What Spring Rates Are You Running?

[seank]

Originally Posted by TSM330i

Anyone know what the spring rates should be for a full-blown race car? No street driving at all.
More than likely, going to run AST4200 or 5200.
This would be for a non-M.
Thanks

That would depend on racing weight and how smooth the tracks are where you live. Some also prefer a stiffer or softer set-up.

I hope someone chimes in. There aren't many z4 race cars.

[Beedub]

e85 //M
kw clubsport, including Kw uniball camber plates
400lb linear fronts progressive rear spring with end rate of 700lbs (according to kw)
stock sway bars
(additions)
turner rtab limiters
front strut brace
poly bushed RE reinforced top mounts (rear)
Camber shims installed, camber set to -2.7

settings are 6 clicks front rear 12 clicks on rebound, bump is 0.75 on each axle.

[TSM330i]

Originally Posted by seank

That would depend on racing weight and how smooth the tracks are where you live. Some also prefer a stiffer or softer set-up.

I hope someone chimes in. There aren't many z4 race cars.

Car weight with driver would be 2,800lbs. and we definitely prefer a stiffer set-up vs. a softer one. Most of the tracks are pretty smooth. We are currently running a 335 that we want to either retire from competition or use less often. We run a pretty stiff setup on that and it works very well. The car is a pig at 3,300lbs, gutted, but with the fuel cell and full cage, it adds so much weight back in. The Z4 is light from the start so it's not too hard to get it down below the 2800lb mark.
We'd also rent out the Z4 for driver schools, teams with licensed drivers that want to run sprint races or 12 hour races.

We may have to contact TC Kline. I think they raced a Z4 in the past.

[seank]

I think they raced a Z4 in the past.

They won 2 national championships. TC told me that they ran 400# springs front and rear (not a typo), with no rear sway bar most of the time. Larger sway in the front.

He likes a very soft set-up. Too soft for me.

[jmillet]

2007 E86 Z4MC S54
TCK DA coil overs with 500#F and 600#R. TCK camber/caster plates.
Primarily track but does see some limited street use.
Instruct at BMW CCA and PCA driving school events; about 12 track events a year.
Running stock sway bars.
For track use run Toyo R-888 tires and PF-06 brake pads.

Originally Posted by seank

jmillet

Nice pic, but do you have any figures for us?

[S2000]

1) Chassis and motor - 2007 Z4M Coupe, stock motor.
2) Which coilover brand? - KW Clubsport
3) What size springs and rates front/rear? - 400lb front/ progressive rear
4) Is your car track only or street & track? - street and track
5) What kind of events and how many events per year? (ie, auto-x, DE, TT, club racing) DE - 8 events/year
6) Are you using aftermarket swaybars? No

The rest of suspension is stock.
Getting -3.5 front camber and -2.5 rear camber.
Experimented with R888 245/275, NT01 245/275, Hankook C51 245 front, Hoosier 255/40 rear, Hoosier 255/35 front, 255/40 rear, NT01 275 front with 12.5mm spacer (increased ride height by .25" to reduce rubbing), 275 rear.

Would love to ride on cars with AST 5100 or Nitron R1 to compare with KW Clubsport handling.

[S2000]

Recent 2013 change:

1) Chassis and motor - 2007 Z4M Coupe, stock motor.
2) Which coilover brand? - AST4150
3) What size springs and rates front/rear? - 5" 616lb/5" 728lb
4) Is your car track only or street & track? - street and track
5) What kind of events and how many events per year? (ie, auto-x, DE, TT, club racing) DE - 16 track days /year
6) Are you using aftermarket swaybars? No

Getting -4.0 front camber with turnermotorsport bolt and -2.1 rear camber.
Running 275/35/18 square on 18x10" ET25 wheels.

[donoman]

I'm running 375 lb/in front and 440 lb/in rear. My ass is getting air over big bumps... this can't be good, right?

Ground Control Coilover Kit with GC Street Camber plates

[seank]

Originally Posted by donoman

I'm running 375 lb/in front and 440 lb/in rear. My ass is getting air over big bumps... this can't be good, right?

Ground Control Coilover Kit with GC Street Camber plates

That has to do with the valve adjustment, not your spring rates. It shouldn't be an issue except for ride quality and traction.

[donoman]

Called GC... They told me to adjust the Koni's very little. Like 1/12th of a rotation per time. I was trying to tune the damping by going +1 turn or -1 turn... way too much. Overshooting every time. Just adjusted during lunch... car is driving much nicer now.

[AriuSen]

sorry...reviving this thread.....hose who shared your spring height.....are these with helper spring??
If I want to use a helper spring on front, I should go with 5.5" or 6"?
and without helper spring a 6"?

[JJZ4MR]

Great thread, trying to gain some info on spring rates stock VS options. Have a local in Tampa who has BC Coilovers up for sale on here in Classifieds. I'm not really ready to install. They sell new for $1000 shipped, his have one year of use use 5K miles/like new condition he wants $800, figuring if I could get him down to $500 I'd squirrel them away for when I'm ready.

Here's my nube question : Spring rates are 6K and 8K. Are these additional to my stock springs ? Are the stock springs taken off as well as shocks when going with coilovers ? I looked at a coilover DIY instructional and was still unsure ? What are the stock spring rates of my 2006 Z4MR ? I've just started AX ( 2 completed and love it ) and I plan on moving up to HPDE in the near future ( Sebring )

[AriuSen]

Originally Posted by JJZ4MR

Great thread, trying to gain some info on spring rates stock VS options. Have a local in Tampa who has BC Coilovers up for sale on here in Classifieds. I'm not really ready to install. They sell new for $1000 shipped, his have one year of use use 5K miles/like new condition he wants $800, figuring if I could get him down to $500 I'd squirrel them away for when I'm ready.

Here's my nube question : Spring rates are 6K and 8K. Are these additional to my stock springs ? Are the stock springs taken off as well as shocks when going with coilovers ? I looked at a coilover DIY instructional and was still unsure ? What are the stock spring rates of my 2006 Z4MR ? I've just started AX ( 2 completed and love it ) and I plan on moving up to HPDE in the near future ( Sebring )

if you install coilover, you dont use stock springs anymore. they are too wide for coilovers.

[JJZ4MR]

I'm never afraid to ask a question. I feel that my suspension in general feels soft. As I make wide circular turns at the end of the runway for the AX, feels like the inside edge of the car comes way up.

[dre99gsx]

1) 3.0si coupe, 2jz (about 100lb more weight on front than S54)
2) KW Clubsport, all linear springs
3) front: 6.4" 504# + helper spring, rear: 4.7" 672# (these are BC springs)
4) track
5) DE events, 20 days per year
6) H&R front sway middle setting, non-sport smaller stock rear (18mm) - sport comes with 19mm, (sway mounting reinforced in front)

The car is "loose", and I exhibit controlled corner entry and mid corner rear slip, too much for my comfort. I trail brake a lot, and it could be the cause, but mid-corner has me more worried. Car also has a bit more front squat that I would like during braking.

JRZ's catalog has these rates:
level1: 450/550 (fr/rear)
level2: 650/750
level3: 800/900

Notice how they are 100 lb diff front to rear.

Stock Clubsport came with 400/Prog (I read up to 700 max in rear)

And, I'm running: 504/672

I want to raise the front spring rate a bit. Any suggestions? I purchased 600lb springs, but am afraid that may be too much. I have an option of 560lb springs. Does anyone know how sensitive our platform is to rate changes? Would hate to hit the track and now get massive understeer - swapping out springs isn't that easy of a task.

[F360C]

Up front I have run everything from 525lbs up to the 750lbs. I run one really bumpy track often (like NJ roads bumpy) and I dont find the 750lbs front too stiff. My current set up is 750/850. I think the biggest change I made was lowering the gap in rate from front to rear. With all my previous springs I have run a 125-150lbs gap from front to rear. With lower the gap front to rear I found I eliminated a lot of under steer.

edit.. forgot to mention i am not running a rear sway bar any more but have a bigger GC bar in the front running pretty close to full soft.

[Vanne]

Interesting.. currently converting my car to full race. The suspension has me guessing, and I hate guess work.
Going to stay with front Clubsports minus helper springs. Rear is to be completely custom rebuilt. With the rear frame notched and custom sub frame mounts to allow the non stock ride height suspension travel. Rear suspension components/arms also completely non stock. Car is estimating to sit about 1.5 inch above the ground. Front steering /suspension arms also completely non stock to allow for correct geometry with the low ride height.
Hopefully testing end Jan, prob Feb..

[Michael9218]

Curious if you’ve thought about how you’re going to get this car to the track. At 2 3/4” chassis height, I need 12’ ramps to load the car on my trailer.

[Vanne]

Yeah. I have a little Micheal, front nose and splitter will be quick disconnect, and will be off the car for getting to and from the track. Not exactly sure how it's all going to pan out, but yeah I am a little worried. Difficult enought getting a jack under my car the way it is now, let alone when it's sitting an inch and a half off the ground..
Wooden slight slope ramps for each wheel is what I'll probably fab up out of wood.

[ANILE8]

1) Z4M Coupe
2) Nitron NTR-3 Coilovers
3) Front 7"/400# and Rear 5"/500# springs (with helper springs and R/E weighted Jacks)
4) Street driven these days
5)
6) Stock swaybars