Damper ratings for stock setup

[DJAM3]

Yeah at 104k miles I'm pretty sure the original dampers are dead.

[liam821]

I have ground-control coilover sleeves with custom rate shortened Bilstein shocks on my race car. I purchase my Bilstein dampers separately since I wanted specific things done to them so I only ordered the GC coilover pieces/top hats from GC. Their top mounts/hardware is solid and well built. The street camber plates that kit you are looking at are very quiet and streetable, I had them on my last e46m3 street car. I've never been a huge Koni shock fan, I like how monotube damper performs (such as the Bilstein), but a lot of people really like the Konis and I can't really say anything bad about them.

Like a bunch of other people have mentioned, I would not just take their recommendation on spring-rates and do some homework on what you're looking for. You should reply here with what they recommended - I'm sure you'll get some feedback.

It's interesting you feel that you don't have any suspension travel. It's possible the shocks are just so worn out that they're constantly crashing into the bump stops. I run a pretty aggressive ride height in my street car and still have loads of suspension travel.

[sharadn]

No leaks on original shocks with 105k do not mean they are functioning properly. Remove those shocks and I would bet there is very little resistance in either direction of travel (whereas there should be, increasingly so on rebound).

I have one strut out and it has resistance in both directions so it is not completely shot. It is as you described above. The shocks and struts are virtually never hitting the bump stops, they just never make that much travel. It seems that the setup is just to hard to ever get to the bump stops.
I get it that the whole suspension thing is very subjective and it can be a real rabbit hole. I do think that I should be able to see some improvement but don't want to buy something that does not at least move me in the direction I want to go. I guess I need to do more research before I make a purchase but I do appreciate the knowledgeable input from all you forum members and your willingness to help me sort it out.
Aside from coilovers it seems that two most promising options are the Koni sports or the Bilstein B6. Can anyone comment on the difference between the M3 stock setup and the ZHP setup? Is the ZHP level of stiffenes a reasonable target as I mentioned in my question to Ground Control? It seems that it is somewhere between the M3 and a non-M setup with regards to stiffness.

[JamesSJ1]

As a reference point, I did a nearly full suspension refresh on my 2006 vert a year ago at 90k miles and chose Bilstein B6 with stock springs. My rear shocks were weak at best, though no leaks on anything front or rear. B6 is not more supple in day-to-day operation, and I've had the car since 2015 at 30k miles so I have a pretty good sense of how it felt when I got it from the previous garage queen owner, through my daily driver years.

The suspension feels more planted on bigger suspension movements, like larger rolling peaks and valleys in the road, and hard cornering. There is just a different feel to how it handles the larger movements than stock, and I like it better. Small bumps and ruts on the road are not improved, and with almost all the rubber movement components changed (still have FCAs to do soon) that doesn't lead to the B6 being the choice for what you're looking for. I think the Koni Yellows with stock springs might have been a better choice even for me (and you) since they have adjustable dampening. Perhaps that will take up the smaller, quick movements that bumps/ruts in the road cause. For the spring side of things, the 'vert spring rates are different than the coupes, but doesn't seem like you're looking for lowering springs so that probably isn't an issue. If you throw a lowering spring kit on the 'vert, they're almost all made for the coupes so it just won't sit right. At the least, I think it needs a little firmer spring in the rear because the 'verts have extra weight there. Still wouldn't be surprised if there were more ideal spring rates for the 'vert, maybe something that FatCat Motorsports or the like could figure out for a fee.

[sharadn]

this just came in from Ground Control:
"It will be around 450 up front and a 550 in the rear, unless you have specific rates you want us to do"
Seems high considering the stock fronts are 143.

[sharadn]

I am thinking the probably my best approach is to just use the stock springs with the Koni sports. It seems that all the other options are going towards additional stiffness

[Tbonem3]

The 440/550 is what GC slaps on every kit that isn't for the track. You would not be happy. Stock springs and Konis on full soft will be good. I still don't know your current stock setup is too stiff. I just bought a 123k original car and the suspension actually feels great! Just massive wheel gap/body roll, but still composed and tight, but plush.

Maybe you should get the 440/550 kit, then go back to your stock setup and you'll be happy

[sharadn]

I don't know what is up with mine but it is definitely not plush and there is little to no body roll on turns. I guess if I buy the GC kit and it makes me like my current setup it will have been worth it (at least for GC)

[sharadn]

Latest from GC:
I just talked to a tech and they said we will actually set you up with a 375 up front and close to a 450 in back. He said that will put you really close to a "zhp" ride quality spring wise and it will have better valving.

[r4dr]

Latest from GC:
I just talked to a tech and they said we will actually set you up with a 375 up front and close to a 450 in back. He said that will put you really close to a "zhp" ride quality spring wise and it will have better valving.

That still puts you in pitch territory for the ratio of bounce frequencies front/rear (0.84 in this case). Something like 225/450 (1.08 ratio, flat ride) would be my preference. That being said, GC valving still doesn't have a reputation for being the softest -- TCK is also Koni-based but allegedly their valving is better in that category. But I have no personal experience with TCK.

I really think you would be happy with just stock springs & fresh Koni Yellow dampers. Make sure to get new hardware so that your new dampers aren't handicapped by aged out rubber and etc.

[sharadn]

Do the Konis ever go on sale?

[r4dr]

Do the Konis ever go on sale?

Yes. I know Bimmerworld had a good deal on them within the past few months. But they're harder to price shop than Bilsteins for whatever reason.

[sharadn]

Tire rack has a complete set for $750 and there is a set on Ebay for $745.95. I am not in a hurry so if would see a sale coming up sometime in the future I would wait

[Tbonem3]

Koni usually does a spring sale.

[sharadn]

Thanks