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By now most of us know that low tire pressure in our mountain bike tires is the way to go. Tire pressure is a hot topic (and probably has been since the invention of mountain bikes) and there are a ton of articles out there giving advice on how to properly set your tire pressure for different conditions and for different-sized tires.
I want to take a closer look at the benefits of lower tire pressure.
This isn’t one of those articles. Instead of debating the difference that one or two psi makes in different conditions and on different surfaces, I want to take a closer look at the benefits of lower tire pressure. Advances in technology, namely tubeless tires, have allowed for lower tire pressures and riders have gravitated toward it. But why? Didn’t conventional wisdom used to dictate that you had to pump your tires up as hard as they go and reap the rewards of low rolling resistance? It sure did, but things have changed and there are real reasons to lower your pressure. In fact, low pressure actually allows you to ride faster and longer!
Let’s dig in…
What do I mean by low pressure?
I’ll save you some time. I’ve looked through a lot of articles, comments and manufacturer websites (not to mention my own experiences) and found that tire pressure recommendations for mountain bike tires are generally between 15 and 30 psi.
For the most part, the low end of the range is for lighter riders on lower volume tires and the opposite is true for the higher end. For example, at the extremes of bicycle tire volumes, a very high volume 5-inch fat bike tire might use 4 – 7 psi, while a road tire might use 90 – 120 psi. The range for mountain bike tires is much smaller than between fat bike tires and road bike tires, but the principle remains the same.
I’ve got friends in low places
As noted above, 15 – 30 psi seems to be the normal range these days for mountain bike tire pressure. Literally everyone I ride with uses a low tire pressure of below 30 psi, except for one person who still uses tubes. There is a case to be made for using higher pressure when tubes are involved, but it isn’t done for performance reasons. It’s simply a way to keep from getting pinch flats. And let’s face it, tubes in mountain bike tires are becoming more of a relic with each passing year.
Don’t believe that lower is better? Let’s take a look at what some of the pros are doing. They’re always on the cutting edge of what’s popular, trendy, and most importantly, performing well.
Here are three tire pressure setups from three of the top pros in their respective mountain biking disciplines:
Rachel Atherton (DH) – 25 psi
Sam Hill (Enduro) – 23 front psi, 28 rear psi
Geoff Kabush (XC) – 20 – 24.5 psi
As you can see, the pressures are all well under 30 psi.
Nobody likes a high-pressure situation
So why then are riders willing to sacrifice the low rolling resistance that comes with high tire pressure? Because overall, lower tire pressure is more efficient. As mountain bikers, we’re (almost) always looking to maximize speed and minimize fatigue, and low tire pressure helps in both of those departments.
The need for speed
Speed is great in mountain biking, even when we’re not racing. Descending fast is fun and the faster we go the more fun we can have (at least up to a point)! Climbing fast may not be as fun as descending, but for those who love to climb, it can be exhilarating in its own right. Not to mention more climbing speed gets those tedious climbs out of the way faster so we can move on to the descents. Low tire pressure helps to increase speed on both the climbs and descents in a couple of important ways.
First, it allows for more grip as the tires can flatten out and have more contact with a loose surface. Descending, this improves grip in the corners and when braking. And on the climbs, low pressure will help you avoid spinning out on steep/loose pitches. Sure, you can take a running start at a climb if the hill isn’t too long, but once you lose momentum and start to spin, all bets are off. No matter how you look at it, getting off your bike and walking is slower than riding.
And second, lower mountain bike tire pressure improves contact with the surface you’re riding on the same way that suspension does. And that’s true for both climbing and descending. Lower pressure allows the tire to conform better to trail features such as rocks and roots. As a result, the tire can roll over and even around trail features, rather than bouncing from one to the other. It’s hard to stay focused when your teeth are chattering through a descent, or you lose focus on a technical climb because you’re being bounced between roots and rocks.
More energy means more speed
Low tire pressure helps conserve energy for the same reasons it helps increase speed. Improved grip on descents means fewer crashes and less mental fatigue from wondering if your tires will be able to hold their line through the next corner or down the next steep loose pitch. Likewise, on the climbs⎯ not only is getting off your bike, walking for a while, and then getting back on slow, it uses up a lot more energy than simply taking a few extra pedal strokes.
On top of reducing fatigue by conforming better to trail features and increasing grip, low tire pressure also reduces vibration. Vibration emanating up from the ground through your tires and bike and into your body may sound inconsequential, but it isn’t. That vibration increases muscle friction, which produces heat. The friction and heat is wasted energy, and over the course of an entire day of riding it can add up, possibly cutting that day’s ride short, or even making you more tired for tomorrow’s adventures.
All in all, less wasted energy means you have more left over to power up climbs or charge through descents! And as we’ve seen, you’ll also be much more efficient and able to cover more ground in a day. That means more riding for the same amount of effort.
Low pressure has its limits
I refer to the pressures I talk about here as low, but they’re only considered low because they’re lower than what used to be considered the norm. Back when most people used tubes in their mountain bike tires, pressures were higher out of necessity. Low tire pressures still had the same advantages before the advent of tubeless tires in that they could conform more easily to the terrain, but that also meant that it was easier to pinch the tube between the rim and the tire, causing a flat.
Today, thanks to tubeless tires, lower pressures are commonplace, but there’s still a limit to how low they can go. At a certain point, pressure that is too low will cause a tire to become unstable and even cause rim damage. For example, a tire can fold over while cornering if there isn’t enough pressure, causing instability and possibly a crash. Or, a hard hit on a rock or other protrusion can cause the tire to conform too much and damage the rim if there isn’t enough of an air cushion in between the two.
Once you find the tire pressure that works best for you, you’ll need to check your tires often to make sure they stay there. The Topeak D2 SmartGauge takes precise pressure measurements and is small enough to carry with you on a ride.
Experimentation is key
In closing, there are a lot of variables that go into choosing the right tire pressure. Nobody can tell you exactly what pressure is best for you as there are too many variables that are unique to each rider: weight, tire size, riding style and terrain, to name a few. Experimentation is key. The more you ride, the more you’ll get to know what pressure works best for you.
Now it’s your turn!
If you have any questions or comments, please leave them in the comments section below, or you can contact me directly from our Contact page.
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