Quote:
Originally Posted by bbnks2
So, where is all this good information that you can provide in response to the op? Did you even read the thread?
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There's a littany of information all around the internet about target suspension frequencies for balance.
I ran the car on several different rates. I started with 400/850 w/stock rear bar and a reasonable front (27mm adjustable). It was such horrific push I can't possibly describe. Those who aren't experiencing it are simply underdriving the car, period. Kyle warned me about it when I mentioned wanting to try it (he ended up at 400/700 with a 19mm rear bar and slightly softer front than me), but it was still there, very badly. I switched to 575/1200 (because the car was rolling well out of its camber curve up front as well), and went to a 20mm rear bar). It was much, much better. I've switched shocks and don't campaign the car very much anymore. I'm at 450/850 with a 20mm rear bar and 27mm front bar.
Even at 575/1200, the car rolls a LOT because of how bad the motion ratio is in the back, it's hardly any wheel rate at all. The stock spring rates for the car are biased nearly 3x (160/420). Yet it still pushes pretty badly. Just adding a mountain of camber does not solve this. It's a wheel rate of 150/135, because of the motion ratio. I would use as a starting point a similar wheel rate target if you want to keep the stock rear bar. So, starting with a 400lb spring, you're looking for a wheel rate of around 320lbs, or a 1000lb spring. Of course, after going to a larger front bar, you'll want to add the requisite rear rate to compensate for it. I ran the numbers to keep my balance on 450 fronts with a stock rear bar, and it required (I think) around a 1350lb spring. That's why people add bar / run a lot of spring. Look up the OEM M3 rear sway bar size and you'll see that a lot of the justification on here makes very little sense unless you're keeping the open diff. It's substantially larger than what either of us ran.