What’s the optimal tire width for road bikes? We tested 26mm and 30mm tires to find out.
The choice of tire width has always been one of the most hotly debated topics in road cycling. Traditionally, narrower tires (23mm or smaller) have been used because they are generally lighter and therefore perceived as faster. However, recent trends have been moving in the opposite direction. Manufacturers are encouraging cyclists to use wider tires (28mm or larger), claiming they offer lower rolling resistance and a more comfortable ride.

But what tire width is best for road cycling? Tire widths can’t go infinitely wider, so to answer this question, the authors designed two tests, both using Pirelli P-Zero Race TLR tires in two different sizes: 700×26mm and 700×30mm. The 26mm size was used to represent a standard, narrower tire width, while the 30mm size was used to represent a width considered quite wide for road bikes. The first test was conducted indoors on a roller trainer, while the second was conducted outdoors on a track with a variety of road conditions for better validation. While indoor testing should provide some reliable data on the rolling resistance differences between narrow and wide tires, it’s also crucial to evaluate the compatibility of each tire set in real-world conditions. Ultimately, rolling resistance is ultimately determined by the road conditions.

In our experience, when it comes to road tire width, there’s a balance to be struck between comfort, rolling resistance, and aerodynamics. For example, wider tires may be more comfortable, but using them may mean sacrificing a small aerodynamic advantage. While the exact balance depends on your bike and riding style, I’ll provide some suggestions to suit your needs.

Indoor Roller Trainer Testing
Due to the many variables at play outdoors, such as wind and frequent starts, conducting real-world data testing may not be the best option. Riding indoors on an indoor roller trainer provides a more controlled environment, allowing for better testing of specific variables.

Indoor Roller Trainer Testing Part 1: Tire Width
The test is straightforward. Two sets of tires of different widths are taken and ridden on rollers at a fixed speed for fixed intervals. The power required to maintain this speed is then recorded. Everything else—the bike, wheels, riding position, etc.—remains constant, and the tire pressure is the same each time: both the 26mm and 30mm tires are inflated to 90 psi. If one width is faster than the other, it should require a lower power output to maintain the target speed. We can then infer that this width produces less rolling resistance.

In this test, the target speed was 40 km/h, and the intervals were 5 minutes. Before each test interval, I performed a 5-minute warm-up at an average speed of 10 km/h to bring all system elements to a consistent operating temperature. Each test was repeated twice, and the average was taken to ensure consistency.

It is important to acknowledge that this test does not fully replicate real-world riding, as the roller surface is much smoother than any road. The tire also deforms slightly differently on the roller compared to pavement, as the smaller diameter of the roller magnifies this deformation. However, it still provides a proven method for controlling test variables.

All testing was conducted on an ICAN Carbon Road FL1 road bike equipped with a UCI Lightweight Carbon Disc Gravel/Road wheelset (40C-UL). As previously mentioned, the tires used for testing were Pirelli P-Zero Race TLR tires in sizes of 700×26mm and 700×30mm. The tire construction and rubber were identical, with the only difference being the tire width. Although these tires are tubeless-ready, they were tested with butyl innertubes for ease of tire replacement. This resulted in a slight increase in rolling resistance compared to tubeless, but the difference between the two wheels was not noticeable. Power was recorded using a set of power pedals, calibrated at the start of the test.

Conclusion

Cycling at 40 km/h on a roller trainer with a 30mm tire requires an average power output of 152 watts, while riding at 40 km/h with a 26mm tire requires an average power output of 166 watts, a difference of 14 watts. Ignoring aerodynamics, and applying the same pressure on a completely smooth surface, wider tires will be significantly faster than narrower ones.

This is because, at the same pressure, wider tires have higher wall tension and a shorter, wider contact patch. The first factor means less energy is lost to tire bending, while the second factor reduces rolling resistance because the shorter, wider contact patch reduces frictional losses.
This test misses a key point: in real-world riding, tire pressure comes into play.

Indoor Roller Trainer Test Part 2: Tire Width and Pressure
When using wider tires in the real world, we typically don’t inflate them to the same pressure as narrower tires. Doing so results in higher tension in the wider tire, making it stiffer and more uncomfortable than the narrower tire. A 30mm tire inflated to 90 psi is, as you can imagine, quite stiff. One of the benefits of using wider tires is that they are supposed to be more comfortable, but if the tire pressure is too high then we can’t reap that benefit in the real world.

On very smooth surfaces like rollers or a track, higher tire pressure and tension reduce rolling resistance because less energy is lost through deformation and the contact patch is reduced. However, in the real world, where roads aren’t as smooth, wider tires require lower pressures than narrower ones because we want the tire casing to deform and absorb road vibrations. If we overinflate the tires, the bike will ride over these road imperfections, ultimately reducing grip and speed.

Therefore, in the second part of the roller test, we adjust tire pressures based on tire size. This means lower pressures for wider tires and higher pressures for narrower tires. This not only more accurately reflects real-world use but also offsets the rolling resistance advantage of the increased tension on wider tires.

According to Pirelli’s recommendations, at a weight of approximately 64 kg, I should run 26mm tires at 83 psi and 30mm tires at 65 psi, which are the pressures we tested in this part of the test.

Conclusion

At the recommended pressure, using a 30mm tire requires an average power output of 170 watts, while using a 26mm tire requires an average power output of 165 watts. Now the tables have turned, and on a completely smooth surface, without considering aerodynamics, the 26mm tire has a 5-watt advantage.
So why do narrow tires suddenly produce less rolling resistance than wider tires? Again, it has to do with deformation tension and tire pressure. A 26mm tire inflated to 83 psi deflects significantly less, and therefore has less contact with the roller, than a 30mm tire at 65 psi. This also means that the 30mm tire compresses more under the weight of the bike and my body, increasing deformation losses and increasing the size of the contact patch. If we precisely adjust the tire pressure for each tire size to produce the exact same deformation tension, or stiffness, rolling resistance would likely be the same.

Roller Test Conclusion
In conclusion, our roller tests show that, at the same tire pressure, wider tires do produce less rolling resistance than narrower tires. However, once we adjust the tire pressures for real-world riding, this advantage disappears. Real-world riding is important because it’s how we use our bikes, so choosing the optimal tire width still requires careful consideration.

What about riding on real roads?
Most people tend to ride on real roads, so obviously, a roller test doesn’t tell the whole story. While the roller test might not ultimately show a significant difference, experience tells us that wider tires can improve comfort and reduce kinetic energy loss caused by aerodynamics on rough surfaces.

Vibration Absorption and Control
On real roads, road tires need to act as shock absorbers, absorbing vibrations from the road rather than bouncing them around. This helps maintain speed and provides comfort and grip. To achieve this, tire pressure should be reduced as the road becomes rougher. However, on very rough surfaces, a tire that is too narrow may not have enough volume to absorb large bumps and is more likely to bottom out on the rim. For example, if you hit a pothole, the tire can be crushed between the rim and the obstacle, potentially causing a blowout and damaging both the tire and rim.

This problem is exacerbated for heavier riders and bikes, as they exert greater downward pressure on the tire. With this in mind, Pirelli recommends, for example, that riders weighing over 96 kg (or a combined rider and bike weight of that size) avoid using tires smaller than 700 x 25 mm.

Aerodynamics
On the other hand, on good roads where vibration damping is less critical, narrower tires may offer a small aerodynamic advantage by slightly reducing the frontal area exposed to the wind. Many modern aero road bikes and wheels are designed to achieve the lowest drag with a 25 mm tire. As a rule of thumb, you generally want the outer width of the rim to be slightly wider than the tire. However, this may only be a consideration for those competing in time trials or road races on good roads.

Overall, the trick is to find a tire that provides the right balance of vibration damping, grip, and aerodynamics for you. If you’re riding slower on rough roads, vibration damping and grip are priorities, which means choosing a wider tire. On the other hand, if you’re riding at high speeds on smooth surfaces, the slight aerodynamic advantage of a narrower tire may be worthwhile.

Real-World Impressions
While roller data indicates rolling resistance differences between tires under controlled conditions, for most people, it’s performance on real roads that matters most. To gather more subjective impressions, we also tested both tire models on a 2.7km loop south of Bristol, which features a variety of surfaces. This loop cleverly combines a freshly paved climb, a typical “normal” British road, an imperfect descent, and a short, flat, almost completely broken road in between.
For this test, I used tire pressures consistent with Pirelli’s recommendations: 83psi for the 26mm tire and 65psi for the 30mm tire for my weight. While we could attempt to gather some data by measuring the time we spent riding at a set average power, this test was conducted on open roads, making it difficult to eliminate the influence of rider and environmental variables. For example, wind speed, traffic, and individual variations in braking and line selection can all distort the data and introduce significant errors.

Thus, the purpose of this test was not to gather data, but to get a feel for how each tire width performs in the real world.

Real-World Riding Conclusions
As expected, the difference between the two tire widths was minimal on smooth tarmac. On good roads, the increased tire volume of the wider 700×30mm tire compared to the 700×26mm tire had no noticeable effect on comfort, but we do know there was a small aerodynamic penalty.

Once the road got rougher, the comfort and grip benefits of the wider tire became very apparent. Even on “normal” UK roads, the wider tire was noticeably more comfortable. Furthermore, the extra grip of the wider tire was a confidence-boosting experience once the surface got rough. This was especially true on descents, where the wider tire gave a greater sense of stability.

It’s important to note that while narrow tires may feel fast on rough roads, the high-frequency vibrations we experienced were quite unpleasant. As discussed in our tire pressure guide, wider tires at lower pressures can help keep the tire in contact with the road more often, thereby reducing rolling resistance.

So how do you achieve lower rolling resistance?

This is a complex topic, but the rolling resistance a tire produces depends largely on its construction and rubber compound. Generally speaking, lighter tires with thinner, softer rubber are usually faster than heavier, thicker, more rigid tires with features like puncture protection—you can experience the difference between summer and winter tires. As you might guess, road tires are almost always a trade-off between speed and durability. The best choice depends on your riding style. Paper-thin, lightweight tires are suitable for time trials on perfect roads, but may not be suitable for unplanned jaunts or long rides on local gravel trails.

What tire width should you use?

Roller tests show that at the same pressure, wider tires exhibit a rolling resistance advantage over narrower ones. However, this advantage disappears once you’re out in the real world. In the real world, the answer to the question, “Are wider tires faster?” is more nuanced. While wider tires don’t produce less rolling resistance than narrower ones, once you normalize tire tension, they shouldn’t roll slower either. Wider tires may also be more comfortable and offer better grip. A more comfortable and confidence-inspiring bike may also be faster overall, depending on the terrain.

Thus, tire width can be chosen based on other criteria, such as damping requirements, grip, and aerodynamics. Ultimately, you need to weigh what you want to achieve with your bike setup.

If your bike has enough clearance, we generally recommend a 28mm tire, a compromise that strikes a balance between all of these characteristics.

If you race on fine roads or time trials, a slightly narrower 25mm tire may offer a slight aerodynamic advantage at high speeds. However, if you race on rougher roads, a slightly wider tire may be better.

If you frequently ride on particularly rough surfaces or want to access some gravel sections, a 30mm (or larger) tire may offer greater comfort, grip, and handling, without compromising rolling resistance.