My bike is a Genesis Day One 2011 originally Alfine 8 hub, only thing is I bought it as a fixie without the hub. I wish to purchase an Alfine 8 hub and wheel and revert it back to it's Alfine 8 glory. Current wheels are 29". I was thinking of only purchasing the rear wheel complete with hub...it is all I need. Tho, I am encouraged to buy a pair of wheels rather than just one rear as it is easier to sell a pair than just one rear wheel (the ones I would take off). The only thing is, that wheels available within my budget are both advertised as described below.

My Q - On the website the rear wheel with the Alfine 8 hub is described as 28" with dimensions of 622x19. And the front wheel is described as 29" with dimensions 622x19.

What is the difference? Dimensions are the same! Could I use these two wheels together with the same tyres I already have?

Some say 29"and 28" are the same just marketed differently for different bikes, others say they are different...what it is then?

Any help and clarification welcome!!!!!!!!!

  • Worth a read - sheldonbrown.com/tire-sizing.html 28" in this context is most likely a typo.
    – mattnz
    Mar 4, 2019 at 23:07
  • Consider that a 27" tire is bigger (on its inside diameter, at least) than a 29" tire. Tire sizes basically don't make sense. Mar 4, 2019 at 23:35

2 Answers 2


Inch measurements for wheels are really just labels that often refer to the diameter of the rim plus a nominally sized tire rather than an accurate measurement of the rim diameter.

The 622x19 spec is what you need to pay attention to. 622 is the diameter of the rim bead seat in mm. 19 is the inner width of the rim in mm.

Look at your tires, if they are marked 'ISO 622' or 'ETRTO 622' or '700C' (an French system label that is the same as ETRTO/ISO 622), then they are 622mm diameter.

You can measure the inner rim width of your rims. They don't have to be exactly 19 mm for your current tires to fit. A tire of a given overall width will fit on a range of rim widths.

  • 1
    To add a little context to this, the wheel size that is technically designated ETRTO 622 is sometimes referred to as 28" in Europe (where they don't even use inches) and 29" in the context of mountain bikes. As Argenti says, these sizes are the approximate outside diameter of the tire when used on a "roadster" or mountain bike, respectively. But yeah, wheel sizes are confusing. Read the Sheldown Brown article.
    – Adam Rice
    Mar 5, 2019 at 4:15

622x19 = 622x19

28" and 29" are just marketing.

  • 2
    The gist of your comment is that the ETRTO sizes are well defined and mean exactly what they say, whereas inch-based measurements have multiple definitions, and that any modern (post 1990) bike should be discussed using ETRTO sizes for accuracy.
    – Criggie
    Mar 5, 2019 at 3:18
  • indeed. well put. Mar 6, 2019 at 17:11

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.