Where to start?

The world of wheels can be a confusing one! You may have heard the terms 26 inch, 650b, 700c and 29er when referring to wheels but what does it all mean?

MTB Wheels

When we are talking about mountain bike wheels we tend to use inches as a standard for wheel size. 26 inch wheels where the most common for a long time, only being replaced with 27.5 inch and 29 inch wheels relatively recently.

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Road Wheels

Road wheels are more commonly referred to using the International Organization for Standardization (ISO) measuring system, which is in millimetres. The most common size for road bikes is 700c, you might also see 650b or 650c.

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What size is my wheel?

Your first place to check when working out your wheel’s size should be the rim, some manufacturers print the size on to the stickers on the rim! If there is nothing there then the tyre is the next place to check, if the bike is brand new then you may find the wheel size printed somewhere on the frame. If you have checked all the obvious spots and couldn’t find your wheel size then you will have to measure it!

Measuring it...

The way to measure a bikes wheel using the ISO system is to measure from the centre of your hub to the outside of your rim. You can then use the handy chart below to convert it to the most common sizes.

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Size guide

Wheel Size
ISO length (mm) Inches (MTB size) Road Bike size
305 16  
406 20  
507 24  
559 26 650c
584 27.5 650b
622 29 700c

Some key points about wheel sizes...

  • Mountain bikers might refer to 27.5 inch wheels as 650b, these terms are interchangeable when referring to a mountain bikes wheel!
  • You will likely never hear a mountain biker referring to there 29 inch tyres as 700c however, and visa versa for road cyclists!
  • 24 inch wheels tend to be used for children’s bikes and dirt jump bikes.
  • BMX’s tend to have 20 inch wheels.
  • A wheel’s size may be followed by another number, this refers to the tyres width. For example ‘700 x 35c’ or ‘27.5 x 2.10’.