Need help eliminating oversteer
 

I am running a full race 370z and I have been struggling with oversteer. Now, I don't mind a car that oversteers, but I can't stand dancing the car through turns and having to wait to go to power after the apex because the *** wants to swap ends with the front.

The car is lowered and running on JRZ double adjustable coil over's. Spring rates are 1K up front and 800 rear. The bar is disconnected in the back to try to get some bite, but it's still only a partial fix. We have experimented with dampening and now I am pulling the shocks to soften the springs in the rear, but I just don't think I am going to get a marked improvement without altering the geometry in the back.

Is there anybody that has ANY feedback on the WiseFab rear suspension upgrade? Is there a significant improvement to be had by using their geometry?

Any help would be appreciated. Feel free to ask questions if you need.

Curious.....Tire compound and size? Aero? Current alignment reading?

Yep need a lot more information on your setup before we can begin to answer your questions.

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I have all the data in my binder in the transporter and the car is out of state. I will have to get back to you when I get the car back this weekend.

Thanks for the quick responses.

There's some info in here on this same topic.
http://www.the370z.com/brakes-suspen...ndersteer.html

Ok, here is more information:

Front wheels:
18x9.5 Enkei NT03+M / 275/30 Hoosier R7

Rear wheels:
18x10.5 Enkei NT03+M / 295/30 Hoosier R7

Left Front
-2.9 Camber
5 Caster
.09 Toe

Front total toe
.19

Steer ahead
0.00

Right Front
-2.3 Camber
5 Caster
.10 Toe

Left Rear
-2 Camber
.22 Toe

Right Rear
-2 Camber
.21 Toe

Rear Total Toe
0.44

Rear thrust angle
0.01

Chassis:
TC Designs custom cage with reinforcement to firewall
JRZ RS-Pro 2-way adjustable dampers with Hyperco springs 1000 / 800
SPL rear camber arms
SPL rear toe links
SPL rear knuckle monoball bushings
SPC front camber arms
Hotchkis sway bars

Drivetrain:
OS Giken 1.5 way differential with 3.54 gears
Short shift
Custom tilton/ setrab diff cooler with toggle switch
Diff Pump and cooler

Brakes
Stoptech Trophy motorsports brakes with slotted rotors. 6 piston front, dual piston rear.
Tevis stand alone motorsports ABS system with Tilton adjustable bias valve

Engine
Stillen gen 3 intake
Tuned for 93 octane 354 WHP/ 305 WTQ on Pellegrini Performance dynojet
AE Performance oil cooler
Custom 4 -> 1 SS Exhaust
Long tube headers from Fast Intentions

Fuel:
ATL 32 Gallon FIA certified Fuel Cell
Moroso Fuel Pump
Moroso fuse panel and switches

Interior
Sparco 330mm flat bottom steering wheel with quick release
Steering wheel mounted controls (Radio, Brights, Cool Shirt, PTP, Limiter)
AFFF Fire system
Custom carbon switch panel
Custom dead pedal
Battery relocated to trunk area

Aero:
Aeromotions carbon wing
Lowered front end and splitter
Front underpan
Midsection underpan
Carbon rear deck
Lexan windows
Carbon lowered side skirts
Composite fenders with exhaust ducting
3" carbon front brake cooling intakes and ducts

https://www.instagram.com/p/BmCOCkrB...y=too_cool_dad

I need to see some pictures of your car she sounds bad *** and you got all the good stuff.

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I'm not sure this will work or not:

https://www.instagram.com/p/BmCOASBF...y=too_cool_dad

https://www.instagram.com/p/BmCOCkrB...y=too_cool_dad

You may want to get her corner balanced since you gone full race car before you start making adjustments. That will help with getting your spring rates and ride height to a place you can start to work from.

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Did that.

Yep the link does not work... I sent you a follow request!

Ok cool it looks like your camber is .5 degrees apart on the front. Is that a typo? Also you could add some more front camber -3.3 and increase your caster to 6 or more. Your rear seams spot on.

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Wow standalone ABS. You weren't kidding when you said a full race car.

Could you describe the oversteer? Was it entry, mid corner, exit, or left to right transition?

When you've gone into thinking changing rear suspension geometry, I am sure you have already tried the usual suspects, like toe, downforce, rebound and compression settings, brake bias....It'll be great if you can share the different adjustments you've made and your conclusions on them.

And the SPC front camber arms...typo?

The bite at the front is good, the oversteer is the issue. I am researching suspension alternatives for the rear that can improve the grip with new geometric angles since the car is lowered.

Too add to that question. Is it tail happy all the time? Or at different corner speeds? What's your tire temps across the tires. What's your fuel level when it happens? How many heat cycles on the tires?

:iagree: Really.

Another question. How did you get 354HP with a Stillen G3 and FI LTH's? What else was done?

Copy that, my setup is somewhat close to yours. I have pretty much the same suspension up grades except for one way coilovers 14k front and 11k rear. I run no bar in the back as well. I run square but not on slicks, nt01's 315 30. I am lowered as well and have just a slight oversteer.

I mentioned this in another thread but in talking with a Nissan employee while looking at some Nissan race cars in their heritage collection he said you might want add some weight over your axles. He went on to say that every z back in the day had added weight in the rear. He the showed me a few cars with post over the rear tire well were they added the weight help the car with traction.


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I certainly don't want to add weight to the car. It's hard enough to be competitive against E46's. The car does perform differently on a full tank of fuel. Since we put the large cell into the car for endurance events, but you can't count on that because it is a dynamic change to the car. We custom built the cell to replace the stock tank and keep the fuel as low as possible.

Did I read correctly that you are running 315's square? WOW, that's a LOT of tire. The front bite is so good on the car, that we can't induce any slip on the 275 fronts, so the added weight just wasn't worth it to us. I notice that you also have VERY heavy springs. Did you do that to prevent squat and loss of camber through the suspension travel?

It's a bone stock motor (has to be for racing). There wasn't much magic done here, the exhaust has a lot to do with the performance. The car IS ear shattering at speed as a result, but I don't care who suffers as long as I have the power. When we have to muffle down for certain events, there IS a loss in power (Thank you Lime Rock Park). I have the car tuned at Vinny Ten Racing, and if you are running a VQR motor, I would strongly recommend them!

The car is tame in the straight braking zone and becomes slightly lose as you trail into the turn. You have to be careful not to carry too much speed or the back will start to wash out and this will destroy your turn. It's predictable for rotation at the apex which is helpful, but I would rather have the added grip. Once through the apex, the car doesn't let you go back to power without the back pushing out. You have to very gently add power through the track out without getting too excided, but as you get closer to a straight wheel, you can go back to power. I can hear the E46's get back to full power ahead of me. The crappy part is that I have the power on the straight, so I can reel them back in, but lose the distance again at the next corner.

The WORST thing about this is that we rent seats out for endurance racing and we use the car for instruction and when we put somebody in the seat with slightly less experience, it becomes a dangerous situation.

I think this is your car. Nice mods.

http://www.zcarblog.com/for-sale-1/2...-370z-race-car

What are your spring rates in? Pounds per square inch or Kilograms per mm.
Most folks on this board use Kg/mm. The hard core autocrossers and racers use Lb/in.
It's sounds like you have the suspension adjusted all whacky causing the oversteering issue.

I totally understand not wanting to add anymore weight being NA. When I have suggested this to others whether road or drag goers, the answer is the as yours...the car does hook better with a full tank of gas but is slower.

I run two sets of wheels one that is 18x11 +18 square with 315 30 tires and 18x10.5 +30 square with 295 30 on them. I am boosted so weight balance and grip is what I continue to push for. The nt01 in 315 are actually really good up front. Turn is good with an equally good initial bit and grip consistent through the turn in and exit. The r888 295 are good for about a session and half before they become greasy and do not hold their grip.

I just had my coilovers serviced and upgraded by Fortune Auto and they recommended that for my car setup to go with the heavy springs all around. I think you logic is spot for the reason why some companies recommend heavy spring rates. Not all do and some have more spring to rear than front. I believe HKS is that way.

Thank you for providing detail on what you are experiencing. It is obvious you have a lot more track experience than I do and I hopefully we can find some solution to what you are describing. Although I might not be driving as aggressively as you are I know exactly what you are talking about when accelerating out of low to medium speed turns. I have thought it was and still maybe to a degree my inexperience and driving technique along with boost (torque) coming on strong and early. That said, if I must go to second gear I have to really be light on the throttle or allow the car to totally rotate beyond the apex to apply throttle many times I simply stay in third gear for risk of loosing to much time or spinning out. It is definitely annoying to run away from most in my run group only to be caught in the corners because of poor exit speed. I am not a fan of short twisty tracks because of this.

You said you were researching some geometric suspension alternatives, care to share what you have found so far? I know some of the folks that are doing the quarter mile and half mile thing are making strides in this area and it is very much on the down low as records continue to be broken in the straight line game.

Because of the camber curve being what it is on the Z. Steep. Sometimes I wonder if we are running too much in the rear.

I reduced mine back to -1.8 from -2.0 but I got to sort things out again as my whole rear setup has changed again. I now have true coilovers and higher spring rate and the car sits lower. I have not been to the track since I changed things up, but she felt a lot more balanced on the dragon. I also softened the damping in the rear quite a bit. Out of 24 clicks I went with 10 in the rear and 12 in the front. Before the change on a slightly softer rear spring, 11k and a less aggressive damper, it was set at 18 clicks.

Mr. Kroll, are you on true coilovers?

I believe JRZ only has true type for the Z34

I thought so, but didn't want to assume. Thanks....

That’s her!

The problem is that with a lowered car, the camber is set at a point in the suspension travel that is typically reserved for a “compressed” state. This leads to rapid and noticeable change in kenimatics when compressed further. This keads many people to over “spring” the car to prevent further geometric progression and loss of grip. This car is NOT designed to be lowered to this degree. I’m thinking of raising the ride height, installing spacers (or even the WiseFab kit). To change the kinematics to favor a bit of squat and body roll.

Yes. JRZ RS Pro 2 way

I didn't see mention if you had a SPL rear sub-frame bushing kit. If you do. you can add and subtract spacers to change some handling characteristics.

From the list on SPL parts on that are list on the add that the car was posted for sale you are still missing some really good an necessary suspension parts as Rusty is eluding too. I and Rusty have all of their front and rear suspension parts installed. I am really interested to see how the Z behaves on the true coilovers and running on stiffer springs but not as much dampening.

I don't know if Eagle is lurking around as he has his car dialed in and might be able to provide some input. I do know BILSTEIN coilovers and has SPL suspension products.

I am surprised BGTV8 hasn't chimed in yet.

Been busy .............. still traveling 2000km to work each week(by air - not driving) and trying to keep SWMBO happy leaves me with almost zero time.

In terms of rear suspension setup, I have deliberately used lower diameter tyres to drop the CoG rather than over-lowering on the spring perches which as several have surmised leads to excessive camber gain in the rear in bump and camber-reversal in pitch under braking being the cause of rear instability.

Over springing the car will kill rear grip - which some folks counter with a really fat tyre (needed perhaps for FI cars but not IMHO a NA car). I reckon that a 275 wide tyre in 35 profile on square setup to be ideal for me although others clearly prefer a bigger tyre.

I am happy with the balance on 265/35R18 (Yoki A050) or 275/35R18 (NT01) and will be running either Dunlop 280/650R18 slick or perhaps a Pirelli 285/645R18 and therefore following the pattern of lower diameter tyre to drop the car rather than lowering it on the spring which stuffs-up suspension angles and compromises rear camber control in bump as well as getting some weird angles in droop as the car pitches under braking which can affect your ability to rotate the car as you come off the brakes. Somewhere I have the SusProg details of the Z34 rear suspension and I was surprised at some of the changes in droop - which is something to remember - camber gain in bump is one factor to look at, but so is camber and toe change under droop as the car pitches under heavy braking. Remember that the rate of pitch is affected by rebound in the rear shocks and bump in the fronts and the recovery is governed by rebound at the front and bump at the rear so a hard turn-in can be affected by rear toe/camber recovery as you come out of the brake, depending on these settings

I have a 3.9:1 diff with Quaife LSD and a 4.08:1 with KAAZ LSD for fast and slow circuits respectively.

I go back to the settings that Doran Racing used in Grand Am and took my initial lead from them.

I've limited my drop on the springs and added 5mm of rake by dropping only 15mm at the rear and 20mm at the rear as my absolute lowering limit, which still does get played with from time to time.

I have just measured from bottom edge of the rim to the under-edge of the wheel arch which are 610mm all round on my DD wheels (245/45R18 fronts and 275/40R18 rears) - these tyres are Falken FK453 at 677.7mm dia front and 677.2mm rear. My track Enkei's RUN 275/35R18 NT01 at present and these are 650mm tall - so tyre height accounts for around 13mm CoG overall drop. I run KWv3 shocks (front rate is 425lb/in and rear is 450lb/in) but have Penske double adjustables to go into the car when I take it off the road. Spring rates will rise to ~550 front and ~650+ at the rear on proper coil-overs as a starting point but there will be a lot of testing to get it right.

I am running quite a soft setup (Whiteline front bar, full stiff and Whiteline rear bar fitted but currently disconnected - sometimes I run it on softest setting if I need to shift balance to the front depending on track and/or track grip).

I have the yaw-sensor DIY installed as the standard electronics are dangerous on the track - even with VDC off, there are sufficient electronic nannies left to cause problems which I reckon is dangerous.

I also have the SPL FUCA installed and the balance of SPL bits for both front and rear suspension/subframe but not yet installed as the car is still my sometime/weekend drive (I have a Ford Ranger ute as my actual DD) and not a dedicated track car.

As soon as the car comes off the road (it has 160K kms on it now) it will get the complete SPL suspension upgrade and Penske shocks installed as well as 4-litre forged engine, Motec M150 and QBE69G gearbox which is when suspension tuning really starts. I also have AP brakes to go onto it and if I can persuade one of my suppliers to part with his old-spec Bosch MotorSport ABS - I'll have that as well. The Motec can also support launch and tunable traction control but that will be a bit down the track I think

Do you still have the Doran Racing specs?

I have been thinking of reaching out to Rearden to see if they might be willing to share some information as well. They have been kicking butt in the PWC.

Andrew from Tachterion Driver Development | Making you faster one lap at a time! is an excellent driver who could defiantly find the culprit here. Your car is very different from what most people have and at least for me would be hard to diagnose. The only thing I notice, your spring rate is fairly "standard" and you should be looking at changing the rates to less in the back and maybe even more in the front but I'm not the best at this by far. Mine (full interior) is 1000/450.


http://www.the370z.com/members/2011-...03-14-2018.jpg
I wish I had my current settings handy, I almost have it right but the rear needs more work.

I am not that expert as most people here, but I will give my 0.02$

A lot of informative replies, I didn't read all of it, but I have nearly the same issue right now, and it appeared when my friend drove it, he couldn't complete an AutoX run in it as he spinned all the time :icon14: mainly due to his early throttle input. I didn't have this problem before, what have changed from my last setup which was very balanced with slight oversteer.

Tires: from RE71R 275/35-285/35 combo to R888R 265/30-295/30
LSD: Installed OS LSD
ALIGNMENT: it was around Front camber -2.4 caster 6.0 toe 0 Rear camber -1.8 toe 0.12 (total 0.24) to front camber -2.8 caster 6.5 toe 0 rear camber -2.7 toe 0.32 (total 0.64 !!!! - couldn't dial it as I skipped ML as I was planning to change suspension and Truetype could be on the card) my front grip was very good, but rear isn't, even with an added downforce, it didn't improve. I don't know about hoosier recommended alignment, but I can say the first culprit could be excessive camber-toe.
Then, it may be the hard springs at rear, as it is true-type, I saw most TT setups are a lot softer than oem style at rear, I reached out to MCA for new coilovers, they suggested 22kg front and 8kg rear.

OP, your car does sounds well setup (aka badass). Our cars are actually very similar minus your custom fuel cell and abs (nice). Any pics of your brake cooling setup?

Ideas:
-Ride height (and effects)
-Front vs. rear tire temps off, perhaps exacerbated by the amount of rear toe? (And dynamic toe?)
-I also run 1000lb fronts but run a 550lb rear spring on my true type AST 5200s (with JRZ top hats :) ).


I'd bet a nickel, though, that its due to the rear loaded tire operating in an unfavorable kinematic situation, as you said. I've noticed a big change in rear grip from ride height changes. Also keep in mind that rear toe changes with suspension position as well, so perhaps not just a camber curve issue. After making a rear rideheight change before my last track day -to help combat inside rear wheel lift on some offcamber corner exits- I was battling a lot of oversteer everywhere. I tried softening the rear ARB but absolutely hated the rear roll amount that introduced and just went back to the mid setting on my whiteline rear, made a small tire pressure change and just drove around the oversteer. Discovered one of my damper adjusters was broken and I had forgotten my spring perch wrench at home :(

From looking at your car pics sort of looks like you have SPL solid rear subframe bushings? I have those as well with the OEM'ish spacer setup at the moment.

Anyone feel like measuring hub centerline to rear wheel arch distance and alignment settings and collaborating on establishing an optimum rear ride height range?

Also: Get on the "370z Top Ten Track Records - Road Courses II" thread! The only times I've got up there, with the car as set up as it currently is, are from the Ridge MSP unfortunately.