Times are changing rapidly. As we remember it, mainstream road wheelsets were always 19mm wide, and tires were 23mm. It used to be believed that narrower road tires meant higher tire pressure, which in turn led to faster speeds. However, wider tires are more comfortable at lower pressures, and also have lower rolling resistance at lower pressures. With the increasing popularity of tubeless tires on road bikes, lower tire pressures have completely changed the world of road cycling. The most significant change is that road bikes have become more versatile and can now comfortably navigate rocky roads. Highly aerodynamic road bikes can also be used for this, while endurance road bikes can be lighter and more aerodynamic.

Mainstream road tires are now moving from 25mm to 28mm to accommodate wider tires. Buying a wheelset smaller than 21mm internal width feels outdated, and 22mm, 23mm, and 25mm internal widths are becoming increasingly popular. This has divided road wheelsets into two schools of thought: 21mm and 23mm internal widths. The question remains: what is the mainstream internal width for wheelsets?

From the perspective of major international brands, Roval, Vision, and Shimano are proponents of 21mm internal widths, while Bontrager, Enve, and Zipp are proponents of 23mm (with hookless wheelsets also having a 25mm internal width), and Campagnolo is changing from 21mm to 23mm. The ratio of 21mm to 23mm internal widths is 50/50.

From 19mm to 21mm

To fully embrace tubeless tires, starting with a 21mm internal width is recommended. This is because a wider internal width allows for more tire volume and the use of lower pressures, which is the main advantage of tubeless tires. Additionally, it helps prevent tire bulging and provides lateral support for the tire when using lower pressures, reducing the risk of the tire twisting sideways.

From 21mm to 23mm: Wider tires!

If you increase the wheel width by 2mm, for example from 21mm to 23mm, you get an additional 2mm. However, this is not as significant a change as upgrading from 19mm to 21mm. Between 21mm and 23mm, there isn't a clear difference in the tire's lateral support. However, the increased 23mm internal width allows the tire to expand an additional 1-2mm. This allows for the use of lower tire pressures (approximately 5-10psi) without compromising comfort. For example, a Michelin POWER CUP 25c tire mounted on a 21mm wheelset will be 28mm wide. Mounted on a 23mm wheelset, it will be 1.4mm wider, meaning 29.4mm. This effect is equivalent to having a wider tire without increasing weight.

For those who do not want to use tubeless tires, a 23mm internal width wheelset is recommended. This is because the inner tube takes up some space, reducing the internal volume compared to a tubeless tire. As a result, when using the same tire width and rider weight, you need to increase tire pressure by 5-10psi. A 23mm internal width wheelset can usually compensate for this drawback because the tire will be wider. However, it cannot be used with ultra-low tire pressures like tubeless tires, as that could cause pinch flats.

23mm internal width is best for 28mm tires.

Soon, only endurance road bikes used 28mm tires. However, now 28mm is a comfortable race road bike tire, more so than 25/26mm tires. Sometimes, comfort means speed. A 23mm internal width is more suitable for 28mm tires than 21mm. Typically, a wheelset with a 23mm internal width will have an external width of 30mm or more. This is a more aerodynamic fit for 28mm tires.

Summary

Generally, 21mm and 23mm wheelsets have similar internal widths. Both hooked 21mm and hookless 23mm wheelsets are suitable for tubeless tires, with little difference in actual use. However, for open tires, a 23mm internal width is better suited for lower tubeless tire pressures (21mm internal width), offering a more comfortable ride. If you are a heavier rider using 28mm or wider tires, a 23mm internal width will be more beneficial.