Trek Suspension Calculator
Your expert tool for dialing in the perfect Trek mountain bike suspension settings based on your weight and model.
Suspension Setup Calculator
Enter your total weight including helmet, shoes, and any pack you ride with.
Select your Trek full suspension mountain bike model.
Recommended range is 25-30% for most trail riding. Lower % is firmer, higher % is plusher.
Recommended Rear Shock Air Pressure
— PSI
Suggested Rebound
—
clicks from closed
Target SAG
— %
of shock travel
Setup Style
—
Balanced
Pressure vs. Rider Weight Chart
Model-Specific Starting Points
| Rider Weight (kg) | Fuel EX (PSI / Rebound) | Slash (PSI / Rebound) | Top Fuel (PSI / Rebound) |
|---|---|---|---|
| 55-64 | 130-145 PSI / 8-9 clicks | 140-155 PSI / 7-8 clicks | 120-135 PSI / 9-10 clicks |
| 64-73 | 145-165 PSI / 6-7 clicks | 155-175 PSI / 5-6 clicks | 135-155 PSI / 7-8 clicks |
| 73-82 | 165-185 PSI / 4-5 clicks | 175-195 PSI / 3-4 clicks | 155-175 PSI / 5-6 clicks |
| 82-91 | 185-205 PSI / 2-3 clicks | 195-220 PSI / 1-2 clicks | 175-195 PSI / 3-4 clicks |
| 91-100 | 205-225 PSI / 1-2 clicks | 220-245 PSI / 0-1 clicks | 195-215 PSI / 1-2 clicks |
What is a Trek Suspension Calculator?
A Trek suspension calculator is a specialized tool designed to help riders determine the optimal starting settings for their mountain bike’s front and rear suspension. Unlike generic calculators, a Trek-specific tool considers the unique kinematics and leverage ratios of different Trek models, such as the Fuel EX, Slash, and Remedy. The primary goal is to calculate the recommended air pressure (in PSI) for the shock and fork to achieve a desired percentage of “SAG,” which is the amount the suspension compresses under the rider’s static weight. Using a Trek suspension calculator is the first and most critical step to unlocking the full performance potential of your bike, ensuring better traction, control, and comfort on the trail.
This tool is essential for every owner of a full-suspension Trek mountain bike, from beginners to seasoned experts. A common misconception is that suspension settings are “set and forget.” In reality, they should be adjusted based on rider weight changes, gear, and even the type of terrain. The Trek suspension calculator simplifies this complex process, providing a scientifically-backed starting point that eliminates guesswork and ensures a balanced and responsive ride.
Trek Suspension Formula and Mathematical Explanation
There isn’t a single universal mathematical formula for suspension setup; it’s a complex relationship between rider weight, air volume, and the bike’s leverage ratio. However, the core principle of any Trek suspension calculator is to solve for the air pressure needed to achieve a target SAG.
The process can be broken down:
- SAG Calculation: SAG is the foundation. It’s expressed as a percentage of the total shock stroke. For example, if a shock has a 50mm stroke and you want 30% SAG, the shock should compress 15mm under your static weight.
- Leverage Ratio: This is a critical, model-specific variable. It describes how much the rear wheel moves for every unit the shock compresses. A bike with a 2.5:1 average leverage ratio means the rear wheel moves 2.5mm for every 1mm of shock compression. Enduro bikes like the Slash often have a more progressive leverage curve than XC bikes like the Supercaliber. Our Trek suspension calculator factors this in.
- Air Spring Curve: Air acts as a spring, and its resistance increases as it’s compressed. This is not linear. The calculator uses a model that approximates this curve to relate rider weight (the force) to the required pressure.
| Variable | Meaning | Unit | Typical Range |
|---|---|---|---|
| Rider Weight | Total weight of the rider plus all gear. | kg or lbs | 50 – 115 kg |
| Shock Stroke | The total distance the shock can compress. | mm | 40 – 65 mm |
| SAG | Percentage of shock stroke used under static rider weight. | % | 15% (Firm) – 35% (Plush) |
| Air Pressure | The pressure inside the main air chamber of the shock. | PSI | 100 – 300 PSI |
| Rebound Damping | Controls the speed at which the shock extends after compression. | Clicks from closed | 0 (Slow) – 20 (Fast) |
Practical Examples (Real-World Use Cases)
Example 1: Trail Rider on a Trek Fuel EX
A rider weighs 84kg with all gear. They own a Trek Fuel EX and prefer a balanced setup for general trail riding. They input their data into the Trek suspension calculator, aiming for a 28% SAG.
- Inputs: Weight = 84kg, Model = Fuel EX, Desired SAG = 28%.
- Calculator Output: Recommended Pressure ≈ 188 PSI, Rebound ≈ 4 clicks from closed.
- Interpretation: The rider sets their shock to 188 PSI. After checking SAG, they find it’s very close to the target. The 4-click rebound setting provides a controlled return that prevents the bike from feeling like a pogo stick. For more info on bike maintenance, see our guide to mountain bike maintenance.
Example 2: Enduro Racer on a Trek Slash
An aggressive enduro racer weighs 75kg and rides a Trek Slash. They need a firmer, more supportive setup for high-speed impacts and drops, so they target a 25% SAG.
- Inputs: Weight = 75kg, Model = Slash, Desired SAG = 25%.
- Calculator Output: Recommended Pressure ≈ 185 PSI, Rebound ≈ 6 clicks from closed.
- Interpretation: Even though the rider is lighter than in Example 1, the pressure is similar. This is because the Slash’s leverage ratio and the lower SAG target both demand higher pressure. The rebound is slightly faster to help the wheel track the ground over rapid, successive hits. This is a key insight provided by an accurate Trek suspension calculator.
How to Use This Trek Suspension Calculator
Using this calculator is a simple process to get a great baseline tune.
- Enter Your Weight: Put on all your riding gear (helmet, shoes, pack, water) and weigh yourself. Enter this value in kilograms (kg) into the “Fully-Geared Rider Weight” field. This is the most critical step for accuracy.
- Select Your Bike: Choose your bike model from the dropdown list. Our Trek suspension calculator has different base settings for each model.
- Choose Your SAG: Enter your desired SAG percentage. For a plush, comfortable ride, choose something around 30-33%. For a firm, responsive, and efficient ride, aim for 25-28%.
- Read the Results: The calculator will instantly display your recommended starting Air Pressure in PSI and a suggested Rebound setting in “clicks from closed”.
- Apply and Test: Use a shock pump to set the pressure. Then, perform a SAG test to confirm. Set your rebound by turning the dial fully clockwise (closed), then backing it out by the recommended number of clicks. Go for a ride and fine-tune!
Key Factors That Affect Trek Suspension Results
Several factors beyond the calculator’s inputs can influence your final setup.
- Riding Style: Aggressive riders often prefer slightly higher pressure and slower rebound than what the Trek suspension calculator might suggest.
- Terrain: Smooth, flowing trails might allow for lower pressures, while steep, chunky terrain often requires more support to prevent bottom-outs.
- Air Temperature: Air pressure can change with ambient temperature. It’s good practice to check your pressure before every ride. You can learn more about this in our advanced suspension tuning article.
- Volume Spacers: Adding or removing volume spacers inside your shock changes the progressivity of the air spring. More spacers create more end-stroke support, allowing for lower initial pressure. Our Trek suspension calculator assumes stock volume spacers.
- Shock Service: A freshly serviced shock with new seals will have less friction (“stiction”) and may require slightly different settings than a shock that’s due for maintenance.
- Tire Pressure and Inserts: Your tire setup is part of your bike’s overall suspension system. Running lower tire pressures might mean you can add a little more pressure to your shock for support. Choosing the right bike is also crucial, check out our guide on choosing your Trek bike.
Frequently Asked Questions (FAQ)
Your suspension needs to support everything on the bike, including you and all your gear. Forgetting to include the weight of a 5kg hydration pack can lead to incorrect SAG and poor performance. The Trek suspension calculator is only as accurate as the weight you provide.
The calculator provides a starting point. Always perform a real-world SAG check. If your measured SAG is too high, add more air. If it’s too low, release some air. Trust the measurement over the initial number if there’s a discrepancy.
This is the standard way to measure rebound. Turn your red rebound knob all the way clockwise until it stops (this is “closed” or the slowest setting). Then, turn it counter-clockwise and count the clicks. A setting of “4 clicks from closed” is a common starting point.
No. This is a Trek suspension calculator and is specifically tuned for the leverage rates of Trek bikes. Using it for another brand will likely yield inaccurate results. You can read about different bike types in our Enduro vs. Trail comparison.
It’s good practice to check your shock pressure before every ride, as small amounts of air can leak over time. You should re-evaluate your entire setup with the Trek suspension calculator if your body weight changes significantly or you add/remove volume spacers.
Compression damping (usually a blue dial or lever) controls how the shock absorbs an impact. Unlike the settings in this calculator, compression is typically adjusted on-the-fly for climbs (more compression) or descents (less/open compression).
No. Coil shocks do not use air pressure. Setup for a coil shock involves choosing the correct spring rate (e.g., 450 lb/in) based on your weight and the bike’s leverage. This Trek suspension calculator is for air shocks only.
This could be due to a few factors. Your pressure might be too high (increase SAG), or your rebound might be too slow (“packing down”). Try reducing your air pressure by 5 PSI or speeding up your rebound by 1-2 clicks.