Times are changing at a rapid pace. In our memories, the mainstream road wheelset width was always 19mm, and the tires were 23mm. We used to believe that narrower road tires meant higher tire pressure, resulting in faster speeds. However, wider tires provide more comfort and have lower rolling resistance at lower pressure. With the increasing popularity of tubeless tires on road bikes, low tire pressure has completely transformed the world of road bikes. The most significant change is that road bikes have become more versatile and can now comfortably traverse rocky roads. Aerodynamic road bikes can also be used for this purpose, while endurance road bikes can be lighter and more aerodynamic.
Mainstream road tires are now transitioning from 25mm to 28mm to match wider tires. Buying wheelsets smaller than 21mm inner width now seems outdated, with 23mm, 22mm, and 25mm inner widths becoming increasingly popular. This has resulted in road wheelsets being divided into two schools of thought: 21mm and 23mm inner widths. The question remains: What is the mainstream wheelset inner width?
From the perspective of international big-brand wheelsets, Roval, Vision, and Shimano are 21mm internal width schools, Bontrager, Enve, and Zipp are 23mm schools (the hookless wheelset also has 25mm internal width), and Campagnolo is changing from 21mm to 23mm. It's a 50/50 split between 21mm and 23mm internal widths.
From 19mm To 21mm: A Magical Transformation
To fully embrace tubeless tires, starting with a 21mm internal width is recommended. This is because wider internal width allows the tire to expand more and utilize lower pressures, which is the main advantage of tubeless tires. Additionally, it prevents the tire from bulging out and provides superior lateral support, which reduces the risk of the tire twisting sideways when using lower pressures.
From 21mm To 23mm: The Tires Are Wider!
When you increase the width of your wheel by 2mm, say from 21mm to 23mm, you're adding an extra 2mm. But this change isn't as significant as upgrading from 19mm to 21mm. There's no noticeable difference in the tire's lateral support between 21mm and 23mm. However, the increased internal width of 23mm allows the tire to expand by an additional 1-2mm, which means you can use lower tire pressure, around 5-10psi, for greater comfort without sacrificing roll resistance. For instance, if you mount Michelin POWER CUP 25c tires on a 21mm wheelset, they'll be 28mm wide. If you mount them on a 23mm wheelset, they'll be 1.4mm wider, that is, 29.4mm wide. This effect is equivalent to having wider tires without adding weight.
For those who prefer not to use tubeless tires, a 23mm inner-width wheelset is recommended. This is because the inner tube takes up some space, reducing the air capacity of an open tire with an inner tube compared to a tubeless tire. As a result, when using the same tire width and rider weight, the tire pressure needs to be increased by 5-10psi. The 23mm inner width wheelset can compensate for this drawback in most cases when compared to a 21mm wheelset, as the tire can expand wider. However, it still cannot be used with ultra-low tire pressure like tubeless tires, as it can cause a flat tire due to snakebite.
23mm Inside Width Is Better Suited For 28mm Tires
Not long ago, only endurance road bikes used 28mm tires. However, now 28mm has become a race road bike tire that is more comfortable than 25/26mm tires. Sometimes, comfort means speed. The 23mm inner width is better suited to fit 28 mm tires than the 21mm. Typically, the outer width of a wheelset with a 23mm inner width will be 30mm or wider. This is a more aerodynamic fit for 28mm tires.
Conclusion
The 21mm and 23mm wheelsets generally have similar inner widths. Both hooked 21mm and hookless 23mm wheelsets are suitable for tubeless tires, and there is little difference in their actual use. However, the 23mm inner width for open tires is better suited for lower tubeless tire pressure (21mm inner width), providing greater comfort. If you are a heavy rider looking to use 28mm or wider tires, the 23mm inner width is more beneficial.