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      07-12-2012, 07:20 AM   #1
Kgolf31
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OEM Spring Rate - Z4M Coupe

Has anyone ever figured this out?

I've been searching and searching to no avail. They aren't progressive springs, are they?
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      07-12-2012, 07:54 AM   #2
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Yes they are progressive.

Spring rates (lbs)

Stock Front (1-4 inches of travel after preload)
160-220

KW V3 Front (1-4 inches of travel)
165-420

Stock rear (1-4 inches of travel)
240-420

KW Rear (1-3inches of travel)
260-360
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      07-12-2012, 07:58 AM   #3
Kgolf31
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Much appreciated. I can't believe I couldn't find it still.

Thanks!
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      07-12-2012, 10:29 AM   #4
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It's hard to find to be honest. I only found it because I used google and z4m kw v3 spring rates as my search parameter. Won't find it otherwise. Did the search a long time ago. cheers!
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      07-13-2012, 04:12 PM   #5
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I'm not sure that you've actually identified the OEM spring rates by using KW springs to deduce the information.

I've obtained the spring rates directly from Eibach of their lowering springs for the Z4MC and they are approximately 15% stiffer than OEM and are as follows:
Front: Progressive spring, initial rate is 23N/mm (131 lbs/in) and the end rate is 34N/mm (194 lbs/in)
Rear: Progressive spring, initial rate is 70N/mm (399 lbs/in) with the end rate of 140N/mm. (799 lbs/in)
Most aftermarket adjustable suspension kits for the Z4MC have front spring rates in the region of 400 lbs/in and rear spring rates in the vicinity of 550 lbs/in, so the OEM front to rear sporing rate ratio is completely different with the OEM set up.
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