Suspension Options

[nando]

people tend to put WAY too big swaybars in the rear. the people who know better run stock or even none at all.

220# is a lot softer than you think. how else do you think guys get away with 500-700# rates, or higher? my 600# springs are about 5x stiffer than stock. you can do 500# springs with the same bilsteins or konis that people use with stock or sport springs.

[JeffRR]

A better method of comparing set-ups is to look at ride frequency, there is a pretty good discussion on ride Fn in this thread:

http://www.r3vlimited.com/board/showthread.php?t=95373&highlight=ride+frequency

Don't fear the stiff springs, you can run much stiffer spring than what you'd imagine. 2hz Fn isn't too bad if you keep it from bottoming.

The majority of ride complaints on lowered "sport" suspensions is bottoming. Oh ya the baseline bilstein sports were valved for stock ride height, same goes for the baseline Koni SA's.

[nmlss2006]

Nando: a 570 spring will give you 220 at the wheel, as I was saying. As to shocks, there is the other problem: if the koni works with 380 rears (H&R sports, etc), it won't work with a spring that's 50% stiffer, 570 (H&R race). Doubly so for the bilstein, which won't even let you adjust extension. One can argue that it will sort of manage both, but there's a lot of 'sort of' in a 50% change in spring rate. Most cars need more shock more than they need more spring, starting from a stock-BMW situation. And there's always that sidewall that gets in the way...
Oh and Nando I agree about the bars too, mind - but running NO bar in the rear should tell you something about your spring rate :).
JeffRR, reading, will report back.

[nmlss2006]

Jeff, what I get from that thread is that even with Koni SAs, which I suspect are significantly too soft for those spring rates, the suspension he quoted - 500/700 - was too stiff to run *at the track*, to the point where removing the rear bar had an immediate advantage in grip, without even having to go into too fast transition times.
I am having a very hard time figuring out how this equates to that stiff a spring being a good idea with a rear sway bar on the street, with a significantly worse surface. Again, without even going into the driver skill required to control the transition times you'll get with that setup.

[nando]

konis seem to work fine up to about 700#. you can also have them revalved (bilsteins too), or if you buy them new with your springs, matched. It's not that big of a deal. There are thousands of E30s running springs far stiffer than stock, and there have been for decades.

[nmlss2006]

Yes: there also have been E30s running H&R springs since when the cars were new, but everyone here seems to agree that that's a terrible idea :). Yes, you can certainly have the valve rates matched and that makes that work, but it's the first time it gets mentioned in the whole thread.
The point I was trying to make is, if we're going to argue vehicle dynamics, let's at least agree on the fact that having a 50% disparity between shock rate and spring rate is materially suboptimal.

[nando]

where did you pull that # from though? the shocks can work over a range of spring rates. Otherwise you'd have to revalve them for even a minor change in rates. a perfect match may be best, but we're talking cars that are mostly worth under $3k.

basically the important thing is rebound - if your suspension isn't bouncy with the stiffer springs, your shocks are fine. and hey, konis are even rebound adjustable! ;)

[nmlss2006]

The number? From H&R sports to H&R races. The races are ~50% stiffer but people will run Bilstein sports with both and 'be happy'.
And I agree, we're talking cars that are worth under $3k... in many cases, but I thought the discussion had progressed a bit from there. And if we progress from there, yes, adjustable rebound will help, but no shock will be able to take a 50% variation well. See, if you have the correct shock for your spring rate, you can use a softer spring. Shocks are not only about controlling rebound :). That's why I mentioned that a lot of BMWs, stock, are undershocked: if you can persuade someone to sell you shocks that are valved right, even an E60 on stock springs can surprise a lot of people. A friend with a 535d does precisely that on a regular basis.
I think, by the by, therein lies most of our disagreement: I would rather have firmer shocks and softer springs, comparatively, with a decent amount of bar but nothing excessive (I have Dinan 22/16s on one of my E30s, I happen to like that a lot, with the relatively soft Dinan springs and Koni SAs, M3 fitment, set halfway, so 'quite a lot of shock' for the spring).
Others - you included I think? - prefer firmer springs, less shock. I think we're entering the realm of personal preference though.
To conclude: I'll try the H&R sports with Bilsteins as soon as I get this other car out of the garage. I have to find wheels for it though, bottlecaps with 195/70 M+Ss from 1993 may not be the most appropriate.

[nando]

no, I prefer a proper amount of rebound for a stiffer spring, good travel, and less swaybar. I did win in SM at the local level a couple years ago, too bad I haven't been able to get out much at all since then. :(