How do you determine what the optimal mountain bike tire pressure is for performance? One of the biggest mistakes that some mountain bikers make is that they disregard the importance of tire pressure. For purposes of this post, I’ll be referring to a tubeless tire set-up because you can run a lot lower pressure without tubes! If you start riding in new places, in very dry or very wet terrain, focus on rock gardens, or even change disciplines from XC riding to more of a trail riding style, you’ll want to reconsider your tire pressure.
But why would you want to run low tire pressure? Will a higher tire pressure mean that you go faster? Not necessarily.
Back in the day of tubes, we had to run 30 PSI or higher in our mountain bike tires. If we went much lower, there would be a risk of pinch flatting, or compressing and poking a hole in the tube between the tire and rim. I like using the analogy of a basketball for tire pressure. If a basketball is full of air and you bounce it, the ball will rebound hard and quickly off the surface. In effect, if your mountain bike tire is too hard, you’ll hit a rock or root and bounce right off of it. The benefit of running lower tire pressures on singletrack allows for better traction and better ability to navigate technical sections. The tire will morph over the rock instead of bounce or slide off it so you don’t have to fight the trail. On loose sections, the tire will grip the trail harder instead of slide off the top layer of dirt.
The first part of this post is the SHORT VERSION with general guidelines if you want to majorly simplify your tire pressure. The second half is a very detailed guide to tires including several variables you can play with.
Short version
There are a lot of variables that can affect your tire pressure. However, you can simplify it and tweak as you go and based on experienced if that is your preference. The basic advice below is explained in greater detail in the long version if you’re curious about why or want more specific information. In general, you’ll run about 2-3 PSI less pressure in your front tire to help with steering traction and a little more in the rear because you typically hit things harder with your back tire.
For XC:
Your weight will change how much pressure you run. A 170-180lb pound man can start around 25-27 PSI. I’m about 130lbs and I start around 20-22 PSI for wider tires. You can run less tire pressure if you are running wider tires like 2.35. If it’s wet, drop your PSI by 3-5 PSI. If it’s dry and really rocky, go on the higher end. You can run lower pressures for XC because the speed at which you hit rocks is typically slower because you are limited by your suspension.
For Trail Riding (140mm+)
You’ll want to start with a higher pressure. I learned this the hard why at an enduro stage race where I had some flats because I was running my XC pressure. You hit things harder because you can. On a trail bike, you hit rocks and roots and don’t feel them like you would on a smaller travel XC bike. For trail riding, I’d add 5 PSI to the XC guidelines as a starting point. Another thing to keep in mind is that tire tread will be different on trail/enduro tires, typically with less but taller knobs meaning you’ll need to lean the bike more to get the tire to bite. I’m working on a post demystifying tire tread so stay tuned or sign up for my newsletter so you don’t miss it!
I love the Topeak JoeBlow Mountain X that came out this year for pumping up my tires before each ride. It’s a mountain bike specific pump so you actually don’t have to spend as much time pumping your tires. Why? The barrel is wider so it pushes more volume per pump and you aren’t using your whole body weight trying to get the pump handle down! (fun stat: it inflated 50% faster than your regular pump).
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Long Version
So how much pressure should you actually be running?
I wish there was an easy and exact answer, but the truth is it varies for everyone. In fact, it can vary based on trail conditions and riding style for the same rider. To find out what works best for you, there are a few variables to consider. The first 4 are easy. The last two require some trial and error. It doesn’t take long to figure out what you like, but knowing why you are adding air or letting air out is helpful!
- Rider Weight
- Rim Width/Tire Volume
- Tire Compound/Casing
- Rear vs. Front Tire
- Wet or Dry trail?
- Rocks, Roots, or Pretty Smooth?
Rider Weight
Heavier riders need to run more pressure. Someone who weighs 130lbs will run less pressure than someone who is 160lbs. Because- gravity.
Rim Width
The wider the rim, the lower the tire pressure you can get away with due to surface area and volume. On a fat bike, you can run as low as 5PSI for traction. Plus bikes? I’m running in the teens for PSI. 2.2 to 2.4 inch tires? I’m running in the low to mid 20s. Rim width is often designed for an ideal range of tire widths that can be found on the manufacturer’s website. You wouldn’t put a 2.8inch tire on an XC rim simply because of the tire footprint and the way the tire will expand with inflation.
Tire Compound and Casing
Tires are made with different compounds for different tire weights. I use Maxxis tires and they have different compounds for grip and also different threads per inch (TPI). A higher TPI will be lighter and give a more supple/flexible feel whereas a lower TPI will feel stiffer and will be more puncture and roll resistant. XC tires tend to have higher TPI while downhill tires tend to have lower TPI. For example, use a tire with 120 TPI for added suppleness, trail feel, and less rolling resistance for XC tires, and 60 TPI for added support and durability for more demanding trail/enduro conditions.
Wet or Dry Trail? Rocks, Roots, or Pretty Smooth?
If you are riding wet, rooty trails (something I learned the hard way my first time riding in BC), you actually want to drop the tire pressure even lower than normal. For example, I typically use 20-22 PSI on Maxxis Ikon 2.35 tires on Stans Crest CB7 Carbon wheels. For a wet rooty trail, I’d run closer to 17. Dry trails can afford a higher pressure because they aren’t as slippery. If the trail is really loose, you can drop the pressure down by a couple PSI. If you are slipping around in corners, you can try a lower tire pressure as well (reminder: do your best to brake before the corner!)
If you are pretty aggressive and plow through rock gardens, go fast off hucks, or are doing more trail/all-mountain riding, you need to increase the pressure. For this style of riding, I increase my pressure to 25+ PSI. The reason is that you are hitting obstacles so hard and so fast, that the force will be multiplied. If you hit the ground harder off a jump or smash into a rock garden at a faster speed, you need more pressure to handle the force or there is a risk of flatting. I learned this the hard way in my second enduro stage race. You have more suspension so you can hit things a lot harder at higher speeds, but the tire pressure also needs to be adjusted.
Rear vs Front Tire:
Most people run more pressure in their rear tire (usually 2-3 PSI more) because there is more weight on your back tire. The back tire also tends to take more of a beating. A sample tire pressure for me would be 22 PSI rear, 20 PSI front. Again, with a wider tire, you can run lower like 20 PSI rear, 18 PSI front.
Where’s a good starting pressure?
Generally, starting at 25 PSI is a good place to start for XC. If you are riding more all-mountain/endure, start with 28-30PSI. Keep in mind that these numbers are based on your weight as a rider. Larger riders will have to run higher pressures, but this is a good starting point. A baseline range for the aforementioned pressures is 185 lbs and below. If you’re more than 185, add more PSI. If you’re a lot less, start with a little bit less.
Plus Bikes?
Again, pressure can vary, but generally you’ll run a lower tire pressure on a plus bike due to the rim width and sheer volume of the tire. A good guideline is start for the front tire is 16 PSI if you’re a bit bigger. If you’re 140 lbs or less, try 12-14 PSI. If you’re more? 13-16 PSI? 180lbs +? Try 16-18 PSI. Add a couple PSI for the rear tire. Again, it’s preference, riding style and conditions can change your pressure, but this is a good start. I run about 11-12 PSI (and am 130 lbs) on my Maxxis Rekon 2.8s.
Where to start to figure out a range of pressures that work for you and your riding style?
Trial-and-Error. One of my most important tools is my Digital Pressure Gauge. I like the Topeak D2 Digital Gauge. It’s light and fits in my pack so I can take it on the trail. I use it on the fly to make adjustments. If I am want something a little heavier duty that I can also use to see the digital pressure as I use my floor pump, I use the Shuttle Gauge Digital. Both have an air release button that is super convenient. In an XC race situation, I set a general pressure before the race. For Enduro, I might change my pressure for different stages. Getting comfortable with letting air out of the tires and learning how the bike responds is time well spent. Ride the same trail a few times and experience with 2-3 PSI increments and see what you like.
If you want to learn more about pressure gauges, here are some resources:
How to Use a Digital Gauge
How to know if you have too much pressure:
You are sliding on the dirt and bouncing off of trail features. Traction will feel poor.
Too little pressure?
The tire will feel bendy, you can lose or burp air on rocks or corners, and it can roll off the rim in extreme cases. It can feel like you are dragging extra weight uphill. You’ll also hear blows to your rim or dings when you go over rocks. If you hear that sound, add more air.
A Note on Temperature:
I’d recommend checking your pressure again at the trail. The temperature in your garage versus outside can effect the pressure. For example, if you set your pressure in a 74 degree air conditioned environment, put your bike on the car and drive to the trail where it’s 80-90 degrees, the tire can end up several psi higher than you thought just due to the change in air temperature.
Tire pressure is pretty individual, but knowing all the different elements that are involved in setting your pressure and how to adjust based on conditions is really valuable. I had ZERO flat tires this year in all of my training and racing from good tire choices (I tend to run a little heavier than other XC racers because I’d rather drag the weight then worry about flats), having Stans Race Sealant, and rims I can trust. A lot of trial and error with tire pressure has enabled me to optimize my technical riding and prevent flats!
If you find that you are riding upwards of 35 PSI and your tires still feel like they are squishing and moving too much, try a different, tougher tire with lower TPI.
Note: I run lower tire pressure in my training rides then I do in my races. In races, I tend to ride very aggressively on the descents on my XC bike. Also, slightly more tire pressure for climbs can be good if the climbs aren’t technical. If it’s wet, I drop the pressure. Lots of technical climbing too? Lower tire pressure will help with traction getting up and over roots and rocks on the climbs as well.