Leverage Calculator For Shocks

Dial in rear suspension with a premium leverage ratio calculator built for mountain bike shocks. Enter wheel travel, shock stroke, sag target, and leverage curve assumptions to estimate average leverage ratio, sag at the wheel and shock, and progression across the travel range.

Shock Leverage Calculator

Use metric or imperial units. The calculator converts everything internally, then visualizes the leverage curve with Chart.js.

Average Leverage Ratio

2.50 : 1

Progression

17.9%

Shock Sag

18.0 mm

Wheel Sag

45.0 mm

Expert Guide to Using a Leverage Calculator for Shocks

A leverage calculator for shocks is one of the most useful tools for understanding how a suspension bike behaves under load. In simple terms, the calculator tells you how much rear wheel travel is created by a given amount of shock stroke. That ratio, often called the leverage ratio, is central to suspension tuning because it determines how the shock “feels” at the wheel. A higher leverage ratio means the wheel has more mechanical advantage over the shock, which usually creates a softer initial feel for a given spring rate. A lower leverage ratio means the shock has more control over the wheel, often improving support and bottom-out resistance.

For mountain bikes, shock leverage is rarely constant across the entire travel. Most modern linkage designs start with a higher leverage ratio and decrease through the travel. This is called a progressive leverage curve. Some bikes are more linear, while others are strongly progressive. The exact curve influences air spring tuning, volume spacer use, coil shock compatibility, sag setup, and how planted or poppy the bike feels on trail.

What the Calculator Measures

This calculator focuses on the most practical values a rider or mechanic needs:

• Average leverage ratio: rear wheel travel divided by shock stroke.
• Shock sag: how much the shock compresses at your target sag percentage.
• Wheel sag: how much the rear wheel settles into travel at the same target sag point.
• Progression percentage: the drop from starting leverage ratio to ending leverage ratio.
• Leverage curve chart: a visual estimate of how the ratio changes across travel.

These numbers help you compare bike platforms, evaluate whether a shock tune is appropriate, and estimate how changes in spring setup might affect ride feel. While this tool is not a substitute for manufacturer-specific linkage data, it is an excellent first-pass method for bike setup and shock selection.

Why Leverage Ratio Matters for Rear Shock Performance

The rear shock does not act directly at the axle. Instead, the wheel moves through a linkage that compresses the shock. That linkage creates mechanical advantage. If a bike has 150 mm of rear travel and a 60 mm stroke shock, the average leverage ratio is 150 / 60 = 2.50:1. That means every 1 mm of shock compression corresponds to about 2.5 mm of rear wheel movement on average.

This ratio matters because the same spring rate can feel very different on two bikes with different leverage. For example, a 400 lb/in coil on a bike with a 2.9 average leverage ratio will feel notably softer at the wheel than on a bike with a 2.4 average leverage ratio. Likewise, an air shock on a highly progressive frame may need fewer volume spacers than the same shock on a more linear frame.

Quick rule: higher average leverage usually means more wheel sensitivity for a given shock spring force, while lower leverage usually means more support and less wheel displacement per unit of shock stroke.

Typical Sag Targets by Riding Category

Sag is the amount of travel your suspension uses under your normal body weight and riding gear. It is usually expressed as a percentage of shock stroke or rear wheel travel. Choosing the correct sag is essential because it establishes ride height, traction, and the amount of remaining travel available for impacts.

Bike Category	Common Rear Travel	Typical Rear Shock Sag	Why Riders Choose It
Cross-country	100 to 120 mm	20% to 25%	Improves pedaling support, limits bob, and keeps geometry higher in the travel.
Trail	120 to 140 mm	25% to 30%	Balances efficiency, comfort, and grip on mixed terrain.
All-mountain / Enduro	140 to 170 mm	27% to 30%	Supports aggressive descending while keeping enough mid-stroke support for jumps and corners.
Downhill	180 to 200 mm	30% to 35%	Prioritizes traction and impact absorption on steep, rough tracks.

These ranges align closely with common setup guidance used by leading suspension brands and frame manufacturers. They are not absolute rules, but they are a reliable starting point for most riders.

How to Calculate Shock Leverage Correctly

1. Measure total rear wheel travel in millimeters or inches.
2. Measure the actual shock stroke, not eye-to-eye length.
3. Divide wheel travel by shock stroke to find average leverage ratio.
4. Enter target sag as a percentage.
5. If you know the frame curve, enter the starting and ending leverage ratios to estimate progression.

For example, if your bike has 160 mm rear travel and a 62.5 mm shock stroke, the average leverage ratio is 2.56:1. If your sag target is 30%, the shock will compress 18.75 mm at sag, and the wheel will move approximately 48 mm. That is a practical number when checking o-ring position during setup.

Linear vs Progressive Leverage Curves

A linear leverage curve changes very little from the beginning to the end of travel. Bikes with linear curves can feel predictable and easy to tune, but they may depend more on the shock’s internal spring curve or damping tune to create bottom-out support. A progressive leverage curve starts higher and ends lower, which means it gets mechanically harder to compress as travel increases. This often helps resist bottoming out and can improve compatibility with coil shocks if the frame is progressive enough.

Progression percentage is often calculated as:

((starting leverage ratio – ending leverage ratio) / starting leverage ratio) x 100

If a frame starts at 2.80 and ends at 2.30, progression is about 17.9%. That is a meaningful amount of progression and usually works well with many modern air shocks. By contrast, a frame that starts at 2.60 and ends at 2.45 is only about 5.8% progressive, which is relatively linear and may need more careful air spring tuning or stronger bottom-out support.

Example Frame	Start Ratio	End Ratio	Progression	General Tuning Implication
Linear platform example	2.60	2.45	5.8%	May rely more on shock tune, damping, or tokens for end-stroke control.
Moderately progressive example	2.75	2.35	14.5%	Often versatile with both air and some coil applications depending on bike intent.
Strongly progressive example	3.00	2.30	23.3%	Usually offers good bottom-out resistance and can favor aggressive descending setups.

What Is a Good Leverage Ratio for a Shock?

There is no single perfect number. In practice, many full-suspension bikes fall somewhere around 2.2:1 to 3.0:1 average leverage ratio, depending on travel category, packaging constraints, and intended ride feel. Lower average leverage ratios are often seen on designs that want more shock control and lower shaft speeds. Higher ratios may appear on layouts using shorter stroke shocks or prioritizing specific packaging and kinematic goals.

The important point is not just the average leverage, but the combination of average leverage, progression, anti-squat, damping tune, and spring curve. A bike with a 2.75 average leverage ratio can feel excellent if the progression and damper are matched well. Another bike with a 2.45 average ratio can still feel too soft or too harsh if the setup is wrong.

How the Calculator Helps With Air Shock Setup

Air shocks have inherently progressive spring curves because the air volume gets smaller as the shock compresses. If your frame is already highly progressive, an air shock may become very resistant late in the travel. In that situation, you may use fewer volume spacers, lower compression damping, or slightly more sag to maintain traction and full-travel usability. On a more linear frame, riders often add tokens or volume spacers to increase end-stroke support.

By calculating leverage and progression, you can estimate whether your bike is more likely to need a linear spring feel or additional ramp-up. This is especially useful before buying a new shock.

How the Calculator Helps With Coil Shock Compatibility

Coil shocks are much more linear than air shocks. Because of that, frame progression matters even more. Bikes with low progression can sometimes bottom out too easily on coil unless they use hydraulic bottom-out features or specific damping tunes. Bikes with moderate to high progression often work very well with coil because the frame itself provides enough end-stroke support.

If your leverage calculator shows a low progression number, that does not automatically mean a coil shock is a bad idea, but it does mean you should verify the frame manufacturer’s guidance first. Many brands publish explicit coil compatibility recommendations for this reason.

Common Mistakes Riders Make

• Using eye-to-eye shock length instead of stroke length.
• Assuming sag percentage at the wheel and sag percentage at the shock are different. They correspond through the leverage ratio.
• Ignoring progression and looking only at average leverage ratio.
• Choosing spring rates based only on rider weight without considering frame kinematics.
• Comparing bikes only by travel number without checking the leverage curve and shock size.

Real-World Setup Workflow

If you want to use this tool effectively, start with your frame’s published travel and actual shock stroke. Enter a sag target appropriate for your riding style. If your manufacturer provides leverage ratio charts, enter the topout and bottom-out values. Then compare the results to how the bike rides in practice:

1. Set baseline sag with riding kit on.
2. Check whether the bike rides too deep, too high, or uses travel too easily.
3. Review the calculated average leverage ratio and progression.
4. Adjust air pressure, coil rate, tokens, or damping accordingly.
5. Re-test on familiar terrain.

This approach helps connect on-bike feel with objective numbers. Over time, it also makes it easier to compare new frames or shock upgrades before spending money.

Useful Technical References

For readers who want to understand the engineering behind force, units, and mechanical relationships, these authoritative resources are helpful:

• NIST: Metric and SI unit guidance
• NASA: Fundamentals of force
• Penn State: Lever systems and mechanical advantage

Final Thoughts

A leverage calculator for shocks is valuable because it translates abstract suspension geometry into useful setup numbers. Once you know your average leverage ratio, sag displacement, and progression, you can make smarter decisions about shock pressure, spring rate, tokens, damping, and even whether a frame suits your riding style. Riders often chase settings by feel alone, but combining feel with leverage data leads to faster, more repeatable tuning.

Use this calculator as your first diagnostic step. Then confirm the results on trail, compare them against your frame manufacturer’s recommendations, and refine from there. Good suspension is never just about one number, but leverage ratio is one of the most important numbers to understand.

Data ranges above reflect commonly published industry setup norms for MTB suspension categories and standard engineering definitions of leverage and force relationships. Always verify frame-specific limits, shock stroke compatibility, and manufacturer coil recommendations before changing hardware.