One of the first things that a cyclist needs to learn is the importance of setting tire pressure in mountain bikes. A tire that is correctly inflated gives the cyclist control and makes the ride smooth. Low pressure, in contrast, increases the danger of getting a flat tire and makes cycling harder, while high pressure makes the bike bumpy and uncontrollable.
The tire pressure varies according to the condition of the tire, the personal preferences of the rider, the condition of the mountain trail and the type of terrain. You can regulate the tire pressure by buying a good quality bicycle pump. You also need an accurate gauge to take the pressure readings.
Now, you can inflate the tire as per the manufacturer’s specifications and see how the bicycle runs. You can then adjust accordingly. Ideally, you should use the same gauge and pump, because different gauges will give you different readings.
A good strategy is to start with a higher pressure, which means 40-50 psi (3-3.5 bar), and then lower the pressure to find out which pressure suits your bike most. You should also use higher pressure if you are on the heavier side.
The best way to determine tire pressure is to take a test ride. Observe the tire behavior, how it runs on the dirt track, how it slides on the mountain, how it hooks up in corners. If the pressure is more, drop it by 5psi in each tire. If the new pressure compares well, is more stable and the grip on the ground has improved, then you should make it the standard pressure. Otherwise, drop the pressure marginally and rerun the test.
To find the lowest pressure, observe how you can ride without getting flat tires. A tire flattens when the tire compresses against some object and the tube gets damaged.
If the system is tubeless, it is advisable to use lower pressure, say 30 to 40 psi. In tubeless tires, the risk of pinch flats is less and even an occasional rim contact is not alarming. So you can run on much lower pressures. Just be careful that you do not dent the rims or burp air out along the bead. When you are on too low pressure the tire will roll under the rim during hard cornering.
Another balancing test is to watch for rolling resistance with lower pressure. The extra rolling resistance requires extra efforts but it gives increased control and climbing traction. For cross-country racers better efficiency is important than better control.
Squeezing the tire with hand gives the feel of the pressure and is a common method to determine the air requirement.