Motorcycle rear shock spring rate calculator

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motorcycle rear shock spring rate calculator

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Basic Spring Calculator

How do i select a spring rate? To make selecting a spring rate easier, we took a different approach. When you arrive at the product page and are ready to add a fork cartridge, valve kit or shock to your cart, you will have to select a spring rate.

There will be a dropdown list of rates for you to choose from. In most cases there will be five rates to choose from. The site will select, by default, the rate most appropriate for a pound rider. Without Gear The next softer rate covers pounds and the softest under The two stiffer rates are recommended for and over respectively. If you select this one, we will contact when we process the order to discuss your needs.

Spring rates are a tuning variable and should be changed for different track, road and load conditions. We realize that this is impractical for street riders as changing springs when you pick a passenger and then changing back when you drop them off is far too much work.

Racers on the other hand, will change spring rates with changing track and weather conditions. In fact a firmer rate with less pre load gives a plusher ride than a softer rate with more preload. Spring rates and preload will determine the range of stroke that the bike uses.This is to give you a guideline of what spring rate you need, there are other variables that may require you to need a softer or firmer spring rate.

Click here to go to our Advanced Spring Calculator. If you're purchasing from us, please get in touch and we'll look at the finer details for you with the use of some software that simulates your bike kinematics and your riding position. How do I determine the stroke of my shock? Find out from Manufacturer — look in your user manual for your bike or go to the manufacturers website and find specifications for your bike. You will be given a size for the shock which will look something like this — 8.

The second part, or the smaller value, relates to the stroke length. They may give the dimensions in millimetres, to convert divide by Measure you shock — to measure your shock take the distance from the main body of the shock to the end of the shaft, see pic below If you are unsure please contact us.

The spring rate is the amount of force required to compress the spring over a set distance. Search Home Shop Expand menu Collapse menu. Service Expand menu Collapse menu. About Expand menu Collapse menu. Setup Expand menu Collapse menu.

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motorcycle rear shock spring rate calculator

Click for more info Rider Weight lbs :. Wheel Travel inches :. Shock Stroke inches :.Request call. My Account. Orders Comparison list Wish list Track my order s. Track my order s. Sign in Register Email. Password Forgot your password? Register for a new account. Sign in.

Remember me. View cart. Tech Product Ridetech Rides Action. The steps below will help you to find an approximate spring rate for your coil-over application. Enter your suspension measurements in the white boxes below.

This calculator will only give approximations depending on the accuracy of your information. Use at your own discretion. Vehicle Rear End soild axle :. Use an accurate racecar scale that will weigh each corner of your car.

A trucking company scale meant to weigh 80,lbs may not be accurate enough for a lb car. Make sure the vehicle is loaded with driver, passenger, and cargo just like you will drive it or race it.

motorcycle rear shock spring rate calculator

Example corner weight using weight balance: To get the corner weight of your car, take an example total weight of lbs and multiply it by the front end weight bias. Then divide that number by 2 to get the corner weight of the front end of the car. Front Unsprung corner weight is usually around lbs. Rear Unsprung corner weight is usually around lbs.

Sprung Weight:. It is the weight supported by the spring and is the only weight used in calculating spring rates. Step 2 - Calculating Motion Ratio The "motion ratio" is the mechanical advantage lever ratio that the wheel has over the spring in compressing it. Dimension A:. Dimension A - Measure the distance from the control arm pivot point on the subframe centerline of the bushing to the point on the control arm directly under the center of the spring or the "coil-over assembly.

Dimension B:. Dimension B - Measure the distance from the control arm pivot point on the subframe to the centerline of the ball joint. For simplicity, we are going to ignore motion ratio for the rear.

It should be close to 1. If you have a vehicle with an independent rear suspension end select the Vehicle Front End and independent rear option above. Step 3 - Coil Spring Angle Spring Angle: 90 89 88 87 86 85 84 83 82 81 80 79 78 77 76 75 74 73 72 71 70 69 68 67 66 Using a protractor or similar measuring device, measure the angle of the centerline of the spring or "coil-over assembly" from the horizontal of the control arm or axle if calculating the rear.

In most cases, this will be somewhere between 75 degrees and 90 degrees.Ultimately, the best spring rate is the one that best suits your personal preferences for your riding style.

Be careful! Although you may be well within limits for avoiding coil binding, using excessive preload will overly stress the shock, leading to possible premature failure. Or, simply ride with the calculated spring rate and let personal preferences make your determination. Enter your input parameters and click "Submit" to calculate your spring rate, or "Reset" to start over:. Total Riding Weight pounds : includes the rider and anything else added to the bike; e.

Rear Weight Bias percent : the standard formula is based on arear-to-front total weight distribution. A more accurate way would be to use a bathroom scale under the rear wheel and a 2x4 under the front wheel, to determine the true sprung weight at the rear wheel. Position your body according to your riding style, and then enter this value for your total weight. A zero-preload spring rate is determined, then preload is applied to calculate the corresponding sag.

Choose a sag appropriate to your riding style. If you are an extreme rider jumps, drops, big hits, etc. Preload Adjuster number of turns : a minimum of 1. The canned value is a best guess of the effect ECE will have on preload adjustment. It is a percentage of the overall spring rate used in calculating the spring tension for the specified turns of preload.

Input Parameters. Output Parameters. Optional Spring Rates. Preload Precautionary. Preload adjusters apply about 1 mm or. If the spring is not marked as to its real stroke, never use more than 2. If the spring is marked as in x 1. Correction For Suspension Progression. Correction For Stable Platform Shocks. If you have already corrected for suspension progression, try a 50 pound lighter spring, otherwise try a pound lighter spring. Reference Links.All springs are manufactured in Europe or the U.

NONE from Asia to meet our standards and specifications. Custom made springs or spring rates are available. One year guarantee against breakage. For example, if it takes 25kg of force to compress the spring one inch, it will take another 25kg 50kg in total to compress it the second inch and so on until the end of the travel. Progressive Rate — are wound progressively from a finer pitch at one end to a coarser pitch at the other, therefore having a rising rate resistance to compression.

For example, a 15kg to 25kg progressive spring rate will take 15kg of force to compress the spring one inch, then an additional 17kg of force the next inch and so on until the end of the travel, the last inch takes an additional 25kg to compress it. Straight rate vs progressive rate? Progressive spring rates for PDS shocks only allow additional tuning latitude for professional tuners.

For shocks with stock valving we prefer straight rate springs. All springs are the exact dimension as the O. No additional spacers required. We also offer custom made springs for non-standard applications. Almost every spring page on our site list the make, model and year that the springs fit AND there are spring charts on those pages.

Just plug-in your weight including gear and it will show the rate you need. Please be short and concise with your request. Long emails with many questions will NOT be answered. NOTE: Most guys estimate the weight of their gear and are usually wrong. Weigh your gear, you will be surprised.

Trail riding gear the above items plus water pack, tools, spares lbs. Exchange Program — Shock springs purchased from Slavens Racing may be installed, checked for correct sag measurements and exchanged for a different rate if the measurements are not correct.

Springs that have been ridden, damaged or scuffed will not be accepted for exchange or return. This program is only offered by Slavens Racing. Sign Up Now. Select Model. Your garage is empty. One year guarantee against breakage or rate change on ALL springs. To receive the Slavens Racing email newsletter please signup.

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Follow Us.Finally computer software to tune a shim stack. The general wisdom for dirt bike spring selection is:. Based on those guidelines virtually any spring could be used. Regardless of spring rate the suspension is required to produce Using a softer 0. Since race sag is set with the forks bleed there is no difference in air spring force.

The spring rates available from Racetech and Eibach are:. Shock Linkage Ratio Link suspensions systems have created a lot of confusion in the motorcycling community.

Multiple pivot points, complex angles, year-to-year changes coupled with all of the pre-production hype have led many riders to believe linked suspensions produce complex shock compression profiles.

The fact is link systems are nearly linear in the range where race sag is set. For comparing setups with the same race sag link ratios are exactly the same when the suspension is in the same stroke position. Link systems used in MX suspension setups produces a nearly linear motion at the top of the stroke. Linked suspension systems require two parameters to determine force at the rear wheel. Travel ratio [TR] defines the position of the shock shaft given the wheel position. Link ratio [LR] defines how much the shock shaft moves for an incremental change in wheel position.

The ReStackor physics section works through those parameters to determine the relationship between spring force at the shock and spring force at the wheel:. Using that equation the change in force between free sag and race sag the rider rear wheel weight is:.

Add in the assumption link ratios do not change much over the range where race sag is set and the above equation reduces to a simple ratio of race and free sag. Shock Spring Rate Selection The assumed baseline setup is a spring rate of 5.

Rear Shock Spring Rate Calculator

Changing the setup to use 1. Letting the free sag range float between 0. That spring rate range spans the entire range of springs available from Race Tech and Eibach:. Same thing goes for a fork. Those guidelines are just too broad to be of any use selecting spring rates. The fundamentals of spring-mass-damper theory provide the equations needed to quantify suspension response as a function of spring rate, damping and bump height.

Programming the equations below into a spreadsheet gives a tool that describes suspension travel as a function of spring rate, damping and size of the initial blow, bump height. The range of available fork spring rates 0. Plugging that spring rate range into the impulse response function gives the suspension bump response shown below.

As expected, a softer spring produces more suspension bump travel. Suspension response to an impulse blow can be directly computed as a function of spring rate and damping.

Softer springs produce more suspension travel. Bump travel can also be controlled by changing compression damping.

The suspension response equation shows the effect of compression damping changes on bump travel. By increasing compression damping the softer spring can be made to produce the same suspension bump travel as the baseline blue curve case. Compression damping can be re-tuned for control of suspension bump travel in a motorcycle suspension setup. A basic use of ReStackor is to figure out the shim stack modifications needed to generate some target damping curve.

The baseline case in the above example has a simple tapered stack configuration generating a damping coefficient of 0. ReStackor pro calculation of compression damping coefficient for the baseline motorcycle fork suspension setup.The item selected will only fit the motorcycles listed. Please select your bike here to see all the parts that fit your motorcycle.

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