Hi everyone, sorry to bump an old thread but it seemed to be the most relevant to my question, so I figured I would give it a try.
I rallycross my 98 M3/4/5, and I need some advice about what to do with my spring rates when I remove both sway bars. The car is on JVAB offroad Bilstein-based shocks, and has/had stock sway bars. Front springs are 12" 250 lb, rears are 7" 350 lb (although I'm probably going to try and squeeze some 8" springs in there). I recently removed my FSB in an effort to get rid of understeer when on course (it helped), and I think I would like to also remove the rear to help me put down power and get better wheel articulation. I believe that I will need to raise my spring rates to compensate for the lack of sway bars, but I'm not an engineer and can't calculate how much I should change. If I had to guess, I would start with 300f/400r, but it's just a guess. Can anyone comment on how I should go about this? I can't exactly buy a bunch of different springs and try them all out, because that would be too expensive on my tight budget.
Thanks in advance!
One of the reason you are not getting much response is because what you are asking doesn't have a\ simple answer. Figure out the roll couple for the front axle. Figure out the roll couple for the rear axle. Determine what roll couple distribution you want for your off road endeavours (I gots no clue on this one). Do a bit of light math.
/.randy
I went through the same questions a while ago on FrankenCoupe. The rear bar is off, and I just can't get the level of front grip I really want. Part of my problem is that I refuse to run a splitter do to the hassle of trailer loads. I tried more bar, for sure that was not a surprise and lost a few seconds. I tried removing the front bar. It resulted in loss of feel and just a mushy feel that netted less than the stock bar. I raised the rear spring rate and that improved things a bit, including a little less front wheel lift. I still have too much. I've come to the conclusion I have personally reached the limit of the shock hardware relative to the car as is, and either plunk down 4 to 6k for better tubes or just stop chasing the holly grail and enjoy the ride as is. Given I now only go out 3 or 4 times a year, I've come tot he conclusion, there are other things to piss away my hard earned cash on. All this to say, you just have to experiment and test. dream/guess/try, repeat.
Dan "PbFut" Rose
I can update my storyline....I ended up going straight to a 700lb spring, and am so much happier. The front and rear suspension now feel like they're well matched, as opposed to being stiff but not overly so in the front, and completely squishy in the back. I would strongly recommend not going lighter than 500lbs or so in the rear (and even that is too light for my taste), and this is coming from someone who has no desire to have a stiff or jarring ride.
2001 Z3 3.0 Coupe--Sterling Gray/Sunroof Delete/5MT
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