Spring Height vs. Lift

I know the subject of suspension has been beaten to death but I haven’t found an answer to this question. Not on this forum or elsewhere.

I have seen numerous comments about springs that are rated for a certain lift but, in reality, don’t provide the lift that they claim. What I would like to understand is whether that is due to the manufacturers simply categorizing them or if it’s due to them being installed on vehicles that are already heavier than stock. After I installed my front and rear bumpers, along with a roof rack, my Jimny now sits 20+ mm lower. Not exactly a surprise. Neither would I be surprised if I purchased springs designed to lift a Jimny at curb weight by 40mm and they only lifted my heavier Jimny 30mm. I wouldn’t be concerned except I am not likely buying a lift kit but rather longer springs and shocks separately. When I do, I would like to make sensible decisions.

Any help and comments are appreciated.
Bob

As much as anything what you need to know from the manufacturer or suppliers is the actual spring rate being used. This is normally expressed in pounds per inch. Free length also comes into the equation. Basically there are two ways to get a lift, first being longer springs of the same rate as standard which give you a similar suspension feel but with more body roll and more height and articulation off road, second is a stronger spring of the same height this will make it taller but will also make the ride really harsh and will limit articulation on an otherwise standard car. However if the car is noticeably heavier than stock for whatever reason then this complicates the spring choice. With a heavy car a harder stock height spring if matched to the increase in vehicle weight will regain the standard height and feel of the suspension despite the extra weight, longer standard rate springs will regain the lost height but the suspension will feel soft and potentially be unstable making it impossible to corner without excessive body roll or even falling over. In this situation to gain a lift needs a stronger and longer spring. In order to get this really spot on you would need to corner weigh the car and then using the factory springs as a base work out how much more each corner weighs, how much it has dropped as a result of the extra weight and how high you wanted to be when done and then calculate the rate and length of each spring in order to balance the car evenly front to back and side to side. This is neither cheap nor particularly simple to do properly. The other thing is that making the car heavier and higher will affect the handling because of physics and whilst suitable adjustment can be done to mitigate the effects it is always going to be less stable than a factory spec car.

Unfortunately because the car is a jimny not a land rover my knowledge of availability of off the shelf springs to solve your problem is non existent, sorry. That said others may well know especially Tom DK.

Thanks for the reply. I have sent inquiries to several of the spring manufacturers for the same basic information you mention. I don't know if this is just a very busy season for suppliers of offroad accessories but I haven't heard back from anyone yet. Maybe I'm just too impatient.

My assumption has been that the Jimny specific springs designed for a 2 inch lift have been designed with a spring rate and height that would accommodate the base weight of the Jimny (or equivalent) providing the advertised lift.

Touching on one point you made, I am not a fan of a lot of lift. I may be a minority but I think it is practical to keep it as close to stock as possible, taking into account other mods. I am looking to recover what I have lost along with a little additional.

Thanks again.

A few months ago I was talking with pi springs at a show about this and whilst they don't currently have an off the shelf solution what they were offering was a custom set of progressive springs so soft for normal and hard for work,only downside being 1200 pounds in cash and them needing the car for 2 weeks. Very cool but not cheap.

zukebob wrote: I know the subject of suspension has been beaten to death but I haven’t found an answer to this question. Not on this forum or elsewhere.

I have seen numerous comments about springs that are rated for a certain lift but, in reality, don’t provide the lift that they claim. What I would like to understand is whether that is due to the manufacturers simply categorizing them or if it’s due to them being installed on vehicles that are already heavier than stock. After I installed my front and rear bumpers, along with a roof rack, my Jimny now sits 20+ mm lower. Not exactly a surprise. Neither would I be surprised if I purchased springs designed to lift a Jimny at curb weight by 40mm and they only lifted my heavier Jimny 30mm. I wouldn’t be concerned except I am not likely buying a lift kit but rather longer springs and shocks separately. When I do, I would like to make sensible decisions.

Any help and comments are appreciated.
Bob

In short. You need to buy springs that match the sprung weight of your vehicle. This is why I always recommend getting springs from either trail master or OME as all their springs are with known spring rates. Rather that than buying cheap springs of unknown origin and rates.

If your Jimny is that heavy perhaps you should take a look at the diesel springs from trail master

Thanks to both of you. I know that I’m not just being impatient, but lazy and cheap as well. As a retired engineer that worked for a company designing and producing military vehicles, I learned one important thing. I would trade a handful of the engineers in my group for one well experienced field service rep who had significant hands-on experience.

11/60: progressive rate springs, specifically dual rate, is one of the things I was pursuing. Tough Dog apparently makes dual rate. OME, King and Dobinsons all make progressive rate springs but none list any specifically for the Jimny. I’m guessing none of them have any, producing only the linear rate. Perhaps when I finally get a reply (if I do), I will finally know.

Tom: OME was my first plan but then I thought maybe a quality set of Jimny springs with either Bilstein or Amada Extreme shocks. Started to move away from OME hearing that they tended to be somewhat soft. King springs apparently have the same reputation. I think now it’s time to probably go back to OME and start my own hands-on experience.

Thanks to both for the feedback.