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KW V3 spring rates?

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  • #31
    Originally posted by inside View Post
    what are the downsides of running without helper springs? Noisy transition on jumps when spring gets fully released?
    The helper springs are there to ensure that the main spring is properly located on the spring perches at ALL times, when there is no load on the dampers, otherwise the main springs would get displaced when the dampers opened sufficiently to stop them remaining captive. This would produce punctures and serious handling problems.

    The only other alternative to using a helper spring would be to use longer main springs, but with spring rates much higher than that used in helper springs, the dampers would be working most of the time near to the full extension of the damper pistons, rather than in mid-range with helper springs. The use of helper springs effectively gives a 2-stage spring, where the helper spring is intended to become a coil-bound spring-length "reducer" under driving loads
    /// Exdos ///
    "Men who try the impossible and fail spectacularly are infinitely superior to those who reach for nothing and succeed" --Napoleon Bonapart

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    • #32
      I would add that the helpers also help to push the dampers towards full extention when the car become light, helping to keep the wheels on the ground.

      You can get a 4lb/inch x 2" long helper spring that compresses to a length of only 7.5mm, this obviously greatly helps in the raising of the lower spring perch, but will only keep the main spring located and not really help with keeping the wheels on the ground. For comparisson, the standard KW helper is approx. 85lbs/inch, 83mm free length & 30.5mm fully compressed.
      2000 Cosmos Black S50, Kyalami/Black interior, KW V3s, H&R ARBs, Supersprint exhausts, Apex ARC8s.
      1996 Dark Aubergine Escort Cosworth Lux with leather, GGR 305 chipped, GGR/Koni suspension, Black Diamond discs.
      2008 Orange/Black Westfield Megabusa, FW rear, Widetrack/Nitron Suspension, AP/Westfield 4 pots.
      Lots of Land Rovers!
      No wife or kids!!

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      • #33
        Originally posted by Limbs View Post
        I would add that the helpers also help to push the dampers towards full extention when the car become light, helping to keep the wheels on the ground.
        Doesn't gravity do that?
        /// Exdos ///
        "Men who try the impossible and fail spectacularly are infinitely superior to those who reach for nothing and succeed" --Napoleon Bonapart

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        • #34
          Originally posted by exdos View Post
          Doesn't gravity do that?
          If the car's airborn, the wheels will want to be too!
          2000 Cosmos Black S50, Kyalami/Black interior, KW V3s, H&R ARBs, Supersprint exhausts, Apex ARC8s.
          1996 Dark Aubergine Escort Cosworth Lux with leather, GGR 305 chipped, GGR/Koni suspension, Black Diamond discs.
          2008 Orange/Black Westfield Megabusa, FW rear, Widetrack/Nitron Suspension, AP/Westfield 4 pots.
          Lots of Land Rovers!
          No wife or kids!!

          Comment


          • #35
            Originally posted by Limbs View Post
            If the car's airborn, the wheels will want to be too!
            Newton's Third law. As the car gets airborne at one end of the spring on the damper, the wheels get pushed in the opposite direction by the release of energy stored in the spring at the other end of the damper and then gravity takes over...

            Last edited by exdos; 11-12-2011, 08:47 PM.
            /// Exdos ///
            "Men who try the impossible and fail spectacularly are infinitely superior to those who reach for nothing and succeed" --Napoleon Bonapart

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            • #36
              Originally posted by exdos View Post
              the wheels get pushed in the opposite direction by the release of energy stored in the spring
              Exactly, so if the helper spring is only 4lbs it's not going to be doing much pushing!!
              2000 Cosmos Black S50, Kyalami/Black interior, KW V3s, H&R ARBs, Supersprint exhausts, Apex ARC8s.
              1996 Dark Aubergine Escort Cosworth Lux with leather, GGR 305 chipped, GGR/Koni suspension, Black Diamond discs.
              2008 Orange/Black Westfield Megabusa, FW rear, Widetrack/Nitron Suspension, AP/Westfield 4 pots.
              Lots of Land Rovers!
              No wife or kids!!

              Comment


              • #37
                I thought the whole reason for having the helper springs was due the the ride height adjustment. The helper spring is there to take up the variable space between the top of the main spring and top mount caused by different ride height settings.

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                • #38
                  I always assume it's to help locate the spring in full extension, nothing to do with the ride height (well apart from it's compressed length). Certainly nothing to do with the helping the wheels keep on the ground I would say! - it's poundage is nothing compared to the main spring; it's the body that's jumping the wheels might leave the ground if there's not enough droop travel or the rebound is stiff.
                  Last edited by c_w; 12-12-2011, 09:55 AM.

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                  • #39
                    Originally posted by c_w View Post
                    I always assume it's to help locate the spring in full extension, nothing to do with the ride height (well apart from it's compressed length). Certainly nothing to do with the helping the wheels keep on the ground I would say! - it's poundage is nothing compared to the main spring; it's the body that's jumping the wheels might leave the ground if there's not enough droop travel or the rebound is stiff.
                    Yes, so basically the helper spring is a varable spacer. If you run high then it has less space to make up when the strut is on full extension.if you run low then it has more space to make up so the main spring stays located.

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                    • #40
                      Originally posted by c_w View Post
                      I always assume it's to help locate the spring in full extension, nothing to do with the ride height (well apart from it's compressed length). Certainly nothing to do with the helping the wheels keep on the ground I would say! - it's poundage is nothing compared to the main spring; it's the body that's jumping the wheels might leave the ground if there's not enough droop travel or the rebound is stiff.
                      AT LAST! We're 100% in agreement on something!
                      /// Exdos ///
                      "Men who try the impossible and fail spectacularly are infinitely superior to those who reach for nothing and succeed" --Napoleon Bonapart

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                      • #41
                        Originally posted by exdos View Post
                        AT LAST! We're 100% in agreement on something!
                        I see it as you having come round to my correct way of thinking

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                        • #42
                          Originally posted by c_w View Post
                          I see it as you having come round to my correct way of thinking

                          True to form: you would!
                          /// Exdos ///
                          "Men who try the impossible and fail spectacularly are infinitely superior to those who reach for nothing and succeed" --Napoleon Bonapart

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                          • #43
                            Originally posted by exdos View Post
                            True to form: you would!
                            -

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                            • #44
                              Originally posted by exdos View Post
                              AT LAST! We're 100% in agreement on something!
                              I'm not!!

                              Originally posted by exdos View Post
                              The use of helper springs effectively gives a 2-stage spring
                              Originally posted by c_w View Post
                              it's poundage is nothing compared to the main spring; it's the body that's jumping the wheels might leave the ground if there's not enough droop travel or the rebound is stiff.
                              Exactly, the main function of the suspension is to keep the wheels on the ground as much as possible, in an ideal world, the car would have infinite suspension travel and would always keep the wheels on the ground. In reality that is not possible, but having the two-stage main/helper arrangement allows you to have a stiff main spring which facilitates a low ride height. The secondary (helper) spring keeps the main spring seated and ensures that the suspension can travel to full extension, overcoming the dampers rebound which is set to stop the car bouncing in reaction to the main spring’s action.

                              For the purpose of trying to achieve the fitment of a 9.5” wheel, using a 4lb helper spring is by far the best option, but I do not believe that it is the best option for the car’s handling. If the helper spring’s only job was to keep the main spring seated, why are there various different rates available? The lightest spring would always be used as it is weighs less, compresses more & is cheaper to make and buy!!

                              Do not forget that, at the time that the car goes airborn, the physics of the situation are that, if it were not for the springs, gravity would bring the wheels back down to earth at exactly the same time as the rest of the car!!
                              2000 Cosmos Black S50, Kyalami/Black interior, KW V3s, H&R ARBs, Supersprint exhausts, Apex ARC8s.
                              1996 Dark Aubergine Escort Cosworth Lux with leather, GGR 305 chipped, GGR/Koni suspension, Black Diamond discs.
                              2008 Orange/Black Westfield Megabusa, FW rear, Widetrack/Nitron Suspension, AP/Westfield 4 pots.
                              Lots of Land Rovers!
                              No wife or kids!!

                              Comment


                              • #45
                                Originally posted by Limbs View Post
                                Do not forget that, at the time that the car goes airborn, the physics of the situation are that, if it were not for the springs, gravity would bring the wheels back down to earth at exactly the same time as the rest of the car!!
                                When the car goes airborne (UPWARDS) there is an "equal and opposite reaction" (Newton's Third law) at both ends of the spring, so the wheels are simultaneously forced DOWNWARDS by the energy previously stored in the springs when they were compressed. In view of the fact that each front wheel/ suspension/brakes (unsprung weight) weighs considerably less than the body of the car (sprung weight), the wheels will be forced downwards by the recoil of the spring with greater acceleration than the body of the car is forced upwards. An analogy of the situation is like a spring-loaded air rifle releasing it's energy, where at one end of the spring, the pellet weighing a few grammes is shot forwards faster than the speed of sound whereas at the other end of the spring (where there is an equal and opposite reaction) the weight of the rifle and the person holding it, weighing considerably more than the pellet, hardly suffers any backward movement under recoil of the spring.

                                Since the poundage of the main spring on a KW Front damper is many times greater than the poundage of the helper spring, all the spring force acting downwards on the wheel when the car goes "light" must come from the main spring and the helper spring, of lesser force, can add nothing, then gravity will take over because the wheels are already moving DOWNWARDS and the wheels will then hang from the car at the full extension of the damper, as shown in the photo of the Fiat.

                                As previously stated, the helper spring is only there to ensure the spring doesn't get displaced when the dampers get extended beyond the length of the main spring. See what KW has to say on the subject: http://www.kw-suspension.com/us/kw_faqs.php
                                My helper spring is fully compressed, is this normal?
                                Yes, that is how it is designed. When your suspension is fully extended, the main spring is free to move around and can come dislodged from its perches without a helper spring. The helper spring is only there to retain pressure on the main spring when the shock is fully extended so that the main spring stays in place.
                                /// Exdos ///
                                "Men who try the impossible and fail spectacularly are infinitely superior to those who reach for nothing and succeed" --Napoleon Bonapart

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