Garage Files: How to Calculate Leverage Ratios
How to Calculate Leverage Ratios
Suspension has undoubtedly become more complex over the years with more purpose-built machines and various linkage designs, but the fundamentals have largely stayed the same. While there are many buzzwords and phrases when it comes to your suspension that can be difficult to understand, the concept of the leverage ratio is one of the most basic things you can understand to get the most from your shock. In this “Garage Files” we break down what a leverage ratio is and how it can affect your suspension. We will even show you the proper way to size your shock, so you can understand what type of shock you may need if you ever need to replace it.
There is a fairly simple equation to find the leverage ratio of your bike.
Finding the stroke can be a bit more complicated as some shocks aren’t designed to use the full body length in travel. In this case measure the body length, then let all of the air out of the valve. Compress the shock until the travel stops. Measure the exposed part of the body and subtract that amount from total body length. This method for measuring stroke will get you close, although it’s not always precisely accurate. If in doubt, most companies list the stroke measurement for the shock on their website under the “shock spec” info.
This 2018 Giant Anthem 29 had 90 millimeters of rear travel with a shock stroke of 42.5 millimeters. Using the equation dividing the wheel travel by the stroke of the leverage ratio, it comes out to 2.1. For a modern full-suspension bike, this is low.
This Rocky Mountain Slayer had 165 millimeters of rear-wheel travel with a 65-millimeter shock stroke. The leverage ratio for the Slayer is 2.53 to 1, which is a very average leverage ratio.
WHY DOES THIS MATTER?
You might be asking yourself why these ratios matter so much and how they change the ride of your bike. The relationship between the rear wheel travel and stroke determines how hard the shock must work to support rider weight and handle suspension damping. Most modern full-suspension bikes come with leverage ratios somewhere between 2 to 1 and 3 to 1. For nearly all riders, anything in this range will work well. However, heavier riders should note that higher leverage ratio bikes require stiffer springs and/or higher air pressures to function properly. This need for more support can also limit your tuning options, especially on bikes with very high leverage rates.
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