Rim Width Explained: How Internal and External Widths Impact Your Ride

Rim Width Explained: How Internal and External Widths Impact Your Ride

The internal and external rim width plays an essential role in the overall performance and characteristics of a wheelset. The internal width is the distance between the bead hooks on either side of the rim, while the external width is the distance from the outermost edge of the rim to the opposite side. In this article, we'll take a closer look at the impact of rim width on your ride.

Wider Internal Rim Width for a Smoother Ride

A wider internal rim width allows for the use of wider tires, which can provide a smoother ride, better traction, and improved handling in corners. Wider rims also increase the volume of air in the tire, resulting in a more comfortable and compliant ride. Additionally, wider rims can improve aerodynamics by creating a smoother transition between the tire and the rim.

Wider Rims for Better Aerodynamics

The trend towards wider rims in the road bike industry is driven by several factors. One of the primary reasons is the desire for better aerodynamics. Wider rims create a smoother transition of air from the tire to the wheel, reducing turbulence and drag for a faster, more efficient ride. Additionally, wider rims allow for wider tires, which can provide better traction, comfort, and handling on various terrain. Wider rims can also offer better lateral stiffness, improving power transfer and handling precision. Finally, wider rims can provide a more comfortable ride due to the increased air volume within the tire, which can absorb more road vibration.

Reduced Drag for a More Efficient Ride

When the tire meets the rim, a small pocket of turbulent air forms at the rim's leading edge. This area of turbulent air creates drag, which reduces the wheel's overall efficiency. By increasing the rim width, the tire can sit more flush with the rim's sidewall, creating a smoother transition between the tire and the rim. This reduces the size of the turbulent pocket and the drag it creates, resulting in a faster and more efficient ride.

Wider Base for Improved Power Transfer and Stability

The wider rim provides a wider base for the tire, allowing for a greater contact patch between the tire and the ground. This increased contact patch reduces tire deformation, which translates to improved power transfer. When a tire is mounted on a wider rim, it can create a broader, more stable shape with a larger contact patch on the road relatively to a narrow rim. This can result in several benefits, such as improved traction, better cornering grip, and increased comfort due to lower tire pressures. The wider rim can also help to reduce rolling resistance by minimizing the tire's deformation as it rolls, resulting in a more efficient transfer of energy from the rider's legs to the road.

Wider Tires for Lower Rolling Resistance

A wider rim also gives the possibility to mount a wider tire. Wider tires generally have lower rolling resistance than narrower ones due to their ability to run at lower tire pressures while maintaining the same rolling resistance. This is because wider tires have a larger contact patch with the ground, which reduces the pressure at any given point and results in less deformation and hysteresis losses. In addition, wider tires often have a lower profile, which reduces the energy required to deflect the tire and reduces the overall rolling resistance

Finding the Optimal Tire Size

While wider tires can offer many benefits, there is a point at which they become too big or inefficient. Finding the optimal tire size for your bike and riding style involves balancing several factors, including aerodynamics, rolling resistance, comfort, handling, and weight. Here's a breakdown of recommended tire sizes based on different types of road cycling:

Road Racing: For road racing and criteriums, a tire size of around 25mm is typically recommended. These sizes provide low rolling resistance, excellent handling, and good aerodynamics. However, some riders may opt for 28mm tires in certain conditions, such as wet or rough roads, to improve traction and comfort.

Time Trials and Triathlons: In time trials and triathlons, aerodynamics is the primary concern. A tire size of 23mm be used to reduce drag and improve speed. Since the reduced frontal area of the narrower tire outweighs the rolling resistance at such high speeds.

Endurance Riding: For endurance riding, a wider tire with a size of 28mm or even 30mm is often recommended. These sizes provide improved comfort, lower rolling resistance, and better traction on varied terrain. The increased air volume of wider tires also helps to absorb road vibration, reducing fatigue and improving rider comfort over long distances.

Ultimately, the optimal tire size for your road bike will depend on your personal preferences and the type of riding you plan to do. It's important to consider factors like aerodynamics, rolling resistance, comfort, handling, and weight to choose a tire size that meets your specific needs. Experimenting with different tire sizes can also help you find the perfect balance of performance and comfort for your riding style.

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