Mountain Bike Tire Pressure – What You Need To Know
Russell Franklin - October 18, 2022Soft tires typically have slower rolling speeds. This is wildly exaggerated on mountain bike trails. Harder tires actually tend to bounce because they can’t properly grip the track. Hard tires’ reduced friction and prolonged time off the ground, especially when using lower gear ranges, can significantly slow down a rider’s speed. Not always do the best mountain bikes have the highest tire pressure.
Mountain Bike Tire Pressure
One of the new riders mentioned running 27 psi when they remember to check when the topic of tire pressure was brought up during a conversation with some other new riders the other day. This particular athlete developed a new pandemic interest in trails over the summer, and she now rides a few times a week. She also has a weight of 125 pounds, which made me wonder why she decided to run at such high pressure.
“Someone at the bike shop told me to,” she said. This was undoubtedly a false assumption, as bike shops are frequently the best resources for information on the majority of MTB-related topics.
My friend enquired as to whether or not that figure seemed accurate and how she could figure out a more exact pressure for her weight and riding style. There are countless approaches to determining the ideal pressure, and the outcome is unquestionably individualized. Using a formula I discovered on the Stan’s NoTubes website when they first began producing tubeless sealant has always been a good place to start for me.
For the front tire, use the formula (rider weight in pounds divided by 7) + 1; for the rear tire, use the same formula + 2. That comes out to 17.9 psi for my friend, or 125 lb divided by 7. Therefore, she would want to apply about 17 psi under the bars and 20 psi under the saddle. Small adjustments made to account for terrain, temperatures, and other significant variables have always made this formula effective for me.
The best way to find your ideal tire pressure after performing the calculations above is to go for a ride. The front tire may be too low for your body position and the dirt surface once you get on the trail. You might want to add some air if you’re rolling your preferred speed down a favorite descent and you hear the rim hit rocks and roots repeatedly. Contrarily, you might want to lose 1-2 psi and reevaluate if the rim never bottoms out at maximum speed and you’re having trouble maintaining traction. If you have tread that is suitable for the trail surface and your riding style, the right pressure will help you get the most grip possible and move more quickly.
Check Tire Pressure Regularly
Even properly installed tubeless tires for bicycles leak air occasionally. The typical drop is a few psi per week, but depending on usage and environmental factors, drops can be more dramatic. For example, a tire’s pressure will drop by 2% for every 10 degrees Celsius drop in temperature because the air inside the tire puts less pressure on the tire wall. You can prevent any unpleasant surprises and tire punctures by regularly inspecting your mountain bike tires. Never exceed the manufacturer’s recommended maximum pressure when you do pump up the tires!
What Elements Affect The Pressure Of Mountain Bike Tires?
The “right” tyre pressure for you and your bike depends on a variety of factors, as we’ve already mentioned. Let’s go over them.
Rider And Bike Weight
Starting with the weight of you and your bike together makes sense. A heavier rider and bike will logically require higher pressures than a lighter rider.
Why? Because a heavier rider will exert more force on the tires, higher pressures must be used to counteract this. For a lighter rider, the reverse is true.
Terrain
Also, where are you planning to ride? You might need to slightly increase your pressure if you’re riding in an area that is extremely rocky and rooty, perhaps on fast terrain where you might be hitting those features quickly.
Though if pressures are too high, you may increase the risk of tearing your tyre’s carcass on a sharp edge. Higher pressures mean less tyre deformation when you hit a rock, and therefore less chance of it puncturing.
In contrast, lower pressures will allow the tyre to deform more and better conform to the shape of the ground, increasing grip, if you’re riding on smoother terrain or perhaps at lower speeds (think super-steep muddy and rooty tech trails).
As you’ll see, there’s also some subtlety to appreciate here: a track in the dry might behave very differently when it’s wet, so your pressures might need to adjust based on the state of the trail.
Riding Style
Even though it is less “measurable,” a rider’s style may also be taken into consideration.
You might get away with a few psi less if your riding is a little bit more precise and you weave smoothly through obstacles. However, you might need to focus a little more on puncture protection if your shooting style is more point-and-shoot.
The Best Tire Pressure Also Depends on You
You should consider rider weight when inflating your tires, just as you should when tuning your suspension to the weight of the rider. The force applied to the tires by heavier riders (weighing 175+ lbs) will be greater than the force applied by lighter riders (weighing less than 150 lbs). Canyon’s own Scott Hart, a lighter rider, rides trails on his Torque set up to the following:
- Front: 25 PSI
- Rear: 27 PSI
As you can see, Scott rides a few PSI lower than Braydon, and heavier riders may need to set their front and rear tires to 30 and 32 PSI, respectively. Don’t go below the printed minimum pressure or above the printed maximum pressure (typically between 20 and 40 PSI), which are printed by the majority of tire manufacturers as ranges on the tires themselves (assuming tubeless setup).) The tire may roll or “burp” if there is insufficient air, and it may blow off the rim if there is too much air.
What Tires And Rims You Run
Just as important a role is played by the rubber you select. Pay attention to your casing! Is the tough dual-ply carcass made for aggressive enduro riders, such as MAXXIS Double Down or Schwalbe Super Gravity) or a thin single-ply tire that puts weight reduction over puncture resistance (e.g. SCHWALBE SNEAKE SKIN and MAXXIS EXO)? Whether or not your bike is set up tubeless is another critical consideration. Since there is no tube between an obstruction and the rim of a tubeless setup, lower pressures can typically be used, preventing the dreaded “snakebite” puncture. Wider rims provide the tire with more support and have a higher volume, allowing you to run lower pressures without sacrificing performance.
For Tubeless Tires, What Pressure Should I Use?
As was previously mentioned, tubeless tires can be operated at lower pressures without the risk of “snakebite” punctures. However, the ideal tire pressure for a tubeless tire also greatly depends on the previously mentioned elements and, as a result, varies depending on riding style and terrain. We requested information about the personal setups of our editors so that you could get an idea. Never learned of tubeless? Everything you need to know about tubeless setup, tires, and more is covered in our comprehensive MTB tubeless guide!
How To Find Your Perfect Tire Pressure – Field Testing
The trails must be explored now! You should locate a quick, one- to two-minute test loop and arm yourself with a pump and gauge. You want to be able to focus on the ride feel, not trying to stay out of the bushes, so make sure it has some nice flat corners, berms, compressions, and roots, representative of the terrain you ride without being too gnarly! Start off by setting your tire pressure high at first so you can experience that. In the front, try 28 psi, and in the back, 30 psi.
How To Lower Your Tire Pressure With Inserts
There are many different tire insert brands and designs available, but they all essentially serve the same purpose, albeit in some cases more effectively than others. The two purposes of tire inserts are as follows. They serve as a protective cushioning layer for the rim, intended to deflect any blows from rocks or roots that might otherwise “bottom out” the tire. Second, inserts are said to improve tire stability by forcing the tire’s sidewalls into the rim’s bead. With the best inserts, you can run your tubeless tires at lower pressures without sacrificing rim safety or tire stability.
Conclusion
Tire pressure is the simplest and least expensive bike tune-up, whether you want to perfect your setup or simply use our recommended pressures, as you will quickly discover. You’re well on your way to getting more grip, control, and fun out of your bike once you realize how different tire pressures affect performance.
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