MTB Suspension Tools
RockShox Suspension Calculator
This RockShox Suspension Calculator helps you find a great starting point for your fork’s air pressure and rebound settings. Input your weight, suspension travel, and desired sag to get personalized recommendations.
Visualization of your desired sag relative to total suspension travel.
| Riding Style | Typical Sag % | Feel |
|---|---|---|
| Cross-Country (XC) | 15-20% | Firm, responsive, and efficient for climbing. |
| Trail / All-Mountain | 20-30% | Balanced for all-around performance, good compliance and support. |
| Enduro / Downhill | 25-35% | Plush and forgiving for maximum traction and big-hit absorption. |
General starting sag recommendations based on riding discipline.
What is a RockShox Suspension Calculator?
A RockShox Suspension Calculator is a specialized tool designed to simplify one of the most critical aspects of mountain bike setup: suspension tuning. Instead of relying on guesswork, this calculator uses your specific inputs—primarily rider weight, suspension travel, and desired sag—to provide a reliable starting point for air pressure and rebound settings. The goal of any good RockShox Suspension Calculator is to help you achieve a balanced ride that offers both support and sensitivity on the trail. Proper setup is essential for maximizing traction, control, and confidence.
This tool is for any mountain biker with a RockShox air-sprung fork or rear shock. Whether you’re a beginner trying to understand your new bike or an experienced rider dialing in a new setup, a calculator removes the initial uncertainty. A common misconception is that the numbers from a RockShox Suspension Calculator are absolute. In reality, they are a baseline recommendation. Factors like riding style, typical trail conditions, and personal preference will require you to fine-tune from this excellent starting point.
RockShox Suspension Calculator Formula and Mathematical Explanation
The core of this RockShox Suspension Calculator relies on established principles of suspension setup. The formulas are designed to provide a balanced and predictable starting point.
Step-by-Step Derivation:
- Air Pressure Calculation: The primary factor is rider weight. A common starting point is a near 1:1 ratio of rider weight in pounds to PSI, but this can be aggressive. This calculator uses a slightly more forgiving ratio (`Rider Weight (lbs) * 0.9`) to provide a plusher initial setup, which is often more suitable for a wider range of riders.
- Sag in Millimeters: This is a direct calculation based on your desired sag percentage and total suspension travel. The formula is `Sag (mm) = Total Travel (mm) * (Desired Sag % / 100)`. This tells you how much the suspension should compress under your static weight.
- Rebound Damping Calculation: Rebound is linked to air pressure—higher pressure requires more damping (slower rebound) to control the spring force. This calculator uses a base setting (e.g., 5 clicks from fully closed) and adds 1 click for every 20 PSI over a baseline of 100 PSI. This progressive formula ensures the rebound matches the spring rate. A proper bike setup calculator should always link these two variables.
Variables Table
| Variable | Meaning | Unit | Typical Range |
|---|---|---|---|
| Rider Weight | Total weight of the rider with all gear. | lbs / kg | 100 – 250 lbs |
| Suspension Travel | The total distance the fork or shock can compress. | mm | 100 – 200 mm |
| Desired Sag | The percentage of travel used under static rider weight. | % | 15 – 35% |
| Air Pressure | The primary spring force setting. | PSI | 50 – 200 PSI |
| Rebound Clicks | Damping setting controlling the return speed of the suspension. | clicks from closed | 0 – 18 clicks |
Practical Examples (Real-World Use Cases)
Example 1: Trail Rider
- Inputs: Rider Weight: 190 lbs, Suspension Travel: 140 mm, Desired Sag: 25%
- Calculator Output:
- Air Pressure: ~171 PSI
- Sag in mm: 35.0 mm
- Rebound: ~9 clicks from closed
- Interpretation: This setup is ideal for a trail rider looking for a balance of climbing efficiency and descending capability. The 25% sag provides good small-bump sensitivity without using too much travel on flatter sections. The rebound setting is firm enough to prevent the fork from feeling like a pogo stick on repeated hits. This is a classic use case for a RockShox Suspension Calculator.
Example 2: Lightweight XC Rider
- Inputs: Rider Weight: 135 lbs, Suspension Travel: 120 mm, Desired Sag: 18%
- Calculator Output:
- Air Pressure: ~122 PSI
- Sag in mm: 21.6 mm
- Rebound: ~6 clicks from closed
- Interpretation: This firmer, more efficient setup is tailored for cross-country riding. The 18% sag minimizes pedal bob and keeps the bike in a more aggressive, responsive posture for racing. The lower rebound damping matches the lower air pressure. Our detailed fork pressure guide can provide more context for competitive tuning.
How to Use This RockShox Suspension Calculator
Using this RockShox Suspension Calculator is straightforward. Follow these steps for an accurate initial setup.
- Enter Your Weight: Put on all your typical riding gear (helmet, shoes, hydration pack, etc.) and weigh yourself. Enter this value in the “Rider Weight” field. Accuracy here is key.
- Enter Suspension Travel: Input the total travel of your fork or shock. This can usually be found on the manufacturer’s website or sometimes printed on the suspension itself.
- Select Desired Sag: Use the slider to choose your desired sag percentage. Refer to the helper text and table for guidance based on your primary riding discipline. The calculator updates in real-time.
- Review the Results: The calculator will immediately display the recommended Air Pressure, Sag in mm, and Rebound Setting. This is your starting point. You’ll need a shock pump to apply these settings.
- Apply and Verify: Use a shock pump to set the recommended air pressure. Then, get on your bike and gently cycle the suspension a few times to equalize the air chambers. Reset the O-ring on your stanchion, carefully get into your riding position, and then carefully dismount. Measure the distance the O-ring has moved—this is your actual sag. Adjust air pressure up or down until the measurement matches the “Target Sag” from the calculator. Set your rebound dial to the recommended clicks from the fully closed (slowest) position.
Decision-Making Guidance: If the bike feels too harsh on small bumps, decrease air pressure slightly (add more sag). If you are bottoming out too easily on big hits, increase air pressure (reduce sag). Our guide on MTB suspension tuning provides more advanced tips.
Key Factors That Affect RockShox Suspension Calculator Results
While a RockShox Suspension Calculator provides an excellent baseline, several factors can influence your final ideal settings.
- Riding Style: An aggressive rider who jumps and hits features hard will need more air pressure and slower rebound than a smoother, more grounded rider of the same weight.
- Trail Type: Smooth, flowing trails may allow for a firmer setup (less sag), while steep, chunky, technical terrain often requires a plusher setup (more sag) for traction and control.
- Air Temperature: Air pressure inside your shock can change with ambient temperature. On very hot or cold days, you might need to re-check your pressure.
- Volume Spacers (Tokens): These plastic tokens reduce the air volume inside your fork, making the spring rate more progressive. If you have tokens installed, you can run slightly lower air pressure for better small-bump feel without bottoming out as easily. Learn more by reading about mountain bike suspension setup.
- Bike Geometry: A bike with a slack head tube angle puts less weight on the front fork when seated, which can affect sag measurements compared to a bike with a steeper head tube angle.
- Service Intervals: A freshly serviced fork with clean oil and seals will perform differently than one that is overdue for maintenance. Stick to a regular service schedule to ensure consistency. A visit to our contact-us page can help you schedule a service.
Frequently Asked Questions (FAQ)
This can be due to “stiction” in the seals of a new or unserviced fork, inaccuracies in your shock pump’s gauge, or the specific leverage curve of your bike’s frame (for rear shocks). Always trust the physical measurement over the pump’s gauge. The RockShox Suspension Calculator provides the target; you adjust pressure to meet it.
For the fork, it’s best to be in the “attack position” (standing on the pedals, centered over the bike). For the rear shock, sitting is generally acceptable as it represents the position you’re in for much of your riding, especially climbing. Consistency is most important.
It means you should turn the rebound dial all the way clockwise until it stops (this is the slowest setting, or “closed”). Then, turn it counter-clockwise the recommended number of clicks. This is the standard method for setting rebound damping.
It’s a good practice to check it before every ride. Air pressure can slowly leak over time, and temperature changes can also affect it. A quick check ensures your bike performs consistently.
Always round to the nearest whole number and then test on the trail. Suspension tuning is about feel, not just numbers. A 2-3 PSI difference is a great starting point for experimentation. Don’t be afraid to deviate from the RockShox Suspension Calculator recommendation.
While the principles of sag and weight-to-pressure are similar, this calculator is optimized based on typical RockShox air spring curves. For the most accurate starting point, you should use a calculator specific to your suspension brand if available.
Packing down happens when your rebound is set too slow. The suspension can’t extend fast enough between successive hits, causing it to “pack” deeper into its travel, feeling harsh. If you experience this, speed up your rebound (fewer clicks from closed).
Yes. Because e-bikes are heavier, they often require higher air pressures and slightly slower rebound settings to control the extra mass. When using this RockShox Suspension Calculator for an e-bike, ensure your rider weight is accurate and consider starting with 1-2 extra clicks of rebound damping.