C and 29er or 29” all refer to the same rim size: ETRTO 622.

The tyres can differ, but the 28”, 700C and 29er are all the exact same rim diameter. The 700 markings will be followed by the width in mm, and the 28 or 29 markings will be followed by the width in inches. This is the most common wheel size, so look out for familiar markings (such as 28x1.75, 700x32C, 29x1.50). 

Which 26” or 20” am I?

There are two 26” sizes and two 20” sizes. For each of these, they are differentiated by their ETRTOs, or by the style in which they’re written. 

The most common ones are the 26” (ETRTO 559) or the 20” (ETRTO 406). You can tell these because the widths are written as decimals, for example, 26x2.00 or 20x1.50

More rare are the 26” (ETRTO 590) or the 20” (ETRTO 451). You can tell these because the widths are written as fractions, for example, 26x1-3/8 or 20x1-1/8



Measure the Wheel Size Yourself

If you can’t find the size markings on the tyre, then you can measure the wheel yourself. By measuring the diameter of the rim in mm, you can calculate the approximate equivalent of the ETRTO number.

A quick lookup of bicycle wheel size name and rim diameter/ /ETRTO is below:
Wheel Size Rim Diameter / ETRTO
28" 29er 700C
27" / 27.5" / 650C 584mm
26" / 650C 559mm
24" 507mm
20" 451 (old style) 451mm
20" 406 406mm
16" 349mm


You can also measure your wheel size using the following four steps:


Step 1) Place the tape from the centre of the wheel to the tyre's inner edge where it meets with the rim. See the red line in the below image. Make a note of this measurement in mm. This is the inner radius of the tyre (R). [E.g. 317mm]

Step 2) Multiply this number (R) by 2. You now have the diameter of the rim. [E.g. 317x2 = 634mm]

Step 3) Subtract 10mm from the diameter. [E.g. 634-10 = 624mm]

Step 4) Match your measurement with the nearest wheel size in the table above - it should come within ±3mm. [E.g. 624mm = 622 Swytch Wheel]


Check your Bike Manual

Your wheel size often can be found in the specifications manual that came with the bike. If not, contact the bike shop where you bought your bike and they will be able to tell you.

Alternatively, check the bike details on the retailer's website. There will be a specifications section that should list the wheel size.


Still Not Sure? Contact Us

If you aren’t sure which size you need, you can still place your pre-order when the launch goes live. Once your order is in our system, we'll invite you to our order portal to confirm your bike’s specifications. This gives you a few extra days where we can help you check which wheel you will need.

If you have any further questions, please get in touch via email or open a support ticket.


Sign-Up To Pre-Order

Sign up now to join the pre-order waitlist to place your order with 50% off at our next launch.

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