What variables are considered when determining wheel size from a theoratical perspective and how do they affect these variables?

I noticed that city bikes tend to have smaller wheel sizes, whereas sometimes I see very large mountainbike wheels.

  • You you mean diameter of the tire? Wheel is the metal (or carbon) part?
    – paparazzo
    Mar 25, 2015 at 12:43
  • @Blam I do mean wheel size. Although I'm talking about bicycle wheels, this answer can also be interpreted to be more general, refering to "wheels". Mar 25, 2015 at 13:50
  • Then I don't get the very "large mountainbike wheels". Can you give an example of a very large mountainbike wheels. Pretty much all mountain bikes have 29 (ISO 622). The standard size for full size city bikes 700 (ISO 622). City bike 'tend' to have that size. Can you give an example of a city bike with smaller wheels? 700 and 29 is the same size.
    – paparazzo
    Mar 25, 2015 at 13:55
  • @Blam I guess I'm reffering to the 29" wheels. When I talk about city bikes, I'm reffering those foldable bikes with wheel sizes appearing to be have of those 29" ones (subjectively judged without measuring). Mar 25, 2015 at 14:01

1 Answer 1

  • The first variable is the size itself. When talking about folding city bikes, they have to be as compact as possible so you can take them as normal luggage when folded.
  • There's also the aspect of weight - smaller wheels are lighter but also have lower rotational inertia. This means they are easier to accelerate but once they gained speed, they don't hold it for quite as long as large wheels.
  • In mountain bikes the wheel size is a very individual thing. Smaller wheels offer better acceleration an better maneuverability (such bike is generally shorter and of course requires less force to turn a wheel). On the other hand, large wheels give better angle of attack meaning it's easier to roll over any terrain obstacles. Also, on a larger wheel you can have larger contact patch giving better grip.
  • There's also a question of stiffness, Small wheels, especially in cheaper ranges are stiffer because of shorter spokes used.
  • In most disciplines of cycling the wheel diameter is 550-650mm (not too precisely), so the differences are not enormous. Smaller wheels are used in folding bikes and BMXes - in the latter because of easier handling of a sherter, lower bike both on the ground and in the air.
  • I've partly mentioned the changes in bike geometry, but I'd like to make it clear - wheel size can affect your position on a bike. In particular when really large diameter wheels are used, handlebars will be up pretty high and there's little you can do about it with manipulating the frame geometry.

There's no single standard of wheel size for any bike types, which shows that manufacturers change their approach and priorities over time. It's also hard to determine the perfect wheel size for each person (talking about MTBs here), because it depends on people's personal preferences, experience and use of the bike.

  • I would say that for the most part, 700 (ISO 622) is "the standard" for road race bikes. You'll very rarely see 650 (ISO 571) tires on the smallest of road bike frames, but very few manufactures offer this, even on women specific frames. Basically every road (race style) bike will use 700c tires. 650 is more common in time trials and triathlons, but I would qualify that as a different kind of bike.
    – Kibbee
    Mar 25, 2015 at 12:44
  • That being said, the outer diameter for a 26" mtb and a 700c road bike with a tire on is pretty close typically when in the same application (commuting, for example)
    – Batman
    Mar 25, 2015 at 12:52
  • @Slovakov Is it correct to deduce the following variables from your answer: size and wight. With these two I can deduce the following outputs: 1. Ability to handle, when not moving (smaller and lighter is easier) 2. Ability to accelerate 3. Maneuverability 4. Ability to handle terrain 5. Campability for contact patch size (larger wheels allow for larger tire profile on the ground?!) 6. Stiffness 7. Affect on range of possible frame geometry. Spontaneously I would add 8. Price, bigger tending to be more expensive?! Mar 25, 2015 at 13:59
  • @Kibbee I agree that 700c is most common one, but I didn't want to mention it as standard having in mind 650c... and some very old standards like 27" (630 as I remember).
    – Slovakov
    Mar 25, 2015 at 18:47
  • @supercuteboy Yes, I'd say it's correct, maybe except foor point 8. I mean it's not always the case that bigger = more expensive. It depends on how popular a given size is. The larger number of prodcts, the cheaper they get.
    – Slovakov
    Mar 25, 2015 at 18:48

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