MTB tire pressure is a much more important factor when it comes to mountain biking than most people think. By changing the tire pressure alone, you can have an impact on the speed, safety, comfort, performance, and even the longevity of your bike.
This article, in particular, will go over the effects that tire pressure can have when it comes to ‘tubeless’ tires. If you’re not sure what tubeless tires are, they’re exactly as the name suggests – tires with no inner tube inside.
How is that possible? Well, instead of using inner tubes, the tire is placed directly over the rim of the bike, and a special sealant is used to plug any gaps in order to prevent air from escaping. Tubeless setups have been increasingly growing in popularity over the past few years, and many people wonder why.
What Are Tubeless Setups?
First of all, tubeless setups allow you to safely run a lower air pressure in your tires. With inner tubes, running anything less than 30 PSI would increase the risk of getting pinch flats. But with a tubeless setup, there’s no risk of this, so a lower pressure can be run.
How does this help? Well, running a lower pressure means that the tires aren’t as firm and ‘bouncy’, as well as having more contact with your riding surface. This allows you to gain more grip whilst riding, as well as better traction and control over difficult terrain.
Rather than bouncing straight off hard surfaces, the tire will somewhat warp around them, absorbing the rough terrain, and preventing you from having to fight bumps and dips. As well as this, in wet or icy conditions, the tire will grip better to any surfaces, adding an element of safety, and preventing the road bike from slipping underneath you.
These are a few of the reasons why running a lower tire pressure can be a big help!
What to Consider When Deciding on MTB Tire Pressure
As you can probably expect, the optimal tire pressure depends on various factors, so there’s no set number or value that’s ideal for everyone.
Rider size and weight, bike size and weight, rider style, experience, terrain, and even things like the weather, all have an impact on what pressure would work best. But in order to find out what’s ideal for you, there are a handful of things you’ll need to bear in mind, before pumping up your own.
Some are quite straightforward, whilst others require a little more planning and investigation. Again, no PSI is perfect for every ride, but figuring out a rough benchmark makes things a lot easier in the long run.
Width of Rims
The narrower your tire, the higher pressure you’ll want to run as well – and the wider your tires, the lower the pressure.
This is because of the way the tires are designed – wider tires cater for grip, and narrower ones for speed, so your air pressure will want to compliment this in order to make the most of your ride and maximize performance.
The more you weigh, the higher tire pressure you’ll want to be running. Simply put, a heavier rider will put more downward force on the tires, so to counteract this, you’ll want to put more air inside them.
This prevents any bumps or dips in the terrain from hitting the rim and damaging the wheels themselves.
The Casing of the Tires
The tires material, construction, and casing also have an effect on what tire pressure you’ll want to be running inside. TPI (threads per inch) refers to the density of the threaded construction of the tires themselves.
Tires with a high TPI count are lighter and more flexible, whereas tires with a low TPI count are stiffer and more robust. Much like with tires width, this is due to the different intentions of the tire, so to maximize your performance, your PSI will want to compliment this.
What Kind of Terrain Will You Be Riding On?
The riding conditions and terrains are probably the most impactful factor when it comes to choosing the ideal tire pressure for you.
Riding on dry, smooth and even surfaces is a completely different experience than riding on wet, muddy, cold and uneven terrains – and therefore a different tire pressure is required! In dry conditions, especially on smooth terrain – like roads of pathways – you’ll most likely be wanting to run a higher tire pressure than usual.
This will allow you to maximize your speed and momentum when riding along the surface, for increased performance. When it comes to uneven terrains, however – such as dirt trails and hills – especially in wet or slippery conditions, you’ll want to drop the tire pressure a little bit, to increase the amount of contact your tires have with the riding surface. This will provide you with extra grip and control, as well as help prevent slips and slides on corners.
It’s important to note though, that if you’re a particularly fast-paced or aggressive rider, you don’t want to drop the pressure too much. Although low pressure gives you more control, it also offers less protection for the rims, as the air in your tires often acts as a safety barrier between the bumpy terrain and the rims themselves – so bear this in mind.
Rear vs. Front Tire
Casual riders tend to ignore this rule, but more serious and competitive riders don’t – sometimes it’s a good idea to run your rear tire at a slightly higher pressure.
This is for two main reasons – because of where you sit on the bike, as well as the bike composition itself, there tends to be slightly more weight on the rear of the bike than on the front.
As well as this – especially when it comes to hardtail bikes – rear wheels tend to absorb more bumps and jolts, so the added PSI helps them absorb this without the bike getting damaged.
What’s Considered a Good Starting Pressure?
This one’s a hard one, as it really differs a lot from one rider to another. Most seasoned bikers will agree that 25 PSI acts as a good benchmark for mountain bikes.
If you’re more on the heavier side, 26-28 PSI might be more suitable, whereas if you’re lighter, you might get away with running 24 PSI. From this pressure, increase or decrease the PSI depending on your riding style, needs, and terrain.
What About Plus Bikes?
You’ll likely want to run a lower pressure on ‘plus bikes’ due to the width and volume of the rim and tire. Start in the 15-18 PSI range and adjust accordingly from there.
Again, depending on your weight, terrain and riding style, you might want to increase or decrease the pressure from this mark, in order to find the ideal pressure that works best for you.
Figuring Out the Range of Tire Pressures
There’s only one way of finding out for sure what tire pressure works for you on your bike and with your riding style, and that’s by trying it out yourself.
Get yourself a pressure gauge (or buy a pump with one included), and pump your tire up to a benchmark number (preferably 25 PSI). From here, ride around on different terrains and in different weather conditions, and adjust the pressure depending on how you find the ride – making sure to keep a note of what pressures work in what conditions.
What worked best on the trail vs. the road? Did dropping the pressure increase or decrease the control on the corners? Take note of these whilst riding, and this way you can keep track of what pressures worked well in what areas and what didn’t, and before long, you’ll know exactly what number to aim for in whatever conditions you find yourself in.
Your ideal MTB tire pressure will be different from most other people’s – but as long as it works for you, that’s all that matters!
Does Temperature Affect MTB Tire Pressure?
Temperature also affects the tire pressure of your tires in a number of ways – so knowing and understanding these will help you keep safe, and prevent any unexpected changes when out on the trail.
The first is that, when pumping up tires indoors, after taking the bike outdoors, the change in temperature between the two can increase or decrease the PSI inside the tires. Because of this, it’s important to bring a pressure gauge out with you, so you can double-check the pressure when out on the trail.
As well as this, lower temperature conditions (especially close to zero degrees C) are more likely to make any surface slippery and reduce grip. Regardless of your bike, tires or riding style, it’s recommended that you drop the pressure a few PSI during the winter months, as this will provide that extra contact with the riding surface and therefore that added grip when riding, just to keep you safe.
The same goes with ultra-hot temperatures, as these can make the ground firmer, drier and dustier, so it’s important to bear this in mind and adjust the PSI in preparation for this.