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4 Common Reasons Your MTB Shock is Losing Air

4 Common Reasons your shock is losing air

You’ll hear this a lot from MTB and eMTB riders: my shock (or fork) is losing air. Every time I check it it’s lower than I left it.

Well there are a few reasons that a functioning shock will show lower PSI.

Are you Pre-Charging your Pump?

The most common is not pre-charging the pump line prior threading the pump on and opening the Schrader valve.

This one is pretty easy to explain – the gauge is located at the end of a volume of hose. If you do not pre-charge that hose to approximately what you have in the shock when you open the Schrader valve to your air spring you increase the volume of the main chamber which will lower the overall PSI.

The smaller the suspension’s main chamber the more dramatic the PSI drop will be.

That’s why it’s a good idea to pre-charge your suspension pump. Thread the pump on until it makes a seal with the shock but hasn’t yet opened the valve.

Charge the pump to approximately what is in the main chamber.

Finish threading the pump onto the fork or shock. It will show a more accurate pressure of the main air spring as it doesn’t have the volume loss as a non-charged pump.

Like I mentioned this is the most common cause for “air loss” in suspension. It is seen in both the fork and rear shock.

Did You Cycle the Shock and Charge the Negative Air Chamber?

Another common cause for lower pressure, particularly in rear shocks, is setting the pressure and not charging the negative air chamber.

This is typically seen when large PSI jumps are made in the shock such as a brand new piece of equipment.

What does it look like? You set the pressure to the suggested PSI. You jump on the bike and go ride. Bike feels soft. You check the air and it’s dropped from the beginning of your pedal.

Unlike most forks, which usually charge the negative air chamber at full extension and thus see less of this, your rear shock most likely has an air divot to charge the negative chamber somewhere a bit into the stroke.

That means it takes a few compressions of the suspension to engage the negative air chamber. And once the piston allows the negative air chamber to fill it effectively drops the volume of the main chamber. Then when the shock extends and you check the PSI it will be lower.

It is a good practice to give a rear shock a few bounces during setup, especially when large PSI changes are made to ensure that the negative air chamber has charged and the shock will have the support you expect.

Does it Need Seals? Or Just Had Seals Installed?

It is actually more rare for a shock to be truly bleeding off PSI than for one of the above two to be the culprit on new suspension.

As the suspension ages seals may degrade and can be the cause of air loss. Suspension manufacturers have suggested service intervals based on hours of operation, but if your more aggressive on your equipment, such as a racer, you may find that shortening the service window keeps your bike running smoothly.

Some common causes of premature seal wear include dirt ingress, which is why it is so important to keep your stanchions as clean as you can before each ride. The less dirt the suspension pulls into the seals the less abuse on the seals, shafts, etc is incurred.

Occasionally a recently serviced fork or shock may ‘roll’ a seal or have been nicked during installation. Typically you’ll find this out when you’re setting back up for your ride or on your first ride. This is very rare on a professional level as the quality control of parts and service techniques eliminates the chance for most of this. But, there’s typically a handful of small to medium seals which make create an air-tight chamber and if one of them isn’t working you might have a slow leak.

Dirty or loose Schrader valves can cause air loss, although most shocks have a decently sealed cap these days.

Extreme temperature or altitude changes will effect your PSI and should be accommodated for. Check your sag before your chair lift day at altitude!

A less common cause, but it is out there: chemical degradation. Seal materials are susceptible to being attacked by other chemicals – so be aware of what comes in contact with your suspension.

A typical way to test for faulty seals is to set the shock at a test pressure, say 100psi, and allow it to sit overnight. Pre-charge a pump and check the pressure. A notable drop, ie more than might be expected from the pump increasing the main chamber volume, is likely worth an additional look.

Another test, although I must disclaim this one a bit, is to submerge the shock and watch for bubbles. I try to avoid this option as much as possible personally as I find it has to be a pretty decent leak for me it to be losing air visibly and can tend to be detected using the overnight pressure test. If it is leaking and pulls water in you’re going to have remove the water and any contaminated oil or grease since you don’t want water diluting or boiling in your suspension’s air chamber.

Very Rare PSI Loss Causes

The least common cause of air loss would be a crack or micro-crack in a casting. This can be a hard one to determine, particularly as it may require the shock to cycle and load up before the pressure rises enough to “open” the crack and vent air pressure.

Occasionally seals will have a similar end of service life where the air loss is occurring as the PSI increases, but, it’s fairly uncommon.


In conclusion, most of the air loss attributed to new or newly serviced product can be traced back to the pump increasing the volume, and thus lowering the pressure or in the case of rear shocks the negative air chamber charging.

If you’re using good practices with your setup and still noting air loss the next step is most likely to do a seal service, especially if the shock is near the service window or if its’ been used in extreme conditions.

If the new seals aren’t helping it’s probably worth digging a little deeper and possibly using a professional resource to help you locate the issue.

Local or ride in the South Orange County area? Come by and have our team service or tune your suspension. We are located at 21098 Bake Parkway #112 in Lake Forest near the corner of Bake and Trabuco.

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Pro Tune Suspension for Specialized

BikeCo Pro Tune Specialized Enduro or Stumpjumper

Pro Tune Suspension for Specialized Enduro & Stumpjumper

Specialized Enduro Pro Tune Suspension

We are excited to offer BikeCo Pro Tunes for the Specialized Enduro & Stumpjumpers equipped with FOX suspension. Pro Tune Suspension for Specialized bikes will take your bike’s performance to the next level.

After extensive testing our range of Specialized Pro Tunes will narrow the FOX performance window to your riding specifics. Depending on your size, riding style, terrain and ground speeds our team will create a profile to fine tune your FOX shock.

With proprietary lubes, custom design shim profiles and our unique (very thorough) bleeds your Enduro or Stumpjumper rear shock will have improved small bump compliance, heat resistance, bottom out and support. Each click of rebound and compression will be a more finite adjustment allowing more precise setup whether you’re riding your local loop, an epic trip or a weekend’s race.

BikeCo Pro Tunes bring out the ultimate performance across a growing range of brands. Specialized is the latest addition to suspension designs such as VPP, DW, Switch Infinity and more. With each design our tunes are modified dependent on leverage ratios, bike lengths, chainstay lengths and stock shock designs.

With so many controls on modern shocks it’s easy to be confused when working to improve a single aspect. Pro Tune clients have access to our team to help with initial setup as well as advice for changes to your suspension as your riding develops.

Compression, rebound, volume spacing and PSI balance compliance, support and feel. Why not have access to Joe Binatena and our team of suspension tuners to dial in your bike?

Pro Tune Specialized Enduro and Stumpjumper

Common Issues for Stock Suspension

Stock shocks have to work for a wide range of riders. Weight, aggression and ground speed variations mean stock suspension is asked to be something for everything. There are a handful of typical issues BikeCo Pro Tunes address.

Compliance. Lighter riders often find bikes over compressed with poor small bump compliance. These are similiar issues for riders on the slower or medium ground speed ranges as the bike doesn’t build up the necessary momentum to really activate the dampers.

Support. Tied to issues with compliance for many riders. In order to improve compliance it’s common to run a lower PSI. However this increases your sag percentage which decreases support, top out and ramp rate.

Heat Resistance. Our proprietary lubes are designed maximize the balance between heat resistance and fluid flow dependent on ground speed and rider weight. Our bleed quality reduces air ingress to the oil which provides better performance with less variation between the beginning of your descent and the end.

Specialized Pro Tunes

Pro Tune Suspension for Specialized

Your Specialized Enduro or Stumpjumper’s performance can be taken to a whole other level with BikeCo Pro Tunes. Dialing in the rear shock, fork as well as cockpit and wheels are common upgrades for Specialized riders here at

Understanding your Specialized Enduro or Stumpjumper’s setup will increase your riding enjoyment and improve your learning curve. With our Pro Tunes and follow up services we will help take your Specialized from “pretty good” to “oh man, this is dialed!”

Ready to take your Enduro or Stumpjumper to the next level? Reach out to our team to start the process today:

Pro Tune Input

Want to learn more about how BikeCo Pro Tunes benefit riders from Novices to Racers? You know what, before we get you that link let’s touch on something:

We named this service Pro Tune Suspension, but an argument could be made that the earlier you are in your riding journey the MORE that Pro Tuned suspension will help. Why learn or master skills to compensate for poorly setup or poor handling suspension when you could have your bike dialed in by the experts and work to learn proper skills and techniques?

Learn more about the benefits across the board on Pro Tune Suspension here.

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BikeCo Service Evaluation

Service Evaluation Vimeo Thumb

BikeCo Service Evaluation

When you bring your bike in for service BikeCo’s staff will go through your bike front to back. This pre-service evaluation provides an overview of basic maintenance your bike requires.

Do you have addition concerns or hard to diagnose issues? No problem. Let our team know and they will note your issues for our mechanics.


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BikeCo Full and Partial Fork Services

Full and Partial Fork Services by

BikeCo Full and Partial Fork Services

For the best performance it is important to properly service MTB suspension. BikeCo Full and Partial Fork Services provide 3 options to keep suspension riding at its best.

Partial Fork Service from $40, Full Fork Service Level A from $125 and Full Fork Service Level B from $175.


These services maintain both standard and Pro Tune forks. Running a stock fork? Learn more about advantages of BikeCo Pro Tunes here.

Service interval recommendations are based upon mileage, riding conditions, riding style as well as preference.

BikeCo’s staff will help you define which service is best for your needs at time of drop off (for local clients) or over the phone for suspension shipped in. Continue reading BikeCo Full and Partial Fork Services

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Purpose Built Wheels by

Purpose Built Wheels by

Purpose Built Wheels by BikeCo Joe Binatena

Purpose Built Wheels by

Improve trail tracking and performance with Purpose Built Wheels by

It’s possible to calculate the performance of your mountain bike wheels. To start look at the sum of the major parts. Hubs, Spokes, Rims. Then factor in the builder’s skill in assembly as well as tuning. Yes, wheel tuning is a thing – more on that later. Continue reading Purpose Built Wheels by

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BikeCo Frame Prep

BikeCo Frame Prep on Ibis

Tracy Ibis Build HD4 rectangle

BikeCo Frame Prep

Build integrity for your new mountain bike starts before you hang any bits on the frame. In fact, for the ultimate performance and longevity BikeCo developed specific MTB Frame Prep procedures.

Pivots, Bearings, Axles, , Hangers, Bottom Brackets and Headsets are addressed in BikeCo’s MTB Frame Prep services. BikeCo Frame Prep services ensure maximum service life, ultimate trail personality as well as quiet performance for your mountain bike.

Like the BikeCo Pro Tune Suspension originally Frame Prep service was only available for race bikes. Over the years BikeCo’s team developed mtb frame prep procedures to address issues that average riders encounter.

We stand behind our Frame Prep service for 1 year. Should your frame develop noise or issues from components associated with Frame Prep BikeCo will take care of you. Continue reading BikeCo Frame Prep

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BikeCo Service Rates

BikeCo Service Rates Online Service Rates

The Bike Company offers a complete service lineup for MTB, Road, Hybrids and some electric bicycles. warranties all service for at least 30 days.
Suspension rebuilds are warrantied for 90 days.
BikeCo Frame Prep is warrantied for 1 year.

Typically, BikeCo matches manufacturer service warranty periods. Ask for more details as needed.

Questions on a recent service? No problem, give our team a buzz and they will dial you in.

Scroll through for more details. Continue reading BikeCo Service Rates

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BikeCo Pro Tune Suspension Advantages

BikeCo Pro Tune Advantages

BikeCo Pro Tune Suspension Advantages for Novice, Experienced Riders & Racers

BikeCo Pro Tune Suspension Advantages

For years we’ve has been providing riders access to the best performing Fox Suspension through our proprietary Pro Tunes designed by owner Joe Binatena. BikeCo Pro Tune Suspension is designed to maximize damper performance to your riding specifics.


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