Customers often ask for our recommendation on what tire pressure they should run. For most riders, the key is finding a pressure where you rarely bottom out on your rim, but it does happen on rare occasion. It’s a similar idea to how you would set up your suspension – if you NEVER bottom out, then you are not utilizing the suspension to its potential. Don’t make the mistake of running your pressure so high that you have zero chance of bottoming out your rim. This is detrimental to your traction, and in most cases creates harsher forces for carbon rims to deal with.
There is a point where there is diminished control if the pressure is too high or too low. When tire pressure is too low, you will have a bike that is squirmy when changing direction, and the tires can even fold over during hard cornering. You may develop a sluggish feel due to the increased rolling resistance. Furthermore, running too low a pressure increases the chance of sidewall punctures and excessive rim strikes which can be destructive to your rim. Run too much pressure, and you’ll find yourself bouncing off bumpy terrain, leading to a very skittish feeling bike. Excess pressure will also result in decreased traction, especially when wet or loose.
Once you’ve found your sweet spot, you will still need to understand these five variables and how they will influence your pressure
- Tire Size and Type
- Rim Width and Diameter
- Rider Weight
- Ride Style
Tire Size and Type.
Currently the mountain bike market is in a state of flux with respect to what tire size is ideal. For years, the 2.3″ tire was the “go-to” for trail bike applications. Cross country riders typically found themselves typically running 2.0″ to 2.2″ tires. Acceptance with wider tires came with the surge in popularity of plus bikes which generally used tires 2.8″ and greater. More recently, a new segment of Wide Trail tires which typically sit around 2.5″ have become popular with riders seeking more grip and control on their trail bikes. Regardless of what tire you run, each tire has a different ‘ideal pressure range’
As a rule of thumb, larger tires require less pressure because they have increased air volume. Let’s say you typically run 24 psi in your 27.5″x2.3″ Maxxis Minions. If you put on a 2.8″ Maxxis Rekon on the same rim, you would lower your pressure significantly due to the increased air volume. Conversely, you would increase the air pressure if you put a narrower 2.1″ tire on the same rim. You should also take the tires sidewall casing into consideration. If you change your tire for something of the same type and width but the casing is heavier duty, then you can likely lower your pressure while still maintaining that tires characteristics.
How much the rider weighs also plays a big role in what tire pressure should be run. Heavier riders will always have to run higher pressure than a lighter rider given the same tire and conditions. A 200lb rider may find that 29psi is ideal for their 2.35 Schwalbe Rock Razor, while a 140lb rider may find that running 29psi in the same tire makes it skittish, and uncontrolled due to it being too hard. In which case the solution would be to back off the tire pressure a couple psi at a time until the ideal balance of control and tire support is found.
The amount of gear you ride with must also be taken into account. If you’re going on an 8hr unsupported epic, there’s a good chance you’re carrying a big pack with lots of clothing, tools and amenities. This extra weight will affect the ideal pressure you should run.
*Your bodyweight puts more force on your back wheel compared to your front, so it is common to run ~10% less pressure in the front tire.
Rim Width and Diameter
Wider rims are make tires more stable and the air volume is increased, so you can lower your pressure. Running a larger diameter 29″ rim compared to a 27.5″ with an identical rim will also increase the tire volume. If you are used to running 28psi with your 27.5″ rims, you would likely achieve the same feel by running 25-26psi on the same tires on 29″ rims.
Mountain bike terrain varies significantly based on where you are and what season you’re in. Tire selection and the corresponding pressure required for a wet, soft, greasy trail will be different than a hard packed dry tacky trail.
When conditions get wet and greasy, it is often advantageous to drop a couple psi from your tires. The result is a more supple tire that will have a slightly larger footprint which provides more traction. The decreased pressure also allows the tire to contour to the terrain a little better, giving the tire’s tread a better foothold. Conversely, if the trail conditions are hard packed, tacky and buff, increasing the tire pressure a few psi will lead to slightly decreased rolling resistance (to a point) and increased resistance to rim strikes.
Last but not least, riding style plays a massive role in what sort of pressures you should run. In our experience, ride style falls on a spectrum. On one side we have the calm and calculated rider who is precise and deliberate with line choice. They are ‘surefooted and light’ over rough and technical terrain, with very little skidding and horsing the bike around. On the other side we have the more aggressive rider who ‘makes their own line’ and is often charging through rough and technical terrain. This means plenty of body language, induced skidding, and of course some crashing and bashing that inevitably comes with that ride style. While either technique can be the fastest method down the trail with the right rider, the tire pressure requirements can be vastly different!
If your ride style is more calculated, and controlled, you can likely get away with lower pressures since there is less chance of rim strikes and tire sidewall exposure. Whereas, if you’re exceptionally aggressive, adding pressure will increase the stability in the tires sidewall and reduce the chance of excessively bottoming out the tire on your rims.
We hope this has helped you with the age old question “What pressure should I run?” Should you have further questions, never hesitate to contact us. We’re here to help, and want your ride experience to be the best it possibly can be!