Gravel bikes are designed for versatility, excelling on varied terrains from smooth pavement to loose gravel paths. A key component influencing a gravel bike’s performance across these surfaces is the tyres. Gravel tyres, characterized by their knobby or textured treads and supple construction, are engineered to provide grip and comfort off-road. However, a common question among gravel cyclists, especially those who also spend time on paved roads, is: are gravel tyres slow on road? This article delves into the performance of gravel tyres on tarmac, particularly focusing on the often-discussed topic of rolling resistance during road climbs.
It’s a common experience for riders transitioning from road-specific tyres to gravel tyres to notice a difference in effort, particularly when tackling hills on paved surfaces. While laboratory tests measuring rolling resistance on smooth drums might suggest a certain level of efficiency, real-world riding, especially on steep inclines, can tell a different story. The perceived sluggishness of gravel tyres on road climbs isn’t simply a matter of increased rolling resistance as traditionally measured; it’s also related to how these tyres deform under high torque and vertical load on hard, smooth surfaces.
The very features that make gravel tyres excel off-road – their supple casings and flexible knobs – can become a drawback on hard tarmac. Off-road, this suppleness allows the tyre to conform to uneven surfaces, maximizing grip and minimizing rolling resistance on loose terrain. However, on smooth, hard roads, especially when climbing steep hills and applying significant pedal force, this deformation translates into energy loss. The tyre essentially squishes and flexes along the direction of travel as well as under the rider’s weight, absorbing energy that would otherwise propel the bike forward. This effect is amplified on inclines where gravity further increases the load and the rider’s effort is already maximized.
To illustrate this point, consider a comparison with a tyre known for its robust construction and focus on puncture protection, like the Schwalbe Marathon Plus. Despite being considered a less performance-oriented tyre due to its stiffness, the Marathon Plus can feel more efficient than a gravel tyre on steep road climbs. This is because its stiffer construction resists deformation under load, minimizing energy loss on hard surfaces. On flat roads and descents, the difference might be less noticeable, but the uphill drag of gravel tyres on pavement becomes significantly more apparent.
For riders who frequently switch between road and gravel and don’t want the hassle of changing tyres or wheels, finding a compromise tyre is often the solution. Tyres like the Schwalbe G-One Overland, designed as a road-biased gravel tyre, aim to bridge this gap, offering a balance of off-road capability and on-road efficiency.
However, for cyclists who regularly ride in dedicated road groups or prioritize speed on pavement, the ideal solution might be to have separate wheelsets or even dedicated bikes – one optimized for road and another for gravel. While managing two bikes or wheelsets requires more investment and storage space, the performance benefits of using the right tyres for the right terrain can be significant, especially for riders who value efficiency and speed across diverse riding conditions. Ultimately, understanding how gravel tyre characteristics affect rolling resistance on different surfaces is crucial for making informed choices about tyre selection and bike setup.
