Which depth of road bike rim should I choose? This is a frequently asked question by new buyers.
Generally, rim depth is a trade-off between weight and speed.
- Shallow Rims (22-39mm) are lighter, easier for climbing and handling.
- Middle Rims (40-59mm) are relatively all-round, not too heavy for climbing, while still fast on flat road.
- Deep Rims (60mm+) are heavier, laboursome for climbing, but faster on flat road.
However, there are more elements should be taken into consideration in order to choose more suitable rims for you.
* Stiffness – comfortability or efficiency?
Rim depth is a key factor that affect the stiffness of carbon road bike wheels.
Generally, deeper rims are stiffer and of higher efficiency of power transmission since less power disperses from wheel flex.
Shallow rims provide better comfortability on rough roads since more bump and vibration are dispersed.
* Speed – light or aero?
Though shallow rim is lighter, it does not necessarily be faster. Aerodynamics and inertia should also be taken into account.
For two wheels with same weight, the one has higher weight percentage at the rim (compared to hub) is more likely makes you faster.
Lighter weight enables you accelerate faster at the early stage, but has less inertia for cruise.
Though heavier, deeper rims are more aerodynamic and provide better inertia during cruise stage.
In road racing, more riders prefer deeper rims which provide better aerodynamic and are relatively faster, considering better inertia is gained during cruise.
* Which depth to choose?
As mentioned above, rim depth is a trade-off between weight and speed.
Choosing the suitable rim depth means you need to consider which factor is more important for you for specific riding.
In time trial or triathlon racing, 88mm deep carbon rims or even 3-spoke wheel, 5-spoke wheel, and full disc carbon wheel are widely used, as such racings most take place on flat road condition.
If you will mainly use the wheel in hilly roads which require many climbing, shallow rims would be better option.
To sum up, the following things should be considered when choosing the depth of road rims:
- The main terrain to use (hilly or flat roads)
- The main usage for specific wheel (casual riding or racing)
- Rider’s weight, skill and style
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