Are your tires inflated just right or are they a little low on pressure? What if you overfilled your tires? Neither are great scenarios to be in. Underinflated tires are likely to lead to a whole host of issues.
These include some tires wearing down faster than others, heat building up in the affected tire, difficulty braking, and a decrease in fuel economy. In some situations, your tire could even come off!
Overinflated tires aren’t much better. You’ll be uncomfortable as you ride since your overfilled tires handle differently. Your contact patch is lessened as well. Also, although it’s unlikely, overinflated tires could explode in certain conditions.
That’s why having the right tire pressure is so important. It’s not just for a smooth ride, but for a safe one, too. In this article, we’re going to tell you exactly what you need to know about bike tire pressure.
What’s the Correct Tire Pressure for a Road Bike?
Let’s begin by discussing the tire pressure for road bikes and mountain bikes. What is the correct tire pressure for a road bike? There’s actually no one specific answer.
That’s why we recommend you consult your bicycle owner’s manual to get a tire pressure range to follow. If you by chance lost your owner’s manual, you can always check out this handy chart.
|Tyre Width||60kg / 132lb||85kg / 187lb||110kg / 242lb|
|23c||7 bar / 100 psi||8 bar / 115 psi||9 bar / 130 psi|
|25c||6 bar / 87 psi||7 bar / 100 psi||8 bar / 115 psi|
|28c||5.5 bar / 80 psi||6.5 bar / 94 psi||7.5 bar / 108 psi|
|32c||4.5 bar / 65 psi||5.5 bar / 80 psi||6.5bar / 94 psi|
|37c||4 bar / 50 psi||5 bar / 72 psi||6 bar / 87 psi|
Table courtesy of Cycling Weekly
As you can see, road bike tire pressure is dictated by several factors. These include the width of your tires and your weight.
Since this is a UK resource, the tire width is in centimeters. Let’s say you had bike tires that are 23 centimeters or about nine inches. You weigh 187 pounds. That means your tire pressure should be 115 pounds per square inch (PSI).
Let’s do another example. Now you have a bigger bike, one with tires that are 37 centimeters or about 15 inches wide. You weigh 242 pounds. You’d need a tire pressure of 87 PSI.
The bigger your tires, the lower the PSI. Just look at the above chart for confirmation of that. Tire pressure needs will always increase with your weight.
What about for a Mountain Bike?
If you’re riding a mountain bike instead of a road bike, the tire pressure is not going to be the same. According to ENDURO Mountainbike Magazine, the PSI varies if you have tubed or tubeless mountain bike tires.
If you use tubed tires that are between 2.35 and 2.4 inches, the pressure per tire should be 29 PSI. For tubeless tires that are the same size, the pressure should be slightly lower, just 26 PSI.
For larger tires, such as those that are three inches or bigger, the PSI increases. For tubed tires of that size, it’s 20 PSI, and for tubeless tires, it’s 18 PSI.
How to Check Your Bike Tire Pressure
If your bike tires aren’t completely empty, then they have at least some pressure. How do you know just how much pressure is okay and if your tires need to be inflated more (or even less)? You have to learn to read your bike’s tire pressure.
We recommend you use a tire pressure gauge if you’ve never tested the tire pressure of your bike before. While you can get a read without a gauge (and we’ll tell you how later), it can be difficult if you’re inexperienced.
First, you want to park your bike somewhere. Next, you want to figure out which type of valve your bike has. Here’s a pretty good guide we put together that should help you identify the valve on your own bike.
Once you’ve got that figured out, you need to connect the pressure gauge to the valve. Now apply some downward pressure. You should see the gauge’s needle jump up. The pressure reading you get is how full your tires are.
If your tire pressure is good, then you can hop on your bike and keep riding. If the pressure is higher than you want, you’ll want to release some air. Depending on which type of valve you have, the way you do so varies.
For instance, if yours is a Presta valve, then you’ll want to find the top of the valve and turn it. Now push down on the valve and you should hear air coming out. Do this in increments, checking the tire pressure as you deflate. You don’t want the tire pressure to be too low!
If it is, you can always fill the tires back up again. You have several options for doing so:
- a CO2 inflator
- a mini pump,
- or a floor pump
If you want to know the differences between inflators and pumps as well as which products we recommend, click here.
Can You Check Your Bike Tire Pressure without a Gauge?
No gauge? No problem! You’re not necessarily out of luck if you forgot your gauge at home or don’t have one to begin with. There are still ways to read your bike’s tire pressure. Let’s discuss these methods now.
The first one entails you grabbing your bike tire between your index finger and thumb. Squeeze the tire. If it feels a little empty, you might want to fill the bike up. If the tire feels very firm, then the tire pressure is likely too high. You should be able to pinch the tire ever so slightly. That tells you the pressure is good.
Another trick is using puddles to your advantage. Ride through a puddle and then to dry land. Do your bike tires trail a lot of water behind you? If you have a thicker water trail, then more of the tire was hitting the ground beneath the puddle. That means you could probably afford to inflate the tires up a little.
If you want a more scientific, reliable method of testing your bike’s pressure without a gauge, try a calculator. The PSI Calculator is a great choice. It accommodates for tire drop, which we’ll discuss in the next section.
Here’s what you have to calculate:
- How much your bike weighs
- How much you weigh (adding that to your bike weight)
- Tire length in millimeters
- Weight distribution of your bike
Once you have all that info, you’re good to go! The PSI Calculator will give you both the front and rear PSI for your bike tires. We recommend saving the calculator link to your phone and bringing it up when you’re on-the-go and want to test your tire pressure.
If you’re new to biking and testing your tire pressure, the PSI Calculator especially is a great replacement for a gauge. It takes a lot of the guesswork out, which ensures more accurate PSI readings even as a beginner rider.
Why You Need to Check Your Bike Tire Pressure Regularly
No matter which type of bike you have, be it a road bike, a mountain bike, or anything else on two wheels, tire pressure is not one and done. Once you know your tire pressure, that only really applies to that one ride. The next time you go out on your bike, you’d ideally want to test your tire pressure again.
While any small weight fluctuations on your part are unlikely to influence your tire pressure, there are many other factors that could. How long did you ride? Using your bike will cause gradual tire pressure shifts.
Another major factor when it comes to your bike’s tire pressure is where you ride. Here’s a chart that appeared in Bicycle Quarterly to show you what we mean.
Image courtesy of Bicycle Quarterly
This chart, which comes from Frank Berto, measures what’s called tire drop. This determines the effect that pressure and load has on a tire. When this chart was first published, which was more than 20 years ago, it was determined that the tire drop should be about 15 percent.
Since today’s tires are bigger than those measured in the original chart, that tire drop percentage doesn’t hold as true anymore. Your tire drop may be higher or lower than 15 percent, but not by a huge margin.
Finally, one of the biggest factors that changes tire pressure is the weather. According to a 2014 Patch article, when the temperatures outside go up by 10 degrees Fahrenheit, your pressure will increase by at least one PSI. If it’s colder weather and you’re riding outside, for a 10-degree temperature drop, you’ll lose one PSI or more.
This time of year then, when the weather is still incredibly cold, you’ll more likely lose tire pressure. That means you can fill the tires on a Monday and by Wednesday you’ll have to fill them again because the weather is making you lose pressure.
You have to be careful in the summertime as well. After all, when you fill your tires, you get them to just about the correct pressure. All that heat and humidity can boost the tire pressure, which puts you at risk of overinflation. Test your tire pressure often!
Your bike’s tire pressure is not a static number. It changes depending on your weight, the bike weight, the type of bike you use, and the types of tires. The terrain you ride on and the temperature outside, hot or cold, can also increase or decrease the PSI.
That’s why we recommend you test your tire pressure often, at least every day before you ride. Whether you use a gauge or a calculator to get the right number, if you take care of your tires, they’ll take care of you.