I've been doing some research into spring rates and length, trying to get a spring that matches the weight of my jimny.
Here's what I've found out so far.
Were not able to obtain any kind of information on ORA and Jimnybits springs. But it is possible to get a rough estimate of spring rate by measuring number of active coils, wire diameter and a few other parameters, enter the number in a spring rate calculator and voila.. there's the spring rate. From what I've learnt so far, these calculators aren't that far off.
Here's a calculator:
www.pontiacracing.net/js_coil_spring_rate.htm
Here's a link to the complete Old Man Emu catalogue:
www.arbusa.com/Uploads/PDF/onlineManuals...ME_Guide_current.pdf
Some info on King springs, which can be bought here:
www.euro4x4parts.com/parts/urh1038-1952_...ng_king_springs.html
These King H/D front springs are for a 2" lift. The rate for this spring is 140 lbs/inch. I don't have any other info on these springs. For more info, write an email to King springs, they answer witin a day or two.
Have some more info on Trail Master springs:
Spring no.
76043 jimny front 50mm lift
Wire diameter: 12 mm
Free Length: 368 mm
Spring rate: 26 N/mm ~ 148 lbs/inch
Spring no.
76053
Wire diameter: 13 mm
Free Length: 353 mm
Spring rate: 36 N/mm ~ 205 lbs/inch
Spring no.
76086
Wire diameter: 13 mm
Free Length: 368 mm
Spring rate: 40 N/mm ~ 228 lbs/inch
These are all front springs, as this is where the weight is mostly affected by winch, bumper and so on. But the OME catalogue also contains specs in rear springs.
As you can see, Trail Master and OME have different ways of how they make a lift. Looking a the 40mm lift diesel springs from OME, they're 360mm free length, where Trail Master +75mm Diesel springs are only 8 mm longer, but much harder.
I have only tried a rough measure of my ORA +4" springs and entered the numbers in the calculator. Ended with something around 130 lbs/inch. So really not at all suitable for a heavy bumper and winch, which I also suspected as I have a major sag with winch and bumper fitted.
EDIT
I've just tried entering the specs for a standard Jimny front spring.
Wire diameter: 11.2 mm roughly
Free length: 330 mm
no of active coils: 7 roughly
Spring rate 125 lbs/inch. OME catalogue states that standard Jimny springs are 120 lbs/inch, so the calculator is not that far off.
Just measured the Front off-side springs of my ORA springs.
Wire diameter: 12.1 mm, hard to tell exactly due to rust and paint falling off.
Free length: 430mm
No of active coils: 10
Spring rate: 105-110 lbs/inch
As you can see the ORA springs are essentially just very long, very soft springs. Softer than standard Jimny springs. Not even really suitable for a heavy bumper and winch if you ask me. I did suspect the ORA springs were soft, but not this soft.
