Techstop - Issue 20 - New Replacement Coil Springs

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NEW REPLACEMENT Issue 20/2018

COIL SPRINGS SHOCK ABSORBER, SUSPENSION, BRAKES, TOWBARS AND WHEEL ALIGNMENT SPECIALISTS

New Replacement Coil Springs

Mean diameter of spring

One of the most frequently asked question is “How do new replacement coil springs restore a vehicle’s standard ride height when they are lower in free height than Original Equipment units?”

When the mean diameter increases, the spring rate decreases. Active coils

Determining the number of active (working) coils varies The free height of a coil is important, however the way a according to spring design. Coils stop working when coil reacts at its “loaded ride height” is more significant. they are in contact with the spring mount or the coil All Pedders coil springs are designed with a heavier rate below them. As the number of active coils increases, the than Original Equipment. The rate for every coil for each spring rate decreases. uestions (F.A.Q.) asked is “Why are the new springs car is designed very carefully andreplacement is calculatedcoil using a hey are supposed to raise the car formula. to a restored ridecompress height. “load vs deflection” The standard coil will not Coil Spring Design as much at its loaded ride height therefore the starting There are two basic coil spring designs and they are: d rate coil height is somewhat but will not be as important of the important, “free length” shorter. as the “loaded gs are designed with a heavier rate. The rate for every coil for every car is• Linear rate Factors that determine springInrate ulated using a “load verses deflection” formula. doing so, as the rate is • Progressive or Variable rate much, so the starting height of the “free Length” will be shorter. There are three main elements to be taken into account Linear rate springs when designing a coil spring: g rate Linear rate springs maintain one spring rate throughout • Material size (wire diameter) most of their range of travel. For instance, if we have e taken into• account when designing a coil The mean diameter of the coilspring: a 350lb/inch linear rate spring that is 16 inches long, it will take approximately 350lb to deflect it 1 inch. It will • The amount of active (working) coils er) take another 350lb of load to compress it another inch, etc. until all coils bind, and the spring goes solid. This ls would represent 1050lb of load on a 16-inch spring that has now been compressed to 13-inch of loaded spring height. oil

placement Coil Springs

d they are:

spring rate per inch of deflection throughout most Figure 1. Springrate Rate spring that is 16 e have a 350lb/inch linear Spring rate refers to the amount of weight needed to weight to compress spring a given distance (Example:500lb 0lb toneeded deflect 1a inch. The next inch per of per compress a it spring a given distance (example:500lb inch). a spring for rate you need to know the factors that determine the rate ofan and the next inch of deflection will take To understand properly spring rate nly three things that affect and spring rate, socheck there'sanot that for much toyou need to know the factors that determine the rate of the e spring goes solid). At this point there will be spring. Fortunately, there are only three things that affect spring rate,than so there’s not thatwire. muchSo, to when remember. meter wire is stronger lesser diameter wire diameter is at has now been compressed to 13” of loaded Wire diameter

greater of wire the more strength in the de diameterThe of the springdiameter less one wire diameter. When the mean diameter finished coil and the spring rate increases. .

tive coils varies according to spring design. Count the total coils minus “locating” coils not “working coils. As the number of active coils .

Figure 2. Linear Rate Spring

s called “Variable Rate” springs. The purpose Straight advice, specialists you understand and... mpliance in the suspension over rough


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