Due to advancements in carbon fiber materials, the classification of road bike wheelset rim heights has significantly changed compared to traditional methods in recent years. This article will explain how disc brake road bike wheels are classified by rim height.

Under 30mm

Rims under 30mm are generally made of aluminum alloy. Because aluminum alloy wheels are heavy, to control wheel weight, many aluminum alloy wheel groups do not exceed 30mm in rim height.

Currently, high-end carbon fiber climbing-specific rim wheels under 30mm are very rare. Examples include Campy's Hyperon and Shimano's C24 tubular version. Unless you need extreme lightweighting or to tackle climbs steeper than 15%, few people opt for these 30mm or less carbon fiber wheels, as they are not cheap and don't look particularly stylish. For this reason, major brands have stopped producing carbon fiber wheelsets under 30mm.

30-35mm

Due to advancements in carbon fiber materials, even mid-height 30-35mm wheels can now achieve lightweighting. As a result, most mainstream manufacturers' climbing wheels are now in this height range. Examples include Roval Alpinist, Campagnolo WTO 33, ZIPP 202, and ICAN AERO35 disc brakes. In challenging mountain stages of major grand tours, drivers are often seen using wheel groups within this rim height range.

From personal experience, when climbing gentle slopes, 30-35mm rim height wheels certainly feel smoother than lower rim height wheels. Rim heights under 35mm primarily prioritize lightweighting, which enhances acceleration performance and responsiveness. However, their aerodynamic performance and inertia are not as good, which can be noticeable in high-speed sections.

35-50mm

Previously, 50mm wheels, with their high rim height and widespread use by many brands, offered the best all-around performance. They are now classified as mid-level rim height wheels. This is thanks to the progress in carbon fiber materials. Wheels in this height range offer the best all-around performance and are very suitable for hilly terrain. Furthermore, lightweight wheels with a moderate height are also suitable for climbing gentle slopes.

For wheels with moderate height, those under 42mm are biased towards climbing, such as the Aeolus 37 RSL, Bora 35, new Zipp 303, and ICAN AERO40 carbon wheels. Those over 42mm are biased towards flat roads, such as the CADEX 42, old Zipp 303, Aeolus XXX 4, and ICAN NOVA 45 carbon wheels. This is my personal opinion. Since I mostly ride on flat roads, I personally prefer 45mm height wheelsets.

However, aesthetically, I think 38-40mm wheels look more harmonious on competitive frames.

50-65mm

Wheelsets in this rim height range can largely be considered "flat road killers." The 55-60mm range is dominant. Examples include Vision Metron 55 SL, the famous ZIPP 404, CADEX 65, Roval CLX 64, and ICAN NOVA 55. As wheelsets in this height range are significantly affected by side winds, combining a lower height wheel at the front with a higher height wheel at the rear can reduce the impact of crosswinds. Examples include the Roval Rapide, and our own 40/50mm front/rear wheelset.

High rim height wheelsets are designed for high-speed cruising and are suitable for flat roads. If you can maintain speed, you'll feel the effort saving. However, if you don't reach the optimal operating speed, it can feel like a drag. Therefore, choosing a high rim height wheelset definitely requires significant power output.

65mm and above

Wheelsets over 60mm in height are rarely seen on road bikes and are primarily used for time trial bikes or chronographic races to maintain high-speed cruising stability. Examples include Zipp 808, BORA WTO 77, DT ARC 1100 80, Metron 81 SL, and ICAN AERO86 carbon wheels. Since they are solely designed for aerodynamic effect, ultra-high rim wheels are generally heavy and have a large surface area exposed to crosswinds, making them clearly susceptible to side winds and requiring high control skills for road bikes.

Disc Wheels

Disc wheelsets are designed for the ultimate aerodynamic effect. They are often seen in flat road time trials in road racing. Disc wheelsets are very heavy and demand extremely high user ability, significantly impacting climbing. This is evident in this year's Tour de France individual time trial, where most riders chose to switch to lighter road bikes for the climbing sections.