KW suspension Spring flip thought process
 

I want to first start by saying I'm no expert in road car suspension but I do have quite a bit experience setting up Off road long travel suspension. If you've got something to add here please discuss I really want to get this car setup best as possible.


I'm concerned with the spring rate on my Frs. I think I may have figured out the problem.

My current setup is KW coil-overs setup with the Higher rate spring in the rear(out of box configuration). Compression is up +1 for the front and -2 for the rear. Rebound is Factory for front and rear.

When I go to the track unload all the stuff from the trunk remove floor mats ect.. this car gets light. So light in fact that, the rear end hikes when braking causing the rear of the car to over rotate under trail braking.
Second thing that happens is the car is a bit un compliant in the rear durring the exit on turn 13 at the Roval for instants. Also the car feels a bit unmannered in the rear. I believe this issue is I'm not using all the travel.So to combat this I turn down the compression even more this just seems to amplify the issue with braking and trail braking, in addition to making the car seem more unstable at high-speed. All these issue I believe are stemmed from a over sprung rear.

Flipping the spring will combat the front end dive, make the rear more compliant while allowing higher shock rates used to maintain control also allowing for less agressive rebound valving.( Theory only)


Unfortunately like most people on this board I use my car almost every day. So the down side of just flipping the springs around could be bad. Lets say you work in sales like I do. I usually pile in a laptop, small client file maybe some sample product and a small tool bag. this weights in at over hundred pounds. Not to mention if somebody else is in the car with me. This will quickly load up the rear of the car and make the front end light also causing the rear to become harsh and not a good ride.( This should be the side effect of flipping springs.)

I think the spring choice for this car was done so it could be used everyday not as a track car. This is the overall goal of a manufacture KW suspension is for street and track. In this case the rates suffer at the track.


Enough ranting
Just my thoughts.

I will be flipping my springs for the next event.

Gregg

We are not running the standard or the flipped configuration. I think you should adjust your rear rebound though as it sounds like maybe you are running a little too much in the rear. Is it bouncy over bumps or is it a little harsh?

What kind of tire and what size are you using?

- Andrew

aggreed with drew

think of compression as "adding hydralic spring" to an allready at the edge sprung car. rebound can be used to control the lift under braking and even "tamp down" the rear getting ready for a braking event. switching splings can flip the cars balance too pushing too.....
the KW's are so easy to adjust ride height I would drop the spring perch 3turns too
I am running a flipped setup BUT no rear sway...so it evens out (the car is HELLA low though).
search robispec for pic's

RObi

I did try running more rebound it did help the nose dive but the car got harsher through the rough stuff, also added in some more over steer on exit with power. Almost like the shock is packing up.
I'm on Weds wheels 18x8 with a offset of 45. Tires are Michelin pilot sports 245/35/18, front and rear.

You should keep your rear rebound softer (though not so soft that it's bouncy). That will stabilize the rear. Rear compression is not the issue here (for braking) though a little more front can help. I also suggest option C...changing the front springs while keeping the rears where they are.

- Andrew

Option C may work, Would you suggest the same spring for the front that are on the rear?

We are running 400/400 on our car. It works really well. We can source some springs for you if you are interested along with damper settings that will work with them.

- andrew

All things being equal, running more front spring and less rear bar will not even things out, that will dramatically bias the car towards understeer. If you still have neutral handling, it's because you changed some other variable in addition to the springs and sway bars.

Well, if I know anything about robi's cars it's that they don't understeer.

yes but almost anything you do to the car changes the balance...
going to 245 sticky street rubber changes the equation a bunch.
running the car 3" lower REALLY messes with the weight transfer
http://i240.photobucket.com/albums/f...s/IMAG0060.jpg
(in a good way)
http://i240.photobucket.com/albums/f...s/IMAG0057.jpg
we are slightly narower rear track and 1.5" wider front track than stock. Front roll center is corrected (to allow the rear to transfer weight faster) and front tierods bump steer corrected for the drop and the tubular front lower control arms.
-3.5 front camber and full bump travel front and rear.
http://i240.photobucket.com/albums/f.../rearUpper.jpg
one of the parts that helps this
the car is slightly loose under trailbraking or off throttle turn, in mid throttle gets you to neutral/slightly tight, off throttle to full throttle at apex yields barely loose corner off caught if nessisary (usually the torque loss with RPM increase does this) with a light twitch of the steering wheel we will probably soften the front spring one step to give the car a bit more front bite turn in to mid corner.

so yes You are correct
we have done more than swapped springs on installed coilovers. ;-).

I think Option C is a good one Andrew Please PM with price on front springs. Also I would think the compression can be turned down once the spring rate is upped.

After doing so more research I noticed my auto LSD is kicking in. This means one of my rear tires is coming off the ground in certain situations.

If I add spring rate to the front this should keep the rear more planted?
Or should I remove a little spring rate in the rear to help it articulate?
I also could run the front end of the car a tad bit higher than it currently is to get more weight to the rear.

ROBISPEC noticed this behaivior early on in our testing. We solved it by a comb. Of the changes we made. Lowered cofG remove rear sway added rear spring rate.

interesting post:

My take reading it was that your rear is too stiff with your setup in relation to your nose

have you tried a stiffer front sway?

does KW offer only one spring setup with this kit?

I dont think the rebound valving is your issue. What rubber are you running?

do you kno what rates your running currently?
dont go changing rates without attention to bias front to rear, and dont forget your sways affect spring rates when in corners.

The KW come out of the box at 6kg front and 7kg rear. This comes out at 340 front and 400 rear.

From my offroading experience.

We have the following happen. Front inside tire comes up= add rear sway bar.

We never have the rear lift but I also have 28" of travel so this is almost imposible.

So based on this, if the rear is coming up. Then adding more front sway control and or a stiffer spring may help.

What about this. Slightly lower rear spring rate to improve ride quality and front sway to help control weight transfer. As of right now I already have some compression valving removed from the rear to help soften it up a bit.

http://www.wopracing.com/wop_joomla/.../p2190406r.jpg


This is what I'm used to shock tuning.

if your lsd is a torsen then thats the exact opposite of what would be happening as a torsen type wont work if one of the drive tires lifts. if lift is what you really think is causing your problem (which i doubt) unbolt your rear sway bar so the wheels move more independently. that will cause the rear to jack up on turns though which is another one of your problems.

The Unsettling rear happens in turn 8-9 and turn 12 and 13. The dash blinks letting me know the rear is getting wonky. I have all the nanies turned off. I saw this little light coming on as I transition in the turns. Looks to be one more hidden nanny buried in the ECU.http://www.speedventures.com/images/SV_ACS_Roval.jpg

Does the nanny light up ONLY during trailbraking?

Even with the nannies turned off the 'hidden' VSC will send ABS pulses to the outside rear wheel under lateral slip.

You can disable all nannies via this method from 086A: http://www.ft86club.com/forums/showp...8&postcount=15

Options to permanently disable it include pulling the ABS fuse from engine bay fuse box ... not a great one since it disables front ABS too. Or installing a physical override system like this: http://www.autofactory.jp/product/to...?mode=s&seq=14

PS. Great thread, I am a bit of a suspension noob, my KWs are coming soon and looking forward to dialling them in right.

I don't think it's really a trail braking issue. On the exit of turn 8 I'm usually at about 80-85 mph this is kinda of a off camber corner to turn 9. The light will blink at me just after the kink.

I then try to settle the car because turn 9 is like second gear for me.

Just for a reference I'm not extremely fast. I'm clocking in at 2:10 at this track right now.

But I am hoping to shave down some more seconds. I heard Crawford ran a 2:02 before they went turbo.

I have some custom valved reservoir short body bilstein 7100s on my land rover, what you do off road for baja or rock crawling, and what you do on the tarmac are similar, but not quite the same. dang 28", thats alot of travel.

I'm betting your gonna benefit messing with the front to fix the back. Get rid of the OE front sway bar 1st. Try a stano, or a 20 or 22mm front adjustable set soft. get back to us. These things take time, I may have missed it, what tires are you on?

I dont think your rear rate is TOO soft, so I would go there last after everything else. You may get other advice and ideas from others. I think your finding the front end too soft, but reading it thru the rear. Can you lower compression valving in the rear,just a hair, and loosen up rebound a bit? Make small, singular adjustment, TAKE NOTES, and revisit. keep us posted, thanks

I have though about this some more. The next two steps for me are going to be increasing front springs and Front Strut tower brace/camber plates.

My hope is that by doing this, will help the car from nose diving, and should keep the rear more planted during braking.
Second, the Stiffer spring's should help keep the rear more planted during left to right transitions.( If I need more I will add a sway bar to the front.)

The Strut tower Bar should just improve the overall feel helping maintain control through reduced chasis flex. I dont want to go to stiff because I think the chassis will wear out quicker if everything is super stiff especially If I dont have a cage.

I will add Go pro's to my suspension components to help tune.

Food for thought.

Gregg

Not quite THAT fast. http://www.mylaps.com/results/showrun.jsp?id=2392393

They also ran a 1:59 the one session the car was run with the turbo, although I don't believe it's indicative of the car's true potential, as it was the first time on track after it was boosted. http://www.speedventures.com/results...id=-2146754468

I don't know what tires they ran on those days.

Dan Gardner ran a 2:02 that weekend on I believe BFG R1.


How bad was your trail braking issue? I've been fighting that issue as well to a degree...

Just got back from a 280 mile drive. I had to meet a contractor out in El centro. This drive is great I had quite a few 90 mph to 30 mile corners come up. I spent a good amount of time really analyzing whats happening to the car. The rear just feels light in the braking zones. On the street this really isn't much of a problem I dont brake that late and I drive a lot more conservative on the road.


On the track when looking for that last possible inch before turn in. Is when the car gets the most unsettled. I will order springs keep you guys posted on my thoughts with this.

Have we talked about your alignment?

- drew

no talk of alignment yet. I'm a slight toe out. I think .12 degrees out on the front with zero on the rear.

O rear camber?

- drew

Camber is 1.5 for the front 1.7 rear

Just to bring this up to speed this weekend I flipped the the rear spring to the front. I also added some ground control upper camber plates. More on this install process. I will also be giving a full review on the difference. On and off the track.


Gregg

Just wanted to update this thread for people who would be interested in flipping their KW springs.






Perception:

Ride quality is very good. Seems smoother.
Steering response is increased( do to the higher spring rates)
Articulation has increased, the rear of the car stay's on the ground entering steep driveways, before would pull a tire.




Tonight I took one of my favorite roads very twisty tight with some good bumps mid corner. I notice the rear of the car while planted does sway more now with the 1kg lower rate. I'm currently on the out of the box setting for the compression. I will try upping the compression to help combat the chassis sway.

The car now feels much less lively very planted and "safer"/easier to drive. It's really hard to tell how the car is going to react on a track other than to just get out there and try it. I will mention that I do plan on ordering some 7kg springs for the rear, and have those ready to go if the car performs poorly on the track.

The oversteer tendency has defiantly been subsided I'm just not sure that is a good thing or not yet.


Gregg