Suspension Options

[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. :(

[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]

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]

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]

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]

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.

[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.

[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.

[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.

[nmlss2006]

Oh yes: from the old e30m3 page, the wheel rates are x0.88 F and x0.45 R.
We therefore have:
106 / 245 stock 325i -> 93.3/110.25, 84.6% F/R ratio
180/380 H&R sport -> 158.4/171, 92.6% F/R (so front is stiffer, in proportion -> more understeer, all else being equal), ~55% stiffer than stock
315/570 H&R race -> 277.2/256.5, 108% F/R (even stiffer in the front -> more understeer still), 132% stiffer than stock
I suspect the relative stiffening in the front goes with the fact that swaybars tend to become a lot stiffer in the rear and not quite as much in the front, one goes from 20/12mm to 22 (+10%)/ 19 (+58%!) or even 25/22. That probably balances out the F/R ratios.
With all this being said, if we assume that the 30-35mm drop of H&Rs more or less halves useful suspension travel, the spring rate has to double: therefore, 106/245 -> 212 F 490R. That would come out to 186.6 / 220.5 effective wheel rates, which is.. well. Not soft :). That would require a LOT of damping from the shocks and nice and stiff sidewalls.

[nando]

maybe you're not accounting for wheel rate - that 500# spring in the back is actually only about 250# when you consider wheel rate. the front isn't as big of a factor but it's still there. also consider how tall and soft the typical suspension from the 1980's was. remember they had just come from an era of giant floaty sedans - just think of any 1970's chase movie where the cars barely make a corner with about 20 degrees of roll.

I think you would be challenged to find anyone running a linear spring with a rate of 250 lb/in. the H&R sport front springs for my ix were 220#, and that was far too soft for the height. most kits like GC start at 450# which is even considered fairly soft.

[nmlss2006]

Bringing this back up - Nando, the text IS divided in paragraphs :). In any case, if you are correct and there's 1.5ins - that is, less than 40mm - of travel left in the suspension then lowering the car 35mm with the H&R is lunacy: per what I was saying above and if we pretend to ignore a few things, we'd have to go to 2x stiffness, give or take, since we eliminated ~50% of the travel. In that case you and Jean would be 100% correct, the springs are way too soft. That surprises me because it would imply that a stock E30 from the factory has <3" of travel on the suspension. That's not very much at all - think 'a 911 has more'.
Jean, I hear you, but then the question becomes, what does one put in? Going to 250 lb/in front and 500 rear on a car that weighs less than 1300kg seems... excessive to say the least.

[Aciid]

Kyb/vogtland springs ftw. I just put this combo in my car, dropped it 1.6" front and rear and I am loving it! The ride is good and it looks awesome. I'll be posting pics of my car up soon when I get my new wheels on, so until then I'm rocking bottlecaps.

[Jean]

nmlss2006 - I've had about 5 suspensions on the e30 alone, and I can honestly say h&r sports with bilstein sports were one of the worts combos I've had. I put a lot of miles on the car, smooth roads, bumpy roads etc. All of these changes were done leaving the tire aspect ratio the same, so I didn't change 10 things at once ;)

[nando]

Nando, FFS, I wrote: 'If roads are awful, I'd stay with the Konis and put on H&R sports. that is already over 50% stiffer than stock: anything else will help if you are VERY smooth in a track setting with good paving and hamper otherwise'.
So you are entirely correct: people who track their cars exclusively have very different requirements. And by the by, while you are also entirely correct that poor damping will worsen performance (and indeed, most cars stock and otherwise are undershocked more than they are underspringed), if you INCREASE the damping rate of the shocks to where it's correct for the springs you will FURTHER LIMIT suspension travel - which is great in any situation... but it won't help if you need that suspension travel to copy the road or, God forbid, to help absorb the weight transfer of a mistake/correction/what have you.
And, I believe the OP was talking about 'poor US roads'. With the roads I've seen in the US, you WILL get poor tire contact with H&R races or IE3s, unless the 'poor roads' he's talking about are significantly better than here, especially if you couple them with shocks that can actually take an effective wheel rate of 570x0.45 = 256 lb/in. There is no way around it folks: if the surface is uneven you need compliance until physics changes. If you want controllable reactions you want the springs to absorb energy instead of transmitting them to the tires, doubly so on uneven surfaces. Yes, on DTM circuits it makes perfect sense to have 900 lb/in springs *if you're a professional*. The problem is, none of us are professionals, we're not racing in our DDs and even the circuits here (In the NE, I suspect the others aren't any better) have MUCH worse paving jobs. The roads are best left unmentioned (PA and NY take the cake around here, I'm sure there are areas in other states that are even worse).
Just to mention an example of what happens *even with a professional at the wheel*, go look on Youtube for a now-infamous video of a person driving a FXX at Rijeka. The paving there is significantly worse than at other european tracks, not as bad as, say, jefferson @ summit point and he is spending most of his time trying to keep the car on the road, not going fast, because his sidewalls and suspension are too stiff to go fast.
Jean, by the by, if the H&R sports are indeed too soft for their drop, which is something *I haven't personally experienced* but I admit my experience is limited to OE sports, which have about 0.3" less drop, increasing shock stiffness may help. I am surprised that noone (and I do mean noone, I asked TC Kline, Turner, etc) has stock vs. koni vs. Bilstein damping diagrams. With those and a somewhat serious investigation on effective travel of the suspension (again: noone knows how many MM of travel you have from stock BMW riding height to bump stop contact and/or to bottoming out without bump stops?) we can start talking quantitatively about damping Nm vs spring Nm. Let's also keep in mind that an E30 weighs 1300kg on a fat day so forces will be different than what they would be for a 1600kg E90 or 911.
On top of all this, noone has been talking about tires, which I believe I mentioned earlier: using 250 lb/in (44N/mm) spring rates on 126mm sidewalls is again not what I would call particularly well matched.
balooetc, apart from the above, I suggested 21/14.5 swaybars, not 22/19, in my comment but I allowed for 22/19 because I know that many, as yourself, cannot quite mentally decouple roll from actual effectiveness despite physics, unfortunately, working the way it does, so you will have more fun, tuis verbis, with a car that rolls less despite any actual loss of performance. Besides which, if it is true that increasing the effective spring rate is a benefit as you maintain, I would say that my comment is anything but stupid - not that I find the qualification entirely justified but I've given up a long time ago on civilised conversation in forums.
To sum my point of view up: I will, in the next few months, acquire more experience with H&R sports on a 6 cyl car and it may very well be that you are correct and H&R sports + bilsteins are not as good a match as I think though the numbers seem reasonable to me - I will be running Koni SAs however: Bilstieins, according to the people who make them, have a VERY steep compression curve to compensate for reduced travel. I would find it very, very surprising if this, however, meant that going to H&R Race's 315/570 rates vs 118/265 stock (that's over 200% stiffer!) with bars that are stiffer on top of that were the best approach for a car to be driven *on poor roads i.e. not on a track* as the OP asked.
OP, sorry for the threadjack.

wow, while I'd like to read that and post a reply, I just can't. paragraphs?

I don't "exclusively" track my car, either. and I *know* my ride quality improved with stiffer springs over the ultra-soft H&Rs, so you don't have to argue about it. I have a good idea how much travel I had with H&Rs - about an inch and a half with stock bump stops. that isn't very much. Handling isn't any better with soft springs that bottom out, in fact bottoming out is far worse.