Let’s Discuss The Science Behind Bicycle Tire Pressure

Maintaining the right pressure in bicycle tires not only increases the speed but improves comfort, grip, and puncture resistance as well. In contrast to popular belief, pumping the tires to maximum pressure is not an ideal practice. It may work for some riders but for most, it will make the ride uncomfortable and prone the tires to punctures.

In a nutshell, having the right bicycle tire pressure is the cheapest and simplest way to improve bike performance. In this piece, we will address some of the things that riders should take into account while pumping up the tire.

So, let’s dive right into it.

Tire Pressure & Its Role In Traction

Pneumatic tires were designed to improve the bone-jarring ride on the solid wheels. The air inside the tires acts as a cushion which not only provides comfort but also improves the grip and traction. Compressibility of air lets the tire conform to the terrain instead of transferring the impact force up in the frame. Consequently, riders do not have to experience jolts that are otherwise common with solid wheels.

That said, pneumatic tires can provide comfort and traction only when air pressure is optimal. Running the tire on either too low or high pressure can be potentially dangerous and have a negative impact on the handling of the bike.

Having too low pressure in the tires can cause excessive flexing in the sidewall which produces cracks and makes tires fragile. This can eventually blow the tire which can result in accidents.

Furthermore, low pressure makes tires prone to punctures and also allows them to roll off the rims. Consequently, the rims would start to bend and you would have to replace the entire wheel which is quite expensive.

Too high pressure also has similar implications. It can blow up the tire as well and squeeze the rim which would eventually require a replacement.

Moving on, tire pressure also plays a crucial role in handling a bike. With the low pressure, the bike feels slow, sluggish, and difficult to control. Whereas with the high pressure, riders would experience reduced grips and a bumpy ride which leads to fatigue and back pain.  

Recommended Pressure For Bicycles

Almost all bikes have recommended pressure printed on them. Usually, a range is written i.e., 95-120 psi but there are reasons, which we will get to shortly, to choose a figure between the range. That said, if your bicycle does not indicate a particular range, the general rule of thumb is as follows:

Factors That Determine Optimal Tire Pressure

Several factors are at play when it comes to determining the right pressure for the tires. Type of bike, size of tires and rims, rider weight, and terrain collectively dictate the optimal pressure. Let’s take a detailed look at them.

1. Type of Bikes

Bikes designed for different terrains require a varying degree of traction. Mountain bikes require better ground grip as they are built for bumpy and rough terrains. Pumping such bikes to high pressure would produce jolts and compromise the grip which can be dangerous on mountainous terrains. Hence, these bikes should be pumped at low pressure to improve shock absorption.

Most manufacturers recommend 30-50 PSI for such tires. You can pump it up to 30 for off-roading and 50 for on-road rides.

Road bikes are built for speed on plain and smooth roads. Riders generally do not have to encounter bumps on roads which reduces the “suspension role” of the tires.

Thus, riders can pump them up to 80 to 130 psi for a faster ride. Furthermore, the wheels of such tires are usually narrow and need higher pressure to keep them away from rims. Low pressure would not only slow the bike down but also make it more prone to punctures.

Hybrid bikes fall somewhere in between the road and mountain bikes and so does their air pressure. The recommended range for such bikes is between 50-and 70 Psi. And again, the exact figure would largely be dictated by the terrain and the speed riders expect from the bike.

2. Weight and Its Distribution

The weight of the bike itself and the rider also play a crucial role in determining the ideal pressure for the tires. Generally, a heavier weight would require high tire pressure and vice versa. Furthermore, the weight of gear and additional luggage should also be factored in.

A touring bike has backpacks mounted on it which increase the overall weight and hence require higher tire pressure. Road bikes, on the other hand, do not have to carry much weight apart from the rider so a bit lower pressure also works.

Moving on, this weight is not evenly distributed in most bikes. The exact split depends on the type of bike and where the additional weight is mounted. For example, in road bikes, the rear wheel has to endure more weight than the front one. Hence, it is better to add a few extra PSI to the rear tires. Tour bikes often have weight mounting spots on the front which balances the weight on both tires. Hence, extra pressure is not required in either of the two tires.

3. Terrains

As discussed earlier, tire pressure dictates the traction and road grip of the bike. Rough terrain requires better road grip to give riders full control over handling. In contrast, roads do not need as much traction because they are generally plain and smooth. Hence, riders who have to travel on bumpy and mountainous terrains should keep air pressure low. Whereas those that have the luxury of carpet roads can pump the tires to high pressure for a faster ride.

4. Weather and Temperature

When the roads are wet, it decreases the traction which can slip tires and lead to accidents. During such climates, it is better to lower the tire pressure to maintain optimal road grip and ensure personal protection.

High temperatures also increase the pressure and overinflate the tires. Consequently, it will blow up the tires and result in injuries. Hence, pressure should be kept lower in summers as well, particularly when you have a large descent on terrain. Such terrains require excessive brakes which can build up the temperature in the tires.

5. Tire Width

A certain amount of air pressure is required in all tires to prevent tubes from bottoming out on rims. The wider tires are able to hold a larger volume which means there is always enough air to stop them from collapsing. Thus, such tires can be pumped with low pressure to improve traction and road grip.

Conversely, a narrower tire cannot hold as much air which makes it more susceptible to collapse. Hence, such tires always require higher pressure than wider ones to prevent bottoming out.

Therefore, you would be able to get a comfortable ride on a 2.5-inch mountain at mere 20 PSI. Whereas 80 PSI would be required at a minimum on most road bikes for a smooth ride.  

6. Tire Material

Tires are usually made up of rubber, nylon, and cotton threads but the thickness of these materials varies in different designs. Tires designed for racing and summer use tend to have thinner nylon threads and a layer of rubber on top. This allows the tires to conform easily under pressure to deliver a faster and smoother ride.

In contrast, tires intended for winter use generally have thicker fibers which make them stiffer and more durable. Given this, riders would have to slightly drop the pressure when switching from summer to winter tires. This will provide better comfort and road grip.

Furthermore, tires that do not have the tubes should also be kept at lower pressure. With such tires, you have no risk of punctures at low pressure. This enables riders to enjoy better off-road grip and traction while riding on mountainous terrain.

How To Achieve Perfect Tire Pressure

Now that you know the recommended ranges and factors that should influence tire pressure, the question is “how to actually achieve the optimal pressure?”. Well, we have got you covered there as well.

1. Find The Sweet Spot

You are familiar with the ranges but to find the sweet spot all of the enlisted factors should be accounted for. The basic step is to factor in your weight.

For example, mountain bikes have a recommended range between 30-and 50 PSI. If you have a lighter weight you can start from the bottom whereas if you fall on the other side of the spectrum, start from the higher limit. Furthermore, understand the terrain and factor in as well.

That said, it is highly unlikely to find the right pressure in the first attempt. But after some experimentation, you would ultimately get there.

2. Check Tire Pressure Regularly

Be it tubeless tires or latex tubes, all of them leak air over time. While the former leaks far less air, it still has to be checked regularly. You can experience a loss of a few psi a week to drastic drops overnight. It largely depends on the type of tires and the climate outside.

Hence, it is important to regularly check the air pressure, particularly in summer to enjoy a smooth and comfortable ride. We recommend checking the pressure at least once a week. Furthermore, do a thorough inspection after fixing a puncture especially when Carbon Dioxide canisters are used. This gas is highly soluble in rubber and leaks out far faster than nitrogen which is commonly used for pumping up the tire.

3. Avoid Floor Pumps

Floor pumps are cheap and convenient to pump up the tire but they are not reliable as far as measuring the pressure is concerned. These measure the pressure inside the pumps rather than the pressure inside the tires. Most floor pumps are off by at least 10 to 15 psi but there are few that can give close to the actual measurement.

However, the silver lining is, that most of these pumps are consistent. Essentially, you’re pumping out the same amount of air every time. You can get around it by getting a separate gauge that is affordable, reliable, and durable. Do not purchase one if someone around you already owns one. Just borrow it and notice how much your floor pump is off. Note it and start to factor in the difference next time you pump up the tire.

4. Regularly Examine The Tires

All the tires eventually wear out regardless of the size and material. A worn-out tire not only leaks air but reduces the traction and road grip as well. Hence, it is of utmost importance to regularly check its health and replace when it is necessary. You should be able to judge it based on the depth of grooves. Sufficient depth of these grooves would imply a better condition and vice versa.

5. Try Different Pressures

Unfortunately, not all the factors that determine ideal pressure are measurable. Plus, there is no formula where all measurements could be factored in to get the right pressure. This leaves riders with only one option, experimentation. You know the recommended range, start from the bottom and make your way up.

Furthermore, analyze the design of the bike and try to understand its weight distribution. Tweak the pressure in the front wheel and take a ride. Repeat the process with the rear wheel and ultimately you would be able to achieve the right pressure on both wheels. The process will take time but once you find the right balance, it would be all worth it.

Bottom Line

Pumping the tires to optimal pressure is the quick and cheapest fix for a comfortable and smooth ride. It not only improves the overall riding experience but also increases the durability of the tires.

All the enlisted factors play an important role but weight and terrain are two that stand out. Hence, these two should be factored in at the bare minimum while pumping up the tires.

We hope this piece on bicycle tire pressure has been helpful. Let us know your queries. We would love to respond. Thank you!