Ok so I now have the Adjustable Koni's......

[Boom n Zoom]

The fronts have now been in for a week along with new lower control arms (alloy) and stock upper strut mounts (No negative camber than stock)
It all feels so much better that the CD player has stopped skipping (Yay!) except over really bad expansion joints (one bridge in particular is really bad) The suspension guys (Fulcrum Suspensions) set the fronts at one and a half turns up from the softest setting, it was a little jarring so I have backed it off to a half turn from the softest position. This is twofold as it will allow the front suspension to 'settle in' and it stops highlighting the fact that the rears are shot :), lots of bouncy bouncy and a not inconsiderable amount of squat when you get hard on the gas.

So onto my question, I picked up the rears today and I plan (best laid plans and all that) to fit them in the next couple of days. My question goes out to the guys who have the Koni adjustable/Eibach Sport spring setup. This is not to discount any other opinions and or useful information that other members here may have.

I ultimately would like to minimise the squat, but as the compression (within the shock) is preset is there a good rule of thumb for the rebound setting? I have done numerous searches here and web wide and I can find numerous mentions that the Koni/Eibach setup is great but no real guidelines as to the rebound settings that would be suitable.

More importantly how does rebound affect the handling of the car?

Does rebound help to control the attitude of the car i.e. Driver inputs, steering, braking, accelerating?
Or does it control the balance of the car over rough surfaces?

I am just a little confused as to what effect rebound damping adjustability has on the cornering, braking and accelerating inputs, especially if one is say at a track day. :D

I understand that many people like varying degrees of 'firmness' I personally don't mind firm, but I have to consider the other occupants of the car. With the front's set at the half turn up from the softest setting it is a nice ride, (way better than before) I am getting much more feedback through the wheel than before and it turn's in, holds and can change line with a great deal of precision over average road surfaces, so I will leave the fronts for now.

The problem is that the rears you cannot get to once they are fitted into the car. I would like to hear opinions/experiences that others have had on the settings as I would like to minimise having to take them in and out to get a nice 'compromise' setting. This is not to say that I won't be pulling them to 'tweak' but if I can get close to the mark, with help :) then I won't be chasing around all over the place.

It also comes back to an understanding of what changes to the handling of the car very high or low rebound settings will have. My guess is that if you have a far to stiff rebound setting that this will induce power oversteer and that too soft will induce power understeer?

Thanks for reading this far, if you made it........ I will keep on searching for an understanding of rebound settings and the effect they have on the car.

Cheers! :)

[Mr Project]

Well, I have the Koni/Eibach combo on my car, but it's a 535i Touring, which changes things a bit in terms of weight distribution compared to a 540 sedan.

I can relate 100% on your comments about the front. I've done the same thing, started with 1 and 1/2, ranged from 2 turns in from soft, to 1/2 turn in currently in 'soft commuter' mode. 1/2 turn IMO is right on the edge of not being enough rebound dampening to keep up with the spring rate.

I also have 1 and 1/2 turns in from soft in the rear. On the Touring, this has been OK, but it has bottomed out with 2 heavy rear passengers when driving (very) hard over rough terrain. I wish it was easier to adjust so that I could put in an extra turn or so when I have big passengers or a heavy load...guess that LAD I tossed out had a purpose after all, eh? :) The ride quality actually gets much better with passengers aboard. This leads me to believe that I have a bit too much compression damping for the spring rates, especially in the rear, when I'm not carrying a load.


One important note: I'm pretty sure the Koni Yellows adjust rebound and compression simultaineously, don't they? I didn't think the Yellows were a rebound-only adjustment. If I'm all wet, let me know.

[Qube]

Any other non-Touring 535s with Konis? I'd like to get a ballpark (though difficult with different springs) for rears. Once they're in, it will be a pain to adjust the rear.

[TC535i]

Well, I have the Koni/Eibach combo on my car, but it's a 535i Touring, which changes things a bit in terms of weight distribution compared to a 540 sedan.

I can relate 100% on your comments about the front. I've done the same thing, started with 1 and 1/2, ranged from 2 turns in from soft, to 1/2 turn in currently in 'soft commuter' mode. 1/2 turn IMO is right on the edge of not being enough rebound dampening to keep up with the spring rate.

I also have 1 and 1/2 turns in from soft in the rear. On the Touring, this has been OK, but it has bottomed out with 2 heavy rear passengers when driving (very) hard over rough terrain. I wish it was easier to adjust so that I could put in an extra turn or so when I have big passengers or a heavy load...guess that LAD I tossed out had a purpose after all, eh? :) The ride quality actually gets much better with passengers aboard. This leads me to believe that I have a bit too much compression damping for the spring rates, especially in the rear, when I'm not carrying a load.


One important note: I'm pretty sure the Koni Yellows adjust rebound and compression simultaineously, don't they? I didn't think the Yellows were a rebound-only adjustment. If I'm all wet, let me know.

Nah, just single adjustable. Double adjustable is signifigantly more expensive, usually require more frequent repair/servicing, and the gains are insignifigant on a street car.

[Mr Project]

Nah, just single adjustable. Double adjustable is signifigantly more expensive, usually require more frequent repair/servicing, and the gains are insignifigant on a street car.

I understand that it's single adjustable, but I thought that single adjustment ramped both rebound and compression together. Maybe I'm thinking of Tokico's single adjust struts. Too many different ones over the years. Can somebody confirm?

[TC535i]

I understand that it's single adjustable, but I thought that single adjustment ramped both rebound and compression together. Maybe I'm thinking of Tokico's single adjust struts. Too many different ones over the years. Can somebody confirm?
I see what you're saying... I'm not sure.

[Boom n Zoom]

Much appreciated, I think from having found some info on set-ups for e34's (mostly M5's) but reading it all it seems to translate to the rest of the e34 5 series range.

It appears that most of the set-ups call for stiffer rear enhanced by a stiffer rear sway bar. This will reduce the understeer tendancy of the platform in stock trim. Once you lower the CofG with springs it is reduced but the most significant improvement is as above.

I still haven't come across what effects harder or softer rebound alone front or rear will have, I'll keep searching :)



I understand that it's single adjustable, but I thought that single adjustment ramped both rebound and compression together. Maybe I'm thinking of Tokico's single adjust struts. Too many different ones over the years. Can somebody confirm?


It appears to be only the rebound that is adjustable, I called the Suspension shop and asked. They confirmed that the Koni yellow sport 'adjustables' are rebound only. They do have different compression valving for different models which is borne out when you order them. (differing part numbers)

It seems though that the M60 3 or 4 litre V8 is very close in weight to the 3.5 I6, so a similar setting could be used with fine tuning to suit.

Cheers!

[Qube]

Thanks for your insight. There is actually a recommended setting start point in the installation guide, but I don't have it with me. I'll keep in mind the stiffer rear though.

[Mr Project]

Much appreciated, I think from having found some info on set-ups for e34's (mostly M5's) but reading it all it seems to translate to the rest of the e34 5 series range.

It appears that most of the set-ups call for stiffer rear enhanced by a stiffer rear sway bar. This will reduce the understeer tendancy of the platform in stock trim. Once you lower the CofG with springs it is reduced but the most significant improvement is as above.

I still haven't come across what effects harder or softer rebound alone front or rear will have, I'll keep searching :)



I'll just fill in my limited experience here:

Car 1 -
535i Sedan
25/19mm M5T swaybars
Stock springs/shocks (worn)

Car 2 -
535i Touring
25/19mm M5T swaybars
Koni shocks/Eibach springs/3mm spring pads (1.5 turns front, 1.5 turns rear)
New dogbones

With the same wheels and tires, the sedan was actually much MORE prone to oversteer. The Touring just sticks and sticks in the same corners and speeds where the sedan would start to step out. The Touring will understeer gently in high speed sweepers, and can be coerced into oversteer, but only when the throttle is absolutely abused with weight transferred to the front.

Now, so far I've only made changes to the front shocks on the Touring. Of course, the most obvious change is ride quality from the front end:

Full soft - Becomes bouncy and clearly the shocks are not able to keep up with the spring rate. Turn in is 'soft'.

1/2 turn - Better turn-in, much less bouncy than full-soft. Still able to generate some oversteer with effort.

1.5 turns - Even sharper turn-in, better body control, ride 'crustier', maybe slightly more grip from the front end...but I would say a slightly reduced ability to generate oversteer on command.

2 turns - Excellent turn-in, good communication from the front end, obviously ride quality suffers even more. I would say that actually high-speed understeer becomes the worst here, but I ended up putting 4 psi more in the rear tires and that REALLY balanced the chassis back out. Enabled oversteer once again, and I got to keep the nice sharp turn-in and tight body and weight transfer control. This was a GREAT setting for going really hard at the mountain roads in SD.




It appears to be only the rebound that is adjustable, I called the Suspension shop and asked. They confirmed that the Koni yellow sport 'adjustables' are rebound only. They do have different compression valving for different models which is borne out when you order them. (differing part numbers)


Yeah, I read up on Koni's site as well and it looks like that is correct. Only the rebound is adjusted. Sorry to take this off-track, I'm obviously confusing them with different shocks.

[Incantation]

i like the dual outlets in the back.. looks fuken sick.

[Boom n Zoom]

/Cap in Hand,

Firstly, I would like to apologise for having dragged this to the top after it has made page two, but I need to follow up :)




Thank you very much for your information.

Mr Project, your 'limited experience' (pfft! yeah right, it was brilliant!) was very helpful and I thank for taking the time to write it up.

I set the rears at 1.5 turns, let them bleed down for a half hour then moved them through two full strokes. The 'nominated' right side was rebounding at a fair rate of 30 seconds from full compressed to the full extension. The 'nominated' left side was taking 55 +/- 3 secs to return from the same test.

I then rechecked to make sure that I had both sides set to the same 1.5 turns. All checked out, rerun the test, return the same results as before.

I then decided to see how many turns of adjustment there was with each shock. The 'right' side has 3 and 3/4 turns from full soft to full hard, the 'Left' side only 3 1/4 so there was a half turn discrepency in the adjustability of the valving. I checked part numbers to make sure, all good.

In the end (this was at 11:00pm local GMT + 10) I adjusted the 'left' to match the 'right' rebound time on the test as before and then fitted up both sides. Had it completed at just before 01:00. So the setup is 'about' 1.5 turns, I suggest that anyone fitting the adjustable Koni's, check once you have them set to make sure that you are getting a similar rebound rate, a possible trap for young and old players alike.

Anyhow, on the drive today, burbled through the northern suburbs checked the tyres 270 Kpa front and 290 Kpa rear, filled up (67 Litres of BP Ultimate @ $1.24/Litre) It feels very firm, but all new shocks will do that until they have settled in, the full tank of fuel helps.
Gassed it hard in S3 mode from the service station to avoid being T'Boned or rear ended, it has virtually no squat, it just hooks up and launches (ETC off) I pull up at the lights 150m ahead then wafting through the sunroof is that burning rubber smell, Hmmm the rears spun for the first time with a full tank.....this could be v..e..r..y interesting.

It has transformed the handleing of the car, yes the ride is a little harsh on the goattracks we have here that pass for suburban roads, but not that bad that I feel the need to pull them out and reset them. I expect that once the rears have settled down it will still be firm but not 'crusty' ;)

The Highway is a different matter, it is brilliant!! It doesn't wallow anymore it just sucks up the imperfections yet the ride is taut without being nasty.
I am really impressed! :)
I am looking forward to the opportunity to get to a track day and play with the Front settings and tyre pressures to have a 'city commute' setting and a 'Play at the track' setting.

Again Thank you all for you information.

P.S. I have taken some pictures of the Quad tip zorst and how it is done. I will post them sometime soon for all to have a look at, prod, poke and snicker :D

Cheers!!

[Mr Project]

No apologies needed, always good to hear the results of a thread from the OP.

Your idea to time the rebound was very good, I wish now I had done the same! I used an untimed method of the same just to make sure I was adjusting them in the right direction, but I didn't think to check for parity between the two units. Hopefully the next person will read this before doing the install!

Glad you're enjoying your new suspension!