Spring Data

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Now that I've started looking at lifting my iO, I thought I would tabulate the spring data in one place so that the next person along doesn't have to wade through the forum looking for the details.  Consider it a "companion thread" to the "strut data" thread.

The information below is taken from various publically available documents - the source will be noted, along with any exceptions.


OEM springs - information from the FSM in the resource section.

Front springs - 3 door - wire diameter 14mm, free length 365mm, average diameter 160mm

Front springs - 5 door - wire diameter 14 mm, free length 376/386mm, average diameter 160 mm 

Rear springs - wire diameter 11mm, free length 306mm, average diameter 131mm

I have no verifiable information on spring rates - please note the FSM states average diameter which is presumably from center-to-center of the wire, so add one wire diameter to get outer diameter.


KYB OEM replacement springs - information from KYB's web site

Front springs - RA1958 - wire diameter 14mm, free length 372mm, outer diameter 172mm

Rear springs - RD6420 - wire diameter 11.5mm, free length 316mm, outer diameter 141mm

KYB does not state spring rate, presumably, since these are all OEM replacement, the spring rate will be similar to the OE springs - the details of the MAZDA spring commonly used to lift the rear of the iO are below.

RD1430 - wire diameter 12mm, free length 340mm, outer diameter 147mm


King Springs - information provided via email

Front springs + 20mm lift - older models longer spring - KMFS900 - free length 365mm, spring rate 165 lb/in

Front springs + 20mm lift - newer models shorter spring - KMFS900SP - free length 345mm, spring rate 165 lb/in

Rear springs +30~40 mm lift - KFFS90 - free length 290mm, spring rate 165 lb/in


Ironman- for 99 onwards

Front springs - MITS034B - 0-50kg +35mm lift - wire diameter 16mm, free length 367mm, 200 lb/in.

Rear springs - MITS035B - 0-200kg +35mm lift - wire diameter 14mm, free length 315/305mm, 229 lb/in

Information taken from the Ironman catalogue Vol. 15 - there are some suggestions that Ironman are no longer making these springs, they have not yet responded to my email queries.

A note with MITS034B states - Vehicles with independent suspension must maintain a minimum of 60mm downward suspension travel.


Dobinsons Spring & Suspension - for 99 onwards

Front springs - three door - C43-114 +28mm lift - 230 lb/in

Front springs - five door - C43-240 +30mm lift - 245 lb/in

Rear springs - C43-115 +35mm lift - 202 lb/in

Dobinsons does not make the details of their springs available to the public, they were provided to me but because it came with a note saying it was not available to the public I will not provide them here - I have chosen to provide the spring rates as that is perhaps the most critical one when making your choice.


Random comments & observations ...

My only experience with lift springs has been with OME on my SQ420 Grand Vitara, I have, quite frankly, been very happy with those, they run about 25% over the OE spring rate - if OME offered springs for the iO - I would have fitted those a long time ago - some of you may remember my quest to find OE springs when I first got the car, I would have happily gone with OME instead of those.

There are various threads with various spring rates mentioned - at least one person has attempted to calculate the spring rate on the OE springs coming up with 170 lb/in for the front springs, I've also seen some one else claim 150 lb/in for the OE front, and 175 lb/in for the King front.  I happen to have a pair of the OE front springs on a shelf, so I made my own measurements and did my own calculations - I did get a figure very close to that 170 lb/in one, on my first try, but, recognizing that very small errors in measurement can produce significant changes in the numbers, I "ran the numbers" several times and got significant variations - both higher & lower.

The OME guide for a JB420 Suzuki Grand Vitara, which uses a "coil over" spring/strut similar to these shows 160 lb/in for the OEM front so both the 150 & 170 numbers for the OE are believable, the 165/175 lb/in for the King spring sounds low (OME springs for the same model GV is 200 lb/in).

The King springs seem to the "go to" choice, once attention is paid to which strut you have and the correct spring is chosen - I came across a couple of dire warnings on not using Dobinsons front springs - these appear to relate to the 1.6 engined three door, at least one person with the five door seems to like his, I found one person using the Ironman springs on a three door - he's not 100% satisfied - he seems to like the ride  (says it's more comfortable on the road) but he seems to have a problem with droop - I can't help but wonder is this issue is specific to the three door models.

If any one has access to credible sources of information on the OEM spring rates - please share.


Today I did a very crude "spring rate" test on the OE front springs - I measured the free height (length) and then had my son stand on one spring - that 170 lb/in rating that was calculated (it was either Bob or Glen) looks like it's right on the money - it makes me wonder about the King springs stated 165 in/lb - based on FSM data & personal measurements, there would be no way for a King spring with a spring rate that close to the OEM rate and a shorter free length to lift the vehicle.

Using a "turn count" of 5.5 turns (JOHNICUE's pictures in Fab72's "broke my strut" thread) and a 16mm wire diameter (somewhere else in the forum), a calculation of the Kings KMFS900 spring rate comes up with 253 lb/in.

OsakaBane (OBK), a Japanese manufacturer of OE replacement springs has provided a figure of 2.8 (presumably kg/mm) as the spring rate for their C4M-67061 replacement front spring - this works out to approximarely 157 lb/in - I will try to get more details about the OBK springs.


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