Ohlins Shock Calculator

Your expert tool for calculating optimal motorcycle suspension settings.

Sag Metric	Target Value	Acceptable Range (Street)

Target sag values based on your total suspension travel.

What is an Ohlins Shock Calculator?

An Ohlins shock calculator is a specialized tool designed to determine the optimal rear shock absorber spring rate for a motorcycle based on specific inputs like vehicle and rider weight. Unlike generic calculators, a precise Ohlins shock calculator focuses on the physics of suspension dynamics to provide a scientifically-backed starting point for tuning. Proper suspension setup is arguably the most critical factor for performance and safety, affecting handling, stability, and rider confidence. This tool is essential for serious track day enthusiasts, racers, and street riders who want to extract the maximum performance from their Ohlins suspension or any other brand.

A common misconception is that a factory shock setting is suitable for all riders. In reality, stock springs are designed for an “average” rider weight, which often doesn’t match the end-user. Using an incorrect spring rate—either too soft or too stiff—can lead to a host of problems including poor tire wear, instability under braking, and a harsh or unresponsive ride. Our Ohlins shock calculator helps eliminate this guesswork.

Ohlins Shock Calculator Formula and Mathematical Explanation

The core of this Ohlins shock calculator lies in a fundamental physics formula that balances the forces acting on the rear suspension. The goal is to select a spring that can properly support the combined weight of the motorcycle and rider while allowing the suspension to operate in its effective range. The primary formula is:

Recommended Spring Rate (N/mm) = (Total Force at Shock) / (Desired Sag at Shock in mm)

Here’s a step-by-step breakdown:

1. Calculate Total Weight: This is the sum of the vehicle’s weight and the fully-geared rider’s weight.
2. Calculate Desired Rider Sag at the Wheel: This is a percentage of the total suspension travel. For example, 30% of 130mm travel is 39mm.
3. Determine Shock Stroke and Sag at Shock: The movement of the shock itself is less than the wheel’s movement due to the suspension linkage. We find this by dividing the wheel travel/sag by the leverage ratio.
4. Calculate Force at the Shock: The total weight creates a downward force (Weight * 9.81 m/s²). This force is transferred through the linkage to the shock. The force on the shock is approximately the total force divided by the leverage ratio.
5. Calculate Required Spring Rate: Finally, we divide the force at the shock by the desired sag at the shock to find the ideal spring stiffness in Newtons per millimeter (N/mm). This is the core function of our Ohlins shock calculator.

Variable	Meaning	Unit	Typical Range
Vehicle Weight	Dry or wet weight of the motorcycle	kg	150 – 300
Rider Weight	Rider’s weight with all safety gear	kg	50 – 120
Suspension Travel	Total vertical movement of the rear wheel	mm	110 – 150
Leverage Ratio	Ratio of wheel travel to shock travel	Ratio	1.8 – 3.0
Target Rider Sag	Percentage of travel the suspension sags with the rider	%	25% – 35%

Practical Examples (Real-World Use Cases)

Example 1: Lightweight Sportbike

A rider with an 80kg weight (in gear) owns a Yamaha R6 weighing 190kg. The rear travel is 120mm and they want a track-focused setup with 28% sag. They are unsure of the leverage ratio, so they use an estimate of 2.3.

Inputs: Vehicle Weight: 190kg, Rider Weight: 80kg, Suspension Travel: 120mm, Target Sag: 28%, Leverage Ratio: 2.3.

Outputs from the Ohlins shock calculator:

– Total Weight: 270 kg

– Rider Sag at Wheel: 33.6 mm

– Recommended Spring Rate: ~101 N/mm. The rider should look for a spring close to this value.

Example 2: Heavy Adventure Bike

A rider weighing 100kg has a BMW R1250GS weighing 250kg. The rear travel is 200mm, and they want a comfortable street setup with 33% sag. The leverage ratio is known to be around 2.8.

Inputs: Vehicle Weight: 250kg, Rider Weight: 100kg, Suspension Travel: 200mm, Target Sag: 33%, Leverage Ratio: 2.8.

Outputs from the Ohlins shock calculator:

– Total Weight: 350 kg

– Rider Sag at Wheel: 66 mm

– Recommended Spring Rate: ~144 N/mm. This much higher rate is needed to properly support the significant weight.

How to Use This Ohlins Shock Calculator

1. Enter Vehicle Weight: Find your motorcycle’s “wet weight” (with all fluids) from the owner’s manual.
2. Enter Rider Weight: Weigh yourself while wearing all your riding gear (helmet, leathers, boots, etc.). This is crucial for accuracy.
3. Enter Current Spring Rate: If you know it, enter it. This helps the comparison chart. If not, the calculator still works.
4. Enter Suspension Travel: This is a critical value found in your bike’s specifications. Do not guess.
5. Enter Leverage Ratio: This can be hard to find. Searching online forums for your specific bike model might yield results. If not, a value between 2.2 and 2.5 is a reasonable starting point for most sport and street bikes. Using a correct value is important for the accuracy of this Ohlins shock calculator.
6. Set Target Sag: Choose your desired sag percentage based on your primary riding style.
7. Review the Results: The calculator instantly provides the recommended spring rate. Compare this to your stock spring to decide if a change is needed.

Key Factors That Affect Ohlins Shock Calculator Results

• Total Weight: This is the single most important factor. Even a small change in rider or luggage weight significantly impacts the required spring rate.
• Leverage Ratio: This acts as a force multiplier. A bike with a high leverage ratio needs a much stiffer spring than one with a low ratio, even for the same weight. You can learn more about this in our advanced suspension tuning guide.
• Riding Style: Aggressive track riders often prefer a stiffer setup (less sag), which provides more feedback and support during high-G-force maneuvers. Street riders usually prefer a plusher ride (more sag).
• Suspension Travel: Bikes with more travel can run a higher sag percentage while still having enough travel to absorb bumps.
• Spring Preload: Preload doesn’t change a spring’s stiffness, but it adjusts the ride height. Our Ohlins shock calculator finds the correct stiffness; you then use preload to set the sag correctly. A guide on how to set shock preload can be very helpful.
• Damping Settings: While the spring supports the weight, the damping (compression and rebound) controls the speed of the suspension movement. Once you have the right spring, you must adjust your damping. This is a topic our Ohlins shock calculator does not cover, but is essential for a complete setup.

Frequently Asked Questions (FAQ)

1. What is “sag” and why is it important?

Sag is the amount your suspension compresses under weight. Static sag is the compression under the bike’s own weight, while rider sag is the compression with you on board. Correct sag ensures the wheel can extend into dips as well as compress over bumps, keeping your tire in contact with the road. It’s the first step in any motorcycle suspension setup.

2. Can I use this ohlins shock calculator for any brand, not just Ohlins?

Yes, absolutely. The physics of spring rates and forces are universal. This calculator is named an Ohlins shock calculator for its precision and target audience but the results (in N/mm or lbs/in) are applicable to springs from any manufacturer (like K-Tech, Showa, WP, etc.).

3. What if the recommended spring rate is between two available sizes?

This is a common scenario. As a general rule, it’s better to round up to the next stiffer spring. A slightly too-stiff spring can be managed with damping and preload adjustments, whereas a too-soft spring may bottom out, which is dangerous. Our Ohlins spring rate guide has more details.

4. My bike’s handling feels terrible. Will a new spring fix it?

It’s the most likely solution if the spring rate is incorrect for your weight. An incorrect spring rate is the root of many motorcycle handling problems. After installing the correct spring and setting sag, you may still need to adjust damping, but the spring is the foundation.

5. How do I measure my current sag?

You need a friend to help. First, measure the rear suspension fully extended (wheel off the ground). Then, measure it with the bike under its own weight (static sag). Finally, measure it with you on board in your normal riding position (rider sag). The difference between these measurements is your sag. The process is detailed in our guide on how to measure rider sag.

6. Does this ohlins shock calculator work for front forks?

No, this calculator is specifically for the rear mono-shock. Front forks have different mechanics (two springs, different angles) and require a separate calculation. We have a dedicated calculator for that.

7. What is N/mm?

N/mm stands for “Newtons per millimeter.” It’s a unit of force that defines the stiffness of a spring. For example, a 100 N/mm spring requires 100 Newtons of force to compress it by 1 millimeter. This is the standard unit used by Ohlins and other high-performance brands.

8. Is this calculator suitable for track day preparation?

Yes, it’s an ideal tool for track day bike preparation. For the track, you would typically select a lower sag percentage (e.g., 25-28%) in the Ohlins shock calculator to get a recommendation for a stiffer, more responsive setup suitable for high speeds and smooth surfaces.