How to find the optimal tire pressure for carbon road wheelset?
Can inflating the tires of a road bike wheel achieve the best riding effect? This statement has become a thing of the past. Excessive tire pressure not only makes riders feel uncomfortable, but it has also been proven that cycling speed will decrease as a result. Therefore, choosing the appropriate road tire pressure is one of the simplest and most cost-effective ways to improve bicycle performance and comfort. Whether you are a beginner or an experienced cyclist who wants to optimize performance, this article can give you unexpected gains!
Finding balance is the key to finding the appropriate tire pressure. In order to minimize energy loss caused by tire deformation and provide predictable cornering control, your tire pressure should not be too low; But in order to provide cushioning and shock absorption, your tire pressure should not be too high.
This blog will be divided into three parts, providing a detailed explanation of why carbon bike wheel tire pressure is so important, which factors can affect finding the optimal tire pressure, and how to find the most suitable tire pressure for you.
Recommended tire pressure for carbon road bike wheels
Bola has placed approximately 65psi in his 28mm tires. Some tire manufacturers provide air pressure recommendations or calculators for their road bike tire series, which we can use as reference data for riding on sunny and flat asphalt roads. As we are preparing to discuss, you should pay close attention to the actual size of the tire when inflating, as this can change the optimal air pressure for any specific combination of wheels and tires. If the actual width of the inflatable tire is greater than the width on the label, the required tire pressure will be slightly lower than the recommended values in these tables, and vice versa. Meanwhile, for heavier cyclists or those carrying heavy loads on their bicycles, the optimal tire pressure should be higher, while for lighter cyclists, the optimal tire pressure should be lower. Finally, it is important to remember to comply with the pressure limits set by the wheel and tire manufacturers, especially the upper limit. These are usually printed on the sidewall of the tire or carbon wheel rim. If you have a set of carbon bike wheels without hooked rims, the maximum allowable tire pressure may also be lower than that of wheels with hooked rims. The following recommendations are for TLR tubeless road tires from Pirelli. No matter which brand of tires you are using, as long as you consider the various factors we will introduce later when adjusting tire pressure, these recommendations will be a good starting point. Perhaps the recommendations of other brands may differ, but here Pirelli suggests that drivers weighing over 96kg/212lb should use tires of 700 x 25c or larger, as for drivers of this weight, the recommended tire pressure will exceed the maximum allowable pressure of 700 x 23c tires. Similarly, it is crucial not to exceed the maximum air pressure indicated on the tire or wheel rim. What is the difference between Pirelli's suggested air pressure and the tire pressure I personally use? Let's take a look at some examples. Firstly, I would like to inform everyone that my weight is approximately 63 to 64 kilograms. Personal time trial is a form of competition that I personally really like. On Bola carbon fiber bike wheels, we use 23mm wide tires mounted on 19mm wide wheels, but their actual width after inflation is close to 25mm. Considering that most time trials are usually conducted on roads with good conditions and not too many potholes, we set the air pressure on the front and rear tires to approximately 90 psi. However, on the Bola 45mm carbon wheelset,we usually use 28mm tires on the 19mm wheels. For this, we usually use a pressure of about 65psi because I often ride on rough and uneven roads.
Are you riding a carbon MTB bike or a gravel bike?
The tire pressure applicable to carbon road bikes is vastly different from that of mountain bikes or gravel bikes. Getting the correct tire pressure on a road bike is very different from a carbon mountain bike or cabon fiber gravel bike, where the tires (and rims) are noticeably wider and the terrain is looser, and you have to deal with trail obstacles. If you are riding off-road, we have a separate guide for mountain tire pressure and gravel tire pressure here.
Key considerations
If your tire pressure is too low, you may press the tire against the wheel rim, causing a blowout or damage to the wheel. Generally speaking, the correct tire pressure will make your ride easier, more comfortable, and reduce the chance of a blowout. From a performance perspective, optimizing tire pressure is crucial for reducing rolling resistance and improving comfort. Rolling resistance refers to the force that prevents a tire from rolling on the ground. If your air pressure is too low, more kinetic energy will be lost during tire deformation and friction between the tire and the road surface. This will also increase the likelihood of tire blowouts. If your tire pressure is too high, the tires will become very hard, and your bicycle will be bumpy when passing through steep roads, which not only greatly reduces the comfort of riding, but also wastes energy.
Feeling fast may not necessarily be fast.
High tire pressure may give you the illusion of being fast, but the fact is not so. Once a certain critical value is exceeded, adding more air to the tire will actually reduce grip, increase high-frequency vibration, and lead to additional muscle fatigue. All of this will slow down your speed. Only by obtaining the correct tire pressure can one ride faster and more comfortably.
Inflating tool
Life is too short to survive without a pressure gauge. In order to set the appropriate tire pressure for your road car, it is best to have a floor standing pump with a built-in pressure gauge. It doesn't require a lot of money, but considering that you will use it for a long time, it's still reasonable to buy something of higher quality. If you want to fine tune your tire pressure, a good tire pressure gauge is also worth investing in.
Be careful
when it comes to road tire pressure, it is better to "lower" than "too high". According to Bola's testing, once the optimal air pressure set by regulations is exceeded, performance will rapidly decline. A slightly lower speed will only result in relatively small speed loss, but it should be noticeably more comfortable on rough and uneven roads.
Factors affecting optimal tire pressure
As mentioned in the tire pressure chart above, the recommended values can serve as a regular starting point. They will give you the correct approximate range, but in addition to tire and wheel size and cyclist weight, there are many factors that can affect your personal optimal road tire pressure.
width is important
When inflating a tire, accurately determining whether the tire size is wider or narrower than its nominal size based on the width of the inner rim of the installed wheel is the key to calculating the optimal tire pressure. Although most bicycle tires are labeled with specific sizes, such as 700 x 25c, the actual inflated size of any tire will depend on the tire design and the inner rim width of the carbon bike wheel. The carbon rims internal width of most new road tires is about 19mm. As shown in the figure, carbon wheels with wider inner rim widths may increase the measured width of the tire when inflated. Most new tires are now designed around the latest 2020 ETRTO (European Organization for Tire and Wheel Technology) standard, with an inner width of 19mm. Therefore, when inflated to the specified pressure, wheels with inner rim widths wider than this may increase the measured width of the tire (and vice versa). Therefore, the optimal air pressure may be lower than when using the same tires on narrower wheels. Riding a lightweight and fast road bike? Assuming all other variables are the same, your tire pressure needs to be lower than that of a heavy-duty bicycle, even though the rider makes up the vast majority of the system weight - as we have discussed, heavier riders typically require higher tire pressure than lightweight riders - but remember to include your bicycle weight and the weight of the equipment you carry with you. If you are riding a lightweight optimized road bike weighing less than 4 kilograms and do not carry heavy equipment, you may need to lower the tire pressure by a few psi. vice versa. If you are riding a heavy heavy-duty bicycle or a road bike with luggage, you may need to inflate your tires more. For road bikes, the weight of the rider is usually not evenly distributed between the two wheels. The exact proportion of each cyclist may vary depending on their riding position and bicycle style, but typically the rear wheels bear more weight than the front wheels. Generally speaking, it is not a problem for the front wheels to have a few psi less than the rear wheels.
Trail conditions
The road conditions during cycling affect the ideal tire pressure. If you ride on a very smooth trail, the higher the tire pressure, the faster the speed. However, on steep surfaces such as roads, excessive pressure will only increase vibration and force you to slow down. The more rugged and bumpy the road is, the lower the ideal tire pressure will be. When the road becomes very rough and uneven, narrower tires (25mm or narrower) running at relatively low air pressure may not provide sufficient protection for the wheels or inner tubes - especially for heavier riders - and may even cause tire blowouts or wheel damage. If you ride on rough roads or gravel, reducing tire pressure can help improve comfort and reduce the possibility of tire blowouts. Switching to larger tires will give you more tire capacity to adjust tire pressure to balance rolling resistance and comfort on rough roads. That's why professional athletes choose to use tires larger than 28mm on cobblestone tracks, such as the Flanders and Paris Rube tracks.
Weather and Temperature
Reducing tire pressure in wet conditions may give you more grip. When the road surface is slippery or it looks like it may rain during cycling, you can reduce the pressure on both tires by about 5psi. This helps to increase the amount of rubber in contact with the road surface, thereby improving grip. Whether it is the environment or the high temperature caused by wheel braking, it will increase tire pressure. If you are going to ride a bicycle with ring brakes (especially one with carbon rivet wheels or latex inner tubes) down a long slope in the hot summer, be careful not to over inflate your bicycle tires. Because if too much heat enters the system, it can cause dangerous high pressure inside the inner tube or tubeless tire.
Tire structure
The material and construction of tires also affect the optimal tire pressure. The materials and construction methods used by road bicycle tire manufacturers also have a small impact on the optimal tire pressure. Road car tires designed for racing or summer use often have a carcass that uses more and finer nylon or cotton threads (referring to the number of threads per inch or TPI of the tire), with only a thin layer of rubber tread at the top. This makes them more prone to deformation under pressure, making cycling smoother and faster. On the contrary, winter road bicycle tires typically have harder and more durable outer tires with fewer and thicker nylon threads. The top rubber tread is often thicker to improve mileage and puncture protection. Given this, when replacing with winter tires, you may need to slightly lower the road tire pressure, as the optimal pressure for comfort and grip may be a few psi lower.
Tubeless tire
Tubeless tires eliminate the risk of air leakage. If you use tubeless tires, remember that having no inner tubes means you can safely operate at lower pressures and there is no risk of flattening the inner tubes. Lower tire pressure can improve off-road grip. If you are riding a road bike with relatively large tires and want to do some simple off-road or gravel riding, tubeless tires will be very useful.
Why do tires lose pressure?
Before each ride, make sure to check your pneumatic tires. The main reason for the gradual deflation over time is due to gas permeation. This refers to the escape of air through the tire structure, which is only a result of material properties. Therefore, it is important to check the tire pressure before riding. Once the desired air pressure value is determined, simply inflate the tires regularly to the desired level. If you don't ride your bike for a period of time (such as the entire winter), we recommend hanging it off the ground. This can prevent the inner tube from aging and damaging due to contact with the ground when the tire is completely deflated. Alternatively, remember to inflate the tires to the appropriate level from time to time.
Fine tune road tire pressure
No one likes to be trapped on the roadside repairing tires. You now have all the relevant information, but how can you specifically fine tune tire pressure? Simple answer: Through experimentation. Firstly, start with the recommended values above, and then consider the road conditions of your cycling route. If most of the road sections you ride on are newly laid flat asphalt pavement, then the recommended air pressure values mentioned above may already be close to optimal. If your situation is not like this,you can start with the recommended values above and gradually reduce the air pressure during each ride to conduct the experiment. Starting with a small adjustment of approximately 5psi (pounds per square inch), if you pay close attention, you should eventually be able to find the optimal balance between speed and comfort. You need to find a pressure value that makes you feel stable, so that you don't feel like the tires are collapsing under you when cornering. Furthermore, as mentioned earlier, it is a principle worth remembering that it is better to be slightly lower than too high.
Field testing
If you are serious, you can use a power meter to conduct some basic field tests to try to find your optimal tire pressure, or if you have an accurate and reliable power meter, you can do some basic field tests yourself. Find a long and stable uphill section with an average slope of over 5%, and then see how different tire pressures affect the power you need at a certain speed, or the speed you can achieve at a fixed power output. The data you have obtained should help you find the optimal tire pressure for the settings and road conditions used during testing. What you are looking for is the minimum power required at a fixed speed, or the tire pressure that can achieve the fastest speed at a fixed power. Just like any test, it is very important to keep all other variables (such as system weight, riding posture, traffic conditions, weather, etc.) the same in each test, otherwise the results will become inaccurate.
Find the most suitable tire
We have learned that different tires will perform differently, and with time and continuous experimentation, you will learn which tires are most suitable for your preferred riding style.