KW v3 rear springs compressed/sagging

[taranfx]

I was wondering why rear felt stiffer than front. This could be the reason.
Does anyone have similar experience? Do i need to replace my springs or is it wrong installation?

[taranfx]

Bu p. Anyone?

[KennyP]

You are still having problems? i think i read some time ago that you found a solution...

Went and took a picture of my rear spring so you can compare. Its a bit dirty. Its winter season afterall at the moment.

My suspension sagged over time. More in the back and less in the front. Few weeks ago when had new brakes and rear bearings installed i had my ride height raised: 5mm in the front and 10mm in the back... Now my ride height has same proportions as i initally had it set up: rear is 5mm higher than the front (measured from wheel center to arch. After raising the suspension i did notice that my rear suspension is now a bit more forgiving.

On your second picture it seems like purple adjustment collar is wrong. It should be above the spring, not between springs spiral/winding. Spring should be sitting on that purple collar.

[proboner]

It's a design flaw... I'm convinced KW just phoned in the design for the E89. KW advertises progressive spring rates, which is a great idea, except the way the build adjustment into the front coil over(by compressing the spring, instead of shortening/lengthening the strut tube), the softer coils get compressed out and it just becomes a stiff static rate. Same thing in the rear, except now your just bouncing on less than an inch of spring movement.

[KennyP]

I dont think it is a design flaw...KW does talk alot about testing and developing their suspensions on a rare 7post driving dynamics test rig.
Yes it is a bit stiffer than stock but i think mine still rides pretty nice. Its not like im driving on stilts. Low sportcars cant be as comfortable as luxury sedans.
Just dont totally slam the ride height and use softer settings. You cant have everything with suspension... its either comfortable or sporty. By lowering you reduce the amount of travel suspension can have. It cant be the same as it was when stock or it would rub. And this results in stiffer suspension.
And these compressed coils are probably there for times when suspension becomes unweighted like during jumps or going over a crest at speed. Spring needs its travel at these situations too and cant just flop around being too short uncompressed.

Progressive springs are awesome for road use. On track maybe you want fixed rate springs. Z4 with these KWs is the 3rd car i have had with progressive springs. Two previous had lowering spring kits installed. 04 Type R had TEIN spring kit and they were great.Right amount of stiffness while still comfortable enough to not feel every crack in the road. Sadly i crashed that car on a twisty country road by rolling it after getting into a tankslapper. On 07 Type-R i installed Eibach Pro kit lowering springs. These i hated. Too soft and not sporty enough for me i guess. Too everyday... Was not a fan. KW feels like its between Tein and Eibach. Less suspension travel in the Z4 though. Its great over small stuff but on big bumps it does get real stiff because i guess it just runs out of travel and bottoms out.

[proboner]

Ugh, I just wrote an entire response and it's been deleted. Long story short, I disagree with most of the things you've said here. List of grievances:
- 3 dead rear coils. There is no reason for this
- No strut sleeve height adjustment
- Adjusting height with the spring perch causes lower spring rates as the car goes lower and higher rates as you raise the car. As you've pointed out, this is the opposite of what it should be
- Adjusting height with spring perch pushes the front shock out of it's optimal operating range as you lower the car
- Shock valving, IMO, is too harsh and rebound adjustment is hardly noticeable. This of course pertains to the ST XA (KW V2) setup I'm running, which theoretically should be less aggressive than the V3.

[KennyP]

http://int.kw-suspension.com/int/kw_productrange.php



According to this V3 should have much wider adjustment range and should be able to be set up a lot more comfortable or even stiffer than V2.
So if the amount of rebound adjustment clicks is the same(16 clicks),which it is, then maybe the amount 1 click changes the suspension is bigger on V3 than on V2/XA. Or maybe V3 is marked on that chart like that due to adjustable compression, that does make a difference in comfort when softened. Or this chart is just totally fake crap, made up by marketing department.

Wierd is that you said that rebound adjustment is hardly noticeable. I definetly felt changes when i turned my rebound 1 click softer. Same with compression. Thats why i started to wonder if valving adjustment is different between different models.

i do get what you are saying. Separating spring preload and ride-height would be nice and would give user more ways to dial in their setup. Many KW-s competitors do offer that.
I personally did not really care for it and was more interested in KW-s valve adjustment technology and build quality. And I believe KW doesnt make any coilover kits where ride height is separate from preload. Even Porsche 911 GT3 (991) Clubsport kit that cost 5400 eur have same type of height adjustment with spring perch. So do their custom order competition series. Even KW V5 coilovers for Lamborghini Huracan that cost almost 9 grand have height adjustment with spring perch. Clearly KW doesnt see any issues with it even on their highest end most expensive kits.

[KennyP]

https://www.e46fanatics.com/threads/...estion.912308/

As Z4 rear suspension is based on e46 rear suspension I did a search for e46 KW V3 rear springs. And this popped up. So KW has been selling springs that get compressed like that for at least 10 years now and havent even made any revisions to its products.

This from that e46 thread is interesting:

With progressive springs it can be normal for some coils to touch under static load. The "beehive" shape allows the smaller coils on the end to fit partially inside the larger center coils upon further compression

[proboner]

As an experiment I actually just bought a set of $330 CX racing coil overs for the Z4 and installed them 2 days ago. By comparison they have:

• Coil perch and strut body adjustment
• 4 coil rear springs to prevent dead coils
• Included front strut mounts (non-adjustable at this price range)
• Much more comfortable ride that stays within the shock optimal operating range regardless of ride height

I'm actually very impressed with them. Would highly recommend to anyone looking. Who knows how well they'll hold up in the long run, but right now they're a great solution.

[KennyP]

Wow 330usd? Thats like nothing. Did you take pictures? Do a review/ comparison! If you are happy with them then that is all that matters!

[proboner]

Haha I know, right!? I found one other guy who had bought a setup who said he liked them and I figured, it's only $330, I really can't lose here! I'll be doing a comparison and review soon. Currently have them on full soft and want to do a bit of driving at medium and stiff adjustment