A couple of decades ago it was unthinkable to see an air spring on a mountain bike, but today air forks and rear shocks are very common and often preferred to the coil options for their lighter weight.
To adjust and maintain the settings of an air shock one needs a high-pressure pump sold at most bike shops.
But since air shocks rely on a common Schrader valve found on most tire pumps, many people wonder whether they even need a specialized shock pump for their mountain bike.
The answer is yes. A special shock pump is needed for properly adjusting an air shock. Unlike regular tire pumps, shock pumps are an instrument of precision. They inject a tiny amount of air into the chamber of a shock and increase the pressure to very high levels.
A regular tire pump cannot complete this task. It will be inaccurate and will prevent you from adjusting the shock properly. Also, tire pumps stress the internals of the shock needlessly.
What Is the Job of a Shock Pump?
The function of a shock pump is to fill the air chamber of a shock to a pressure corresponding to the rider’s weight, preferences, and the terrain.
Shock pumps have the following characteristics:
Low volume. Shock pumps are engineered to move little air because the air chambers of bicycle suspension systems are small and operate at high pressure.
Precision. All shock pumps come with measuring gauges showing the pressure of the shock in pounds per square inch (PSI). Without the feedback provided by the gauge, it would be impossible to accurately adjust the tension.
Small size. Shock pumps are compact and can easily fit in a backpack.
A hose. For extra convenience, shock pumps have fairly long hoses.
Why Can’t a Regular Pump Replace a Shock Pump?
A tire pump cannot replace one built for suspension for the following reasons:
Too much volume
A track pump or even a mini-pump designed for everyday carry moves significantly more air than a shock pump. This property makes it inaccurate and dangerous to the seals of the air chamber.
Lack of precision
A regular pump completely prevents the rider from accurately setting a shock because it transfers a lot of air and doesn’t have the bleed valve found on shock pumps.
The bleed valve allows users to fine-tune the shock’s settings by incrementally removing air.
The air chambers found in suspension forks and rear shocks are tiny. As a result, a small leak can have a great impact on the overall pressure.
For that reason, shock pumps use a screw-down attachment system which creates an airtight seal before the valve of the shock is even opened.
As a result, there’s no air loss when inflating the shock. The same level of control cannot be achieved with a regular clamp-on floor pump.
Are Shock Pumps Expensive?
Not really. A good pump can be had for about USD 20. That’s how much I paid for mine, and it’s been working just fine for a couple of years.
Below is a table with shock pumps averaging between USD 20 and 35.
|Airbone Shock Pump ZT-802||USD 22|
|PRO Performance Suspension Pump||USD 29|
|Procraft Blow Up II Suspension Fork Pump||USD 30|
|GIYO High-Pressure Shock Pump||USD 27|
|Fox High-Pressure Shock Pump||USD 34|
|Beto Bike Tire/Shock Pump MTB||USD 35|
Frequently Asked Questions
If shock pumps are airtight why do I hear a hiss upon removing the head of the pump from the valve of the shock?
The hissing sound does not come from the shock but the pump. When the pump is connected to the valve, air from the shock’s air chamber goes into the pump and stays there until the pump is disconnected. Then, after unscrewing the chuck, the air leaves the pump and produces a sound.
The same phenomenon causes loss of air pressure in the shock upon connecting the pump.
For example, if you pump a shock to 100 PSI, remove the pump, and then connect it again, some air transfers from the shock into the pump and lowers the reading by about 5-10 PSI.
Technically, no air is lost. It’s just “redistributed”.
How often do I have to pump a shock?
Shocks lose air significantly slower than tires. Therefore, upon finding the right settings for you, you won’t have to pump the suspension for weeks if not months.
Having said that, regular checks of the pressure are helpful, especially if the bicycle is stressed consistently.
I realize that shock pumps are necessary and helpful but don’t want to spend money on them right now. Any options?
You can periodically go to your local bike shop and borrow their shock pump for a couple of minutes. If they care about their clients ever so slightly, they’ll let you use it for free. In some cases, the mechanic may even do the adjustments for you.
This method can work for a long time because healthy shocks lose air slowly. However, in the long run, it would be a lot more convenient to have a shock pump on hand.
Tip: Check your local websites for second-hand goods. Chances are somebody is selling a shock pump for half its retail price.
Do dropper posts require a shock pump?
Yes. Dropper posts operating with air also need a shock pump for similar reasons. Hence why a shock pump is such a valuable investment for mountain bikers.
What should I look for when buying a suspension pump?
Most shock pumps on the market are pretty similar. If you buy one from a reputable brand, you’ll be just fine.
I’d advise you to stay away from shock pumps with a small and difficult to read gauges. They may work sufficiently well, but the small display makes them inconvenient.
Can I inflate the tires of my bicycle with a shock pump?
In theory, you could, but it may take you over an hour and a few thousand strokes to accomplish that task because shock pumps move little air.
In consequence, this practice would be justifiable only if you’re in an extreme situation.
E.g., Stuck with a flat tire in the middle of nowhere with nothing but a shock pump because you’d mistaken it for your actual emergency pump.
Furthermore, a regular shock pump cannot operate with a Presta valve and will require an adapter.
Note: Some pumps such as Beto Bike Tire/Shock Pump MTB work in two modes (high pressure + small volume & low pressure + high volume). Similar pumps can inflate both a shock and a tire.
Is it necessary to carry a shock pump when hitting the trails?
A shock pump in your kit may be useful if you’re going on a long tour and your bicycle has air suspension.
Nonetheless, it’s not “ultra-necessary” to transport a shock pump to daily practice sessions as it’s rather hard for a suspension to lose air in a short period.
But if you’re still fine-tuning the settings of your shocks, it would be wise to bring a shock pump with you until you’ve reached the desired performance.
If you insist on covering all angles, you could invest in the aforementioned dual (shock + tire) pumps and replace your current emergency tire pump with one.
Tip: If you’re riding in a group, you could have a designated shock pump carrier who rotates every time. This way the entire crew would have access to a shock pump in case of emergency.
Can I ride my bike if my suspension has no air in it?
It’s not recommended. An air shock without air in it could easily be damaged as it will be bottoming out, especially if the terrain is harsh.
Riding like that could break the internal mechanism of the shock because the internals would be clashing against each other.
Moreover, the geometry of the bicycle would be affected too.
Note: The frame could be damaged too.
How accurate are the gauges of shock pumps?
Cheaper/consumer shock pumps are not incredibly accurate. The displayed numbers could deviate by +/- 10 PSI from reality.
More often than not, that’s good enough for most of us. It would be hard to justify the extra money that one would have to spend on a super-accurate shock pump.
The feel and consistency matter the most. For example, if you know that your shock performs well when set at 95 PSI with the particular pump that you have, then it wouldn’t matter if the real number is 85 or 105 PSI as long as you rely on the same pump.
If you happen to switch pumps, you’d just have to find the number produced by that pump that corresponds to your desired settings.
Truth be told, most people wouldn’t need such precise measuring. That kind of fine-tuning is saved for more skilled riders.
How durable are shock pumps?
Quality shock pumps should last years. After all, they aren’t used that often and stay home most of the time.
Some pros replace their pumps frequently, however, because the components wear out and affect the final readings.