While the pressure in your mountain bike tires isn’t always a hot topic of discussion in the mountain bike world, it can be much more important than you may think.
Having the wrong tire pressure can make your ride a lot bumpier, can reduce your traction on the trail, and can even be dangerous. By contrast, getting the right PSI in your MTB tires can make your ride much smoother and give you the confidence you need to corner at speed and rip your favorite trails to shreds.
| Rider Weight (lbs) | PSI Starting Point - Front | PSI Starting Point - Rear |
|---|---|---|
| 90-110 | 16 | 20 |
| 110-135 | 17 | 21 |
| 135-155 | 19 | 22 |
| 155-175 | 21 | 23 |
| 175-200 | 24 | 25 |
| 200-220 | 25 | 27 |
| 220-245 | 27 | 29 |
Key considerations to finding the right tire pressure for you
Rider weight
Rider weight can make a significant difference in how much riders should pump their tires up. As a rule of thumb, the heavier you are, the more air pressure your MTB tires will need.
Riding style
How you approach trails and your riding style definitely affect which tire pressure you should be using. If you’re an aggressive rider who attacks trails and goes over, not around, major obstacles, especially while carrying speed, you will need to make sure you have enough air in your tires to prevent both flats and damage to your rims.
If your approach to riding is more about avoiding the major obstacles but you want some extra traction and smoothness over smaller bumps, you will be better served running lower pressure in your MTB tires.
If you mainly do cross country mountain biking on smoother trails and speed is what you’re most concerned with, you will be best suited using higher pressure in your tires because this will reduce your rolling resistance to make you faster.
Trails and terrain you ride
If you do most of your mountain biking in rough terrain, you will want to make sure your mountain bike tires to have enough tire pressure to prevent flat tires and damage to your wheel rims.
As long as that is accomplished, you will enjoy both a smoother ride and better traction if you keep your tires at a lower pressure over bumpy trails.
Just keep in mind that you will still need enough air pressure in your tires to prevent damage on the hardest hits your tires/wheels have while out riding.
So if you’re hitting big jumps, or drops to flat landings, or if you do occasionally ride over bigger obstacles at speed, you will want to make sure you have enough tire pressure to withstand these impacts.
If you ride on mostly smooth trails with few rough or bumpy sections, you will be better suited to riding with higher pressures because this will reduce the rolling resistance you face which will allow you to rip through trails faster.
Tire width
The width and overall size of your tires will affect what tire pressures you will be able to run.
The wider and larger your tires, the lower tire pressure you will be able to run, and conversely, the smaller your tires, the higher the pressure your tires will need.
Fat bikes are a great illustration of this concept. Because they are designed to be used in situations with lower traction, fat bike tire pressure is normally kept quite low.
This allows for the tires to have a greater contact patch with the surface they’re on, improving traction for fat bikes in snow, on sand, or on other loose terrain.
Plus size tires, found on 27.5-plus mountain bikes, are also larger than normal mountain bike tires and therefore can be run at lower tire pressure.
Ordinary mountain bike tire width can range from 2.2 inches to 2.5 inches, and all else being equal, the 2.5-inch tires should be inflated more than the 2.2-inch ones.
Inner tube vs tubeless tires
Some mountain bikes have inner tubes in their tires, while others are set up with tubeless tires, meaning they do not have inner tubes. Instead of inner tubes, the tires, rims and valves are designed in a way to remain perfectly sealed which keeps tubeless tires from going flat.
Tubeless tires allow mountain bikers to ride with lower tire pressures because they eliminate the risk of pinch flats which are fairly common with inner tubes.
Weather and trail conditions
The trail conditions you ride in affect what tire pressure you should ride with. If its rained recently and the trails are wet, things will be more slippery than normal, and to help offset this riders can lower their tire pressure to increase the contact patch their tire has with the trail, improving their traction.
This also works well if you ride in the snow, on sand, or trails that are not packed down and have loose, slippery surfaces.
Wheel size
All things being equal, bikes with larger wheels can run lower tire pressures. This is because a 29-inch wheel will have lighter impacts on obstacles compared to a smaller wheel size, such as 27.5 inches.
Lower tire pressure is better – to a point
Many mountain bikers believe that lower pressures will result in slower rolling speed. While this is true on smoother terrain, it isn’t so true on bumpier trails, because tires with higher pressures will not deform over uneven surfaces, like rocks and roots, nearly as well as tires running lower tire pressure.
As a result, you’ll usually be better keeping your tire pressure as low as you can while still allowing the tires to have enough structure to maintain traction and prevent flats.
Trying to get your tire pressure too low can both compromise your traction and result in unwanted and unneeded flat tires.
In addition, your wheel rims can be exposed to damage much more if your tire pressure is too low, since your tires can deform enough when hitting obstacles that those obstacles actually dent your rims.
Indicators your tire pressure isn’t right for you
Poor traction
Poor traction can result from your tire pressure being too low OR too high.
While low pressure will generally give your MTB tires better traction on the trails, if its too low, the tires can begin to lose their shape and structure on corners, and can start to feel sketchy and unpredictable.
This in turn will hurt your confidence when approaching other corners, not knowing if you can trust your tire to hold the line you’re trying to ride.
Alternatively, if your tire pressure is too high, your contact patch with the ground will be reduced which will reduce the amount of traction you have, especially on trails that are slippery either due to water, snow or because they are not well packed.
Ride feels harsh and bumpy
Another indication that your tire pressure is too high is if you’re noticing the trails feel bumpier than normal and you find yourself getting bounced around by the terrain.
Impacts with rocks, roots and other obstacles will feel harsh if your tires aren’t soft enough to allow them to deform some and absorb some of the impact of obstacles.
How to check your mountain bike tire pressure
The best way to check your tire pressure is by using a tire gauge. This will allow you to measure how many PSI (pounds per square inch) your MTB tires have.
Keep in mind that not all air pressure gauges are the same, and there can be quite a bit of variance from one gauge to the next. For this reason its recommended you always use the same pressure gauge when measuring your tires to make sure you are able to keep your tires’ air pressure consistent.
So what tire pressure should I use?
As we mentioned, the right tire pressure for you will depend on things like your weight, riding style, the types of trails and terrain you ride, the width of your tires, whether you run your tires with inner tubes or tubeless, and also your wheel size.
Front tire versus rear tire
The rear tire on your bike generally has a lot more force applied to it while riding. It carries more of your weight, and takes much more impact from hitting obstacles (this is especially true if you ride a hardtail!).
For this reason, you will want to keep higher pressure in your rear tire compared to your front tire.
Air pressure estimates by weight
Below is a handy table that should be used as a starting point for the pressure in your tires. Keep in mind that this will also depend on the other factors we talked about above which is why we emphasize these are only a starting point to finding the right tire pressure for you:
| Rider Weight (lbs) | PSI Starting Point - Front | PSI Starting Point - Rear |
|---|---|---|
| 90-110 | 16 | 20 |
| 110-135 | 17 | 21 |
| 135-155 | 19 | 22 |
| 155-175 | 21 | 23 |
| 175-200 | 24 | 25 |
| 200-220 | 25 | 27 |
| 220-245 | 27 | 29 |
Frequently asked questions
The PSI you should run in your mountain bike tires depends on a variety of factors including your weight, the types of trails you ride on, your wheel size, and whether your tires use inner tubes or are tubeless.
A good starting point for someone weighing between 155 and 170 lbs is 21 PSI in the front tire and 23 PSI in the rear.
Yes, all things being equal, a mountain bike with 27.5 inch wheels should run a higher PSI in its tires compared to one with 29 inch wheels, because 27.5 inch wheels do not blunt the impacts of obstacles you’ll hit on the trails as much as 29 inch wheels do.
Running too low of a pressure on your 27.5 inch MTB will result in more flat tires compared to the 29er, and you’ll be more likely to damage your rims.
Conclusion
There you have it – while there is no one-size-fits-all answer to the right tire pressure for your mountain bike, you should consider your weight, wheel size, the types of trails and riding you like to do, and the trail conditions and how slippery they are.
While lower pressures are generally better, make sure you don’t go too low and mess with the stability and structure of your tires. Once you have figured out the right pressure for you, make sure you have a gauge handy to keep things consistent. Now get out there and ride!