Coilovers: Illumina's vs. Koni's, spring rates, please help!

[johnc]

It's mentioned alot here that stiffer rear spring rates than fronts is the way to go.

 

That's one way of tuning the S30 chassis. Here's my opinion on where that setup came from and why:

 

The 240Z, even heavily modified, is a car that does not turn in well compared to other race cars of its day (RX2/3, 911, 914, etc.). Add to that the fact that most CP racers of the 1970s (and most ITS racers of today) ran a welded rear diff which induces a lot of understeer on trailing throttle (corner entry) and you have a car that doesn't want to rotate into a corner.

 

To counter that a lot of the CP and ITS racers ran (run) more roll stiffness in the rear to loosen up the back. That additonal roll stiffness combined with a little bit of trail braking gets the car to turn in reasonably well and keeps it neutral mid corner (keeps the understeer away). With a welded diff corner exit speed is not affected by inside rear wheel lift or a little bit of slide as long as the driver can balance the car with the throttle.

 

Its a setup that's worked well for decades given the technology available during the 1970s, 1980s, and early 1990s. It still works well today on tighter, bumpier tracks

 

With a greater avialablity of clutch pack, Torsen, and Quiafe LSDs and more sopisticated shocks, some racers started experimenting with reducing rear roll siffness (smaller rear bar and springs, bigger front bar and springs). This can allow earlier throttle application in a corner and faster corner exit speeds. It took some devleopment time for those setups to start working but by the early 2000 it became the fast tune for ITS 240Zs. Chet Whittle proved that with a couple wins at the ARRC running a clutch pack LSD, Shock Tec double adjustable shocks, and a 200hp Sunbelt L24.

[evildky]

my understanding is the national level FP guys are runnign 400 lb all the way around, as mentioned I run stiffer front and lighter rears, I found that the stiff rear had a tendancy to oversteer....A LOT! I also found a lack of straight line traction, granted I'm putting down a lot more power than the FP guys and have no trouble getting the rear to rotate and brake traction at will, also my turbo setup is gonna weigh a bit more than their carbed setups and my chassis has not had any stiffeneing at all and the 440's make the frotn feel really planted

[EMWHYR0HEN]

Iv'e been running my 240Z on 300lb fronts and 350lb rears with Koni adj. for quite a while now. Half the time I ran with the stock sway bar up front and no rear. No LSD, 195/14's. Some of my observations:

 

My turn in and corner entry speed was fast, almost too fast. Sometimes I had trouble with clipping the apex early.

 

Corner exit speeds were slow. I wasn't able to get on the gas early without some oversteer.

 

Putting power down (even though I didnt have much of it) was tricky.

 

Adding 1'' sway up front and 3/4 in the rear made the car turn in even quicker and exit even slower.

[tube80z]

my understanding is the national level FP guys are runnign 400 lb all the way around, as mentioned I run stiffer front and lighter rears, I found that the stiff rear had a tendancy to oversteer....A LOT! I also found a lack of straight line traction, granted I'm putting down a lot more power than the FP guys and have no trouble getting the rear to rotate and brake traction at will, also my turbo setup is gonna weigh a bit more than their carbed setups and my chassis has not had any stiffeneing at all and the 440's make the frotn feel really planted

 

You have something else wrong with your car. We run stiffer than what you're talking about and have no issues with straight line traction or oversteer. And this is with cars with big torque too.

 

Cary

[johnc]

No LSD, 195/14's.

 

I see something wrong here...

[EMWHYR0HEN]

I see something wrong here...

 

I know. It was my steet car then. Pm sent about welded diffs.

[evildky]

You have something else wrong with your car. We run stiffer than what you're talking about and have no issues with straight line traction or oversteer. And this is with cars with big torque too.

 

Cary

 

please do enlighten us to what rates you are running? time holt pops in occasionally maybe he can clarfy his setup, as for me, I do run MSA bars frotn and rear, I am pputting down over 300 lbft of torque I believe thats a bit more than the FP guys, I also run megasquirt with a very agressive spark curve which makes the throttle more of an on off switch, and i am running V710's on 17x12's so your cantilevered slicks on smaller wheels might be a bit mroe forgiving

[tube80z]

please do enlighten us to what rates you are running? time holt pops in occasionally maybe he can clarfy his setup, as for me, I do run MSA bars frotn and rear, I am pputting down over 300 lbft of torque I believe thats a bit more than the FP guys, I also run megasquirt with a very agressive spark curve which makes the throttle more of an on off switch, and i am running V710's on 17x12's so your cantilevered slicks on smaller wheels might be a bit mroe forgiving

 

A friend had a car similar to yours but LS-1 powered. It was probably 350 WHP and similar torque. 17x12 kumhos in back with 425 front spring, 400 rear, and similar bars. Very neutral and it's strength was how it could squirt out of corners. The one issue this car had was it worked the rear tires pretty hard and this was from the rear roll center being too high in my opinion. I think if that was fixed it would have been much better.

 

The FP and XP cars we running all are currently at least 550 all round or higher. We're using FA tires rather than cantilevers. We have two cars currently running V8s with over 300 WTQ and they put the power down in corners and have excellent straight line traction. There are others on this forum with big HP/TQ and similar setups (Clifton comes to mind).

 

It seems from an earlier thread you mentioned you had 250 springs in the back. When I first got my car it was setup like this all the stiffness in the front and very soft in the back (PO stated what you describe). The car was very adept at three wheeling on corners. Running a more balanced setup fixed this and the car was much faster.

 

If you know you're corner weights try springs that give a wheel rate of about 0.8 times the corner weight. That seems a good rule of thumb for the street radials. On slicks we're trying to be closer to 1 and I hope to experiment with higher rates this summer.

 

Hope this helps, I'm happy to tell you all the settings on our cars.

 

Cary

[evildky]

I'm not 3 wheeling, but I do run a rear sway bar, I tried the 440's all around and the back was like skating on ice and I could not give full throttle on a straight, not corner exit, I mean a fully settled straight! I have no doubt taht you have other race cars makign as much or more power than I my point was that the FP guys at nationals are very fast and they are in the 250 hp and torque range and also run the softer tires on smaller wheels

[TONY C]

My experiances Not Gospel!

225 front 250 rear. Tokico Ilumina. Bouncy. Poor ride quality. 2 years of hard street driving they were all leaking. 6 months later I am still waiting for them to make them good.

Tokico= Total Crap!

Same springs. Koni Special "D" inserts. Excellent traction. Never knew the car could drive soo good and corner even better. Firm but not harsh.

My G-tech says I am putting 290hp to the wheels.

Koni for the win!

[1 tuff z]

Wanted to post my specs & ask advice. Here is my driving "perception"; turn in is a bit slower than I'd like and car understeers unless I trail brake for nearly each corner. Car is street driven and sees duty 4x per year at Watkins Glen. My concerns are; car does not feel as buttoned down or solid as I'd like [i don't feel confident going as fast through the esses as I do in other cars I've driven, my favorite is a friends 90 300zx n/a]. Also, my tires are 'rounding' on outer portion of tread-front tires. Thanks, in advance, for any help/guidance!

Current setup;

-Weight [1/2 tank gas] 2769, total wt 2944; front:1451, rear:1493 [including175# driver-me],

-Corner wt w/175# driver; 754 LF, 747 LR, 703 RF,740 RR, f/r weight distribution 49.3/50.7, cross weights 50.7% lf/rr, 49.3 rf/lr

-Ride height 6 3/8†front [measured at centerline,trailing portion of t/c link], 5†rear [measured at seatbelt pocket]

-Front; caster +4.0 both, camber -1.6 both, toe in 1/16 total

-Rear; camber -1.7L, -1.7R, toe in 1/8 each side

-Suspension; GC coilovers w/front camberplates, ZF racing lower front suspension components, Techno Toy Tuning rear control arms, Eibach 225 lb springs front, Eibach 250 lb springs rear, Tokico illumina struts [new from Beta M'sports 4/2010], 1†front anti-roll bar, No rear anti-roll bar

· -Tires-Toyo T1-S 245/35/17 on Compomotive 17â€x8.5â€wheels

 

 

 

 

 

 

 

 

 

 

 

 

 

[zredbaron]

1†front anti-roll bar, No rear anti-roll bar

 

I'm not enough of an expert on the other stuff to advise, but I can speak to the ARBs. I raced a full season with 1" up front and nothing in the rear. This allowed me to put power down earlier and more aggressively, but at the expense of turn-in, which the S30 already struggles with as it is.

 

My S30 is about 2300 lbs with fuel and driver, and I still could not get it to turn in. Absolute pig. I had to either slow down waaayyy too much, or tap the brakes while I was still on neutral gas pedal to get it to turn in. It was fastest time-wise (around cones at low speeds) if I allowed the rear to slip slightly and let the torque contribute to the turn.

 

I've since gone fully adjustable front and rear hoping to remedy my setup; the driver shouldn't have to be the fix to a poor suspension setup! Can't report on it yet, as the project isn't done and I haven't raced it yet, but I believe it's a step in the right direction...

[johnc]

GC coilovers w/front camberplates

 

Get these...

[Mikelly]

David, As I mentioned in my email offline, I'm running 400# rear springs, 500# front springs, no rear bar, 1 inch front bar, ZF Racing lower bits, GC camber plates up front, AZcar chromoly arms in the rear with AZcar rear upper plates. The strut inserts are Koni 8610s.

 

The car is surprisingly NOT bone jarring, even with the extensive cage and subframes. When I was driving around Watkins Glen with a passenger in the car, we both noted that the ride was exceptionally compliant.

 

Running 2.5- front camber, and 4+ caster, with 2.2- camber in the rear. I'll find out within the next month or so how the car performs!

 

Mike

Edited October 3, 2011 by Mikelly

[1 tuff z]

Mike, thanks for the info. I'd also like to know type & size of tire and your feedback on the handling of your z from the next event.

 

David

[Mikelly]

David, I'll be running Hoosier R6s in 245 (front) and 275 (rear) sizes on my 9.5 inch TSWs. I plan to upgrade to CCWs with a 275 and 295 over the winter, along with fuel injection.

 

Mike

Edited October 3, 2011 by Mikelly

[RebekahsZ]

1tuffz-follow Mr. Coffey's advice - you need more front camber. That is what the pushing and rounding of your tires is telling you. You go to the track more often than I do, but I solved the problems you describe really easy over one weekend with camber plates that allowed 3-degrees of neg camber. Totally improved cornering. Talk to John C about his bolt in camber plates. I have EMIs in the front (there seems to be a problem getting these) and I have DPs in the rear, both bought thru BetaMotorsports.

[Gavin]

Just reporting my experience.

 

I sectioned my 78 280z struts with the 8610 (rebound adjustable) in front and 8611 (two-way adjust) in the rear with 400 lb springs all around. I did this with the intent of generally trailering the car. To my surprise, with the shocks on full soft, it feels better than it had on the street. Although its feels undoubtedly more stiff than my previous Tokico blues and Eibach sport springs, I suppose I have to credit the quality of the shocks for the superb ride. I have done 5 autox events at a local airfield (60-90 second runs, 60-90 mph top) since the install and the car does not remotely resemble what it used to be. With just a 1-2 clicks on the shocks and old 225 RE070 140 tread wear tires, its completely easy to drive, completely neutral, stiff bit with great weight transfer, way beyond my expectations. I can now let a stranger drive the car without expecting them to hit 1/4 of the cones and spin twice.

Edited October 25, 2011 by Gavin

[johnc]

To my surprise, with the shocks on full soft, it feels better than it had on the street. Although its feels undoubtedly more stiff than my previous Tokico blues and Eibach sport springs, I suppose I have to credit the quality of the shocks for the superb ride

.

 

Exactly! Most street performance shocks have too much compresison damping. Shock manufacturers up the compression damping to make up for soft springs and give street drivers that "...hard ride..." that people confuse with good handling. I had a passenger describe the ride in my racing 240Z with 375 lb in. springs and Penske 8760 shocks as "...flying around the race track on little car feet..."