There is a huge amount of debate around how to get the perfect bicycle tire pressure. Optimum pressure varies due to a number of factors and because of this there are no fixed rules. Keep in mind, the same physics and factors that apply to regular bicycles also apply to electric bikes and there are certain guidelines that you can follow to get approximately the correct pressure for an electric bike wheel. From there you can make adjustments to fine tune it.
Physics tells us that more pressure will allow a bicycle to roll faster because the tire will deform less and have a smaller footprint on the road, both of which lead to less rolling resistance. While this is true, it is only true on a perfectly smooth road. Unfortunately, the reality is that road surfaces vary greatly and they are rarely smooth at all.
Studies have found that decreasing pressure can actually increase speed as small bumps are absorbed by the tire instead of reaching the bike. Perception of speed is increased with higher pressure because more vibrations reach the rider, making him feel like he is moving faster.
The effect is easy to understand if you have ever ridden a mountain bike with tires pumped up hard. Every bump on the trail is transferred to the rider. While a hard tire has a smaller footprint and will indeed accelerate faster, mountain bikers need a lower pressure so that the bigger tire footprint can conform to the trail and give more grip, especially when cornering.
Although there is no one ideal tire pressure, you can get close to what you need by considering the following factors and steps below:
More weight pushing down on the tires will compress the air inside more. The more that the rider and bicycle weigh, the more pressure is needed to counter the effect of this compression. If you are a petite rider, then you will need a much lower pressure in comparison to a larger cyclist.
Road cyclists need the highest tire pressure. Trekking cyclists or “bike packers” riding on fire roads (also called “bikepacking” and is similar to backpacking but with a bicycle) will need a lower tire pressure and mountain bikers even less. A rough road surface will require road cyclists to use a lower pressure to avoid vibrations causing hand fatigue. Likewise, when riding off road, a higher pressure is more suitable to hard pack surfaces than loose sand or loam, which require lower pressures. Too low a tire pressure can cause snakebite punctures when riding off road, so don’t go too low.
If any surface is wet, tires will need a lower pressure to increase their footprint and grip. This applies to road and off road cycling. Too high of a tire pressure is often the primary cause for crashing when road conditions are wet.
Tire Volume and Rim Width
As tire volume increases, lower pressure will be needed to get the same ride feel. The same applies to rim width. Mountain bike rims have become wider in the last few years. A wider rim allows a tire to have a greater surface volume, which grips the road better.
How to Get the Correct Tire Pressure
- The minimum and maximum pressure should be visible on the side of the tire. Although this is a guideline, you should not exceed the maximum. Refer to the manufacturer’s website for an approximate pressure according to your body weight and use this as a starting point. Make adjustments according to the above considerations.
- Get a small portable pressure gauge and inflate your tires to the correct pressure on longer rides or regular commutes.
- Go for a ride. Take a pump and your pressure gauge with you. If you are riding on the road and notice lots of vibration, release 5 psi of pressure and try again. If you are riding off road and notice your tires bouncing off stones and roots, you should also release 5 psi. On the other hand, if you notice that your rim is hitting objects as you ride over them, you have far too little pressure in your tires.
- Experiment with different pressures. If you use a GPS tracker, you can see how different tire pressure affects your speed. You can ride a short section of trail many times. Start with a low pressure and add 5 psi each time until the tire starts bouncing off objects. Where did it feel best? Which pressure gave you the best grip in the corners? How does this change with different surfaces?
While there is no perfect tire pressure, it is certainly worth taking the time to play around with it and find what pressure works best for you and your style of riding. Bear in mind that as soon as you are riding on a different road surface or different kind of soil, the pressure you need will change. The same is true if it starts raining during a ride. The more you experiment with tire pressure, the more accurately you will be able to judge which pressure is right for you in every scenario.
At the end of the day, it costs nothing to inflate your tires a bit more or let out some air, so get out there and find the pressure that works best for you!
John T Lyons is the LEED guest contributor for this article. He grew up riding the canyons of San Diego on his single speed Huffy. After a stint working for Shelby American in automotive and then in the Aerospace industry, JT started Moment Bicycles. He developed a “better way to buy a bike” using his engineering problem-solving skills. Learn more at http://momentbicycles.com