How often should you check your fork and shock absorber pressure?

It is recommended to check the pressure with a special high-pressure pump before each serious trip to the mountains or at least once a month with regular skiing. The air may leak a little through the seals over time.

Is it possible to inflate a fork with a regular car compressor?

Absolutely not. Bicycle suspension air chambers have a very small volume, but require high pressure (often more than 100-200 PSI). A regular compressor can instantly damage the insides of the shock absorber. Use only a specialized fork pump (Shock Pump).

What to do if the suspension breaks even with the correct sag?

If the sag is set on the calculator, but the suspension goes all the way through on hard impacts, you will need to add air spacers to the chamber. This will make the suspension feel more progressive at the end of the stroke.

Dual-gimbal suspension setup

Calculation of pressure (PSI) and sag (Sag) for mountain MTB bikes (27.5" and 29")

Your weight with equipment (kg)

Skating style

Fork travel (mm)

Amortization rod stroke*

*Stroke is indicated on the rearmost shock absorber (for example, 210x50).

Enter your gear weight (helmet, backpack, water)
to get basic suspension settings

Recommended settings:

Front fork 0 PSI

Sag: 20% Drawdown: 0 mm

Rear shock absorber 0 PSI

Sag: 25% Drawdown: 0 mm

ℹ️ These are average starting values for air springs. Pressure may vary depending on frame geometry (leverage) and fork brand (RockShox, Fox, etc.). Make fine adjustments using the elastic band of the sag.

Suspension Tuning Calculator: Calculate Pressure (PSI) and Sag

Buying an expensive mountain bike does not guarantee a soft ride. If the air fork and rear shock are not adjusted to your weight, the bike will behave unpredictably: it will either bounce off every stone like a hard log, or “break through” until the metal rings on the slightest bumps. For the suspension to work correctly, it must be inflated to a certain pressure.

We have developed an online calculator especially for this purpose. It will help you find out the base pressure (PSI) values and the correct sag for the front and rear shock absorbers in a couple of seconds.

How does the suspension calculator work?

The tool uses average factory coefficients from leading fork and frame manufacturers. To get an accurate calculation, you need to specify only a few parameters:

Your actual weight. Important: indicate your weight in full equipment! A helmet, protection, backpack with tools and a water bottle can easily add 3-5 kilograms to your “net” weight.
Riding style For cross-country (XC), the suspension is pumped harder so as not to lose energy when pedaling. For enduro and aggressive descents, they make it softer - so that the wheels literally “stick” to the terrain.
Suspension travel Specify the front fork travel (for example, 140 mm). For the rear shock absorber, you need to indicate not the travel of the frame wheel, but precisely the rod travel of the shock absorber itself (usually written on its body, the second number in size, for example 210x50).

What is Sag and why measure it?

The calculator displays not only the pressure in PSI, but also the Sag value in millimeters and percentage. Sag is how much the suspension sags simply under the weight of your body when you carefully sit on the bike and take a working stance (without jumping on the pedals).

This is the most important setting parameter. Why is it needed? When you are driving on a flat road and the wheel hits a hole, the fork mustuncleandown so that the wheel does not hang in the air, but maintains traction with the ground. It is this unclamping power reserve that Sag provides. Typically it ranges from 15% to 30% of the total shock absorber travel.

Tips for setting up after calculations

The data from our calculator is the perfect starting point. If you are just starting to get into extreme sports or have decided to buy a modern 27.5 dual suspension bicycle, setting the air correctly is the first thing you need to do before going out on the trail.
To inflate the suspensionyou definitely need a special high-pressure fork pump. A regular wheel pump or car compressor will not work - the air chambers of a bicycle have too small a volume, and with a regular pump you either won’t pump anything or will instantly squeeze out the seals with high pressure.

Pump up the PSI values that the tool gave, slide the rubber ring (O-ring) on the fork leg down to the boot, carefully sit on the bike and get off just as smoothly. If the ring has moved exactly by the millimeters indicated in the calculator, your suspension is set up perfectly!