What are Drain Holes on bicycle wheels? Why should we drill the Drain Holes?

What are Drain Holes?

The drain holes are designed to allow accumulated water inside the bicycle rim to drain out. They are a practical feature that enhances the performance of the wheels and makes riding safer, especially in challenging riding conditions.

Why should we drill the Drain Holes?

As we known, in rainy or wet driving conditions, the rainwater will enter the inner cavity of the rim through the spoke holes. If the rainwater is not drained in time, the weight of the wheel increase, which will not only reduce the riding speed, but also increase the braking load. On the other hand, because the water flows inside the rim, if we change the riding speed while riding, the flowing water will affect the balance and stability of the wheel due to inertia factors, thereby increasing the possibility of danger.

Furthermore, the trapped water inside the rim may accelerate corrosion of the wheel rim, leading to premature wear and potential failure. Proper drainage reduces the risk of corrosion, helping to maintain the structural integrity of the wheel.

Therefore, to prevent the above situations from happening, we drill the drain holes on the rims to improve wheel performance, to enhance safety and to prolong the lifespan of your bike wheels. 

Some people may ask, will drilling drainage holes in the rim affect the strength of the rim? The answer is no. The diameter of the drainage holes is only 2mm, and only two are drilled on each rim, usually located at the three o'clock position on both sides of the rim, which has negligible effect on the performance of the rim.