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      09-01-2019, 05:41 PM   #1
DrPancakes
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KW V3 Conversion Question

Hi all,

I actually own a F30, but intend to do a KW V3 conversion. Unfortunately, there's not a lot of threads on this in the F30 forums. For those who have done the conversion, mind sharing your insight?

On the E90/E92 forums, one of the conversion kits (I'm assuming from HP Autosports) comes with shorter 7" Swift Springs in the front - 2 inches shorter than the KW V3 springs for the E9x. Is there any reason to get shorter springs in front? Wouldn't you lose some suspension travel and then need a helper spring to keep the spring on the perch during suspension droop?

https://www.m3post.com/forums/showth...=kw+conversion

For the F30 330i V3s that I'm buying, I was told by KW the front springs are 242 mm (~9.5") and the rears are 200 mm (~7.9" not including the helper spring). Would 9" front springs be sufficient, or would I need helper springs? For the rears, should I go 8" and use the helper spring? Would I risk popping out the spring while driving with a 9" spring?

For spring rates, it looks like the E9x and F3x setups are similar (springs are separate from the shocks in the back). Is there any guiding principle for the ratio between the front and back, as well as what is a firm but acceptable daily driver spring rate? For example, is there a spring rate cutoff that would make me spill coffee while driving? This is my daily driver, but I only put on ~5000 miles a year and intend to go to 5+ HPDEs a year. I was originally thinking of 6 or 7 kg/mm (336 or 392 lbs/inch) in the front and 13 to 14 kg (728 or 784 lbs) in the back, but I really don't have any experience to compare to.
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      09-08-2019, 09:13 AM   #2
slicer
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Why are you wanting to replace the springs?

The reason I ask is that the V3 is a street setup with progressive springs. The only motivation I could imagine to swap to linear springs is for track use. At that point I would get a more track oriented suspension. Such as the KW club sport. Don't waste your time and money fiddling with the V3's.

Regarding spring length - the minimum length spring depends on your ride height and the actual spring travel of the spring. Spring travel can vary for the same length spring. You need to look at the specs. You need to be sure that the shock will run out of travel on the bump stops before the spring runs out of travel. A spring hitting bottom is metal on metal.
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Last edited by slicer; 09-08-2019 at 09:47 AM..
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