A large portion of modern mountain bike suspension uses an air spring as opposed to a coil spring. An air spring is lighter and can be adjusted easier than a coil spring. From rear shocks to forks and even some dropper seat posts, there are multiple key features on a bike that use an air spring. To adjust these air springs, a suspension specific shock pump must be used. A standard floor pump will not work. Whether you are setting up your bike’s suspension for the first time, or performing some trail side adjustments, shock pumps are always got to have around.
A shock pumps threads onto the air valve of a fork or shock. If you are pumping up the component for the first time, it’s going to take a lot of pumps to get it up to proper pressure. Shock pumps are designed for precise and high-pressure air flow, so they have a very small air chamber. Once you have the suspension set to the suggested pressure, you can sit on the bike and check your sag. Sag is the amount of travel the shock or fork goes into when you’re on the bike. Sag should usually be set between 25% and 30% of the overall travel. You can adjust the shock or fork by adding or releasing air until your sag is correct. If you are letting air out of the shock, it is better to release it through the shock pump instead of releasing it through the exposed valve. It is typical for a rear shock to have a much higher PSI rating than a fork. A rear shock has a much higher leverage ratio working against it than a fork does. A standard fork usually has anywhere from 50 to 150 PSI in it. A standard rear shock has anywhere from 150 to 300 PSI in it. The lighter a rider is, the less PSI they will need in their suspension.
On most air springs, volume reducing spacers can be internally added to increase the progressiveness of the suspension curve. A progressive curve means that the suspension will act supple at the top of the travel and get stiffer as the fork or shock goes deeper into the travel.
If you have any questions about shock pumps, hop on a call or a chat with one of our expert Gear Advisors today at 888-880-3811. They are always happy to help you with any questions you may have.