Getting your bike’s suspension dialed in makes a huge difference in comfort and control. A key part of that setup is knowing how much air to put in bike shocks. This guide will walk you through the simple steps to find your perfect pressure.
Air pressure is the main adjustment for modern mountain bike forks and rear shocks. It determines how your suspension reacts to bumps and supports your weight. Too little air, and you’ll use all the travel too easily, feeling sluggish. Too much air, and the ride becomes harsh and bumpy.
How Much Air To Put In Bike Shocks
This is your starting point. The correct air pressure for your shocks is primarily based on your riding weight. This isn’t just your body weight—it includes all the gear you wear and carry.
Step 1: Determine Your Correct Riding Weight
Grab a scale and weigh yourself in full riding kit. Be sure to include:
- Your helmet and shoes.
- Your hydration pack or backpack (full of water).
- Any tools or spare parts you normally carry.
This total number is your riding weight. Write it down, as you’ll need it for the next step.
Step 2: Find Your Bike’s Sag Recommendation
Sag is how much your suspension compresses under your static weight. It’s a percentage of the total travel. Most manufacturers recomend a specific sag range, usually between 20-30% for forks and 25-35% for rear shocks.
- Check your shock or fork’s manufacturer website.
- Look in your bike’s user manual.
- Sometimes the recommended range is printed right on the shock itself.
Step 3: Use the Manufacturer’s Chart or App
Nearly every suspension brand provides a baseline pressure chart. You’ll find these online or in the manual. Input your riding weight, and it gives you a suggested PSI (pounds per square inch) or BAR. This is your starting pressure.
Many brands, like RockShox and Fox, also have smartphone apps. These apps offer tailored setup guides based on your specific shock model and weight. They’re incredibly helpful for getting that initial setting.
Step 4: Setting and Measuring Sag
Now it’s time to put air in your shock and check the sag. You’ll need a shock pump, which has a precise gauge. Normal tire pumps won’t work.
- Release all air from your shock by pressing the pump’s bleed valve.
- Attach the shock pump firmly.
- Add air in small bursts until you reach the PSI from the chart.
- Get on your bike gently, wearing all your gear, and assume your normal riding position. Have a friend help or lean against a wall.
- Carefully get off without bouncing the bike.
Next, measure the sag. Most shocks have a rubber O-ring on the stanchion. Push it up to the shock seal before you get on. After you get off, the O-ring shows how far the shock compressed. Use a ruler to measure this distance.
Calculate the sag percentage: (Sag Measurement / Total Travel) x 100. If your fork has 150mm of travel and you measured 30mm of sag, you have 20% sag. Compare this to your target range.
Step 5: Fine-Tuning for Feel
The chart gives you a baseline, but you might need to adjust. Your personal preference and terrain matter alot.
- If you use too much travel too easily, add 5-10 PSI.
- If the ride feels harsh and isn’t absorbing small bumps, remove 5-10 PSI.
- Make small changes, then go for a test ride on a familiar trail.
Remember, rear shocks often require a different pressure than the fork, even for the same rider. Always set them separately using there own charts.
Considering Rider Style and Terrain
A aggressive downhill rider might run slightly higher pressure for support on big hits. A cross-country rider on smooth trails might run lower pressure for comfort. Rocky, technical terrain often benefits from a slightly softer setup than fast, flowy trails.
The Role of Volume Spacers
Volume spacers (or tokens) change the air spring’s progression. They don’t change the initial sag point much. Adding spacers makes the shock feel more supportive deeper in its travel, preventing it from bottoming out easily. If you find you’re bottoming out hard even with correct sag, consider adding a spacer instead of just adding more air, which can make the initial stroke harsh.
Step 6: Regular Maintenance Checks
Air pressure can decrease over time. Get in the habit of checking your shock pressure regularly, like before a big ride. Temperature changes can also effect pressure; air compresses when cold and expands when hot. A shock that felt perfect in the summer might feel too firm on a cold winter morning.
Common Mistakes to Avoid
- Guessing your weight or pressure.
- Using a tire pump instead of a high-quality shock pump.
- Making huge pressure adjustments all at once.
- Forgetting to factor in your gear weight.
- Setting pressure without then checking the actual sag.
- Neglecting to check pressure for months at a time.
Front Fork vs. Rear Shock Setup
While the process is similar, your fork and rear shock are tuned independently. Your fork typically handles more of the impact from roots and rocks, so its feel is crucial for steering control. The rear shock manages pedaling forces and bigger bumps. Don’t be surprised if they end up with different sag percentages.
FAQ: Your Bike Shock Pressure Questions
How often should I check my shock air pressure?
You should check it before every major ride. Small leaks are common, and temperature shifts change pressure. A quick check with your pump takes just a minute and ensures consistent performance.
What if my shock doesn’t have a recommended pressure chart?
If you can’t find a chart, start with a general rule of thumb: for many trail bikes, try 1 PSI per pound of riding weight for the rear shock. For the fork, start at about 0.9 PSI per pound. This is just a rough starting point—setting sag is still essential.
Can I use a regular pump for my bike shocks?
No, you cannot use a regular tire pump. Shock pumps are designed to move very small volumes of air at high pressures with a precise gauge. A tire pump’s gauge isn’t accurate enough for the fine adjustments suspension needs.
Why does my shock feel harsh even with correct sag?
Correct sag is only one part. The harshness might be from too many volume spacers, or your compression damping settings might be too high. Also, check that you haven’t over-inflated the shock trying to prevent bottoming out. Rebound damping that’s too slow can also make a shock feel packed down and harsh.
What’s the difference between PSI and BAR?
PSI (pounds per square inch) and BAR are both units of pressure. 1 BAR is approximately equal to 14.5 PSI. Most shock pumps show both scales. Just be consistent with which unit you use when setting your pressure.
Should my front and rear shock have the same pressure?
Almost never. The front fork and rear shock are different sizes and support weight differently. They will almost always require different air pressures to achieve there recommended sag percentages. Always set them according to their own guidelines.
How does temperature affect my shock pressure?
Air expands when hot and contracts when cold. If you set your pressure in a warm garage and then ride in freezing weather, your pressure will be lower and the shock will feel softer. The reverse is true in summer heat. Try to set your pressure in conditions close to your riding temperature.
Finding the right air pressure is the foundation of great suspension performance. It takes a little time to get it just right, but the improvement in your ride is instantly noticeable. Start with your accurate riding weight, use the manufacturer’s chart, set your sag, and then fine-tune from there based on your feel on the trail. With these steps, you’ll have your bike handling exactly how you want it.