Need help eliminating oversteer

Hotrodz

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.

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Fast Intentions TT Installed and Tuned by Seb at SpecialtyZ 610whp 560tq:|Fast Intentions 3" TT-TDX|SpecialtyZ/Fast Intentions 72 Row Oil Cooler|SZ 6 Puck Clutch & Flywheel|3GsCustoms|Z1|Wavetrac|Hotchkis|Whiteline |Blitz|Fortune Auto 500|Fujimura|SPL|H&R|TK|TWM|RPM Rollbar|Sparco|Next Level Performance|TrackSpec|AeroFlow Dynamics|Pioneer|

2011 Nismo#91

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.



I wish I had my current settings handy, I almost have it right but the rear needs more work.

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GTR TT 493Whp/431lbft, Ecutek, Southbend 6puck,Quaife, RPM RollBar 4Point, R888R, JRZ RSPro F(10R/10C) R(10R/6C) 1000f500r inlbs+150inlbs Tender, SPL everywhere.Full Specs

AlWakRa

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 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.

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ValidusVentus

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.

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Mods: Dedicated caged track car, lots of things. ||| Valkyrie Autosport |||

Spooler

Just modify the rear subframe pickup points to reduce the extreme camber when lowered. It works very well. I have one.

BGTV8

A lowered Z34 has rapidly increasing rear camber in bump. If the car is rolling into a corner with no rear bar, you may find you are only getting half the rear tyre on the tarmac in mid-corner and you are trying to put power down thru 5 or 6 inches of rubber.

It may be that standing the tyre up a bit might be the solution

I have a 500hp (hubs) Z34 that runs 250/650R18 Yokohama slicks on a 10" rim and I have good balance with an OEM rear bar. I run MCA double-adjustable shocks (made in Australia by a former Australian Rally champion) and I'll check my current rear spring rate when I get home tonight (on the train on the way to work at present).
a
We found we had to lift the rear given the camber curve once we'd lowered the rear ride height to where we initially thought it should run. Eventually we found balance but our early lesson was "you can go too low" with OEM suspension dynamics

Softer rear spring will only exacerbate camber increase in roll but harder spring rate will kill squat which gives you drive and the end result will be a very twitchy car.

Spooler

Do this and you can stay low. I have a modified one on my car and it is awesome. I can hook first and 2nd. It put a stop to the top fuel burnouts. It works. Do both mods. Upper control arm and the Traction link anti-squat mod.

OptionZero

Is this why so many track folk have come to the unintuitive conclusion that a bigger front bar actually helps the car rotate?

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OptionZero Build Thread

xavier

many thanks for those first answers.

I'm convinced that the axle offset improves the rear kinematics for extreme lowering.
It will be a car with extreme settings, but it's a car that must be driven on the streets, and these extreme modifications are prohibited.

I received my 12k rear and 14k front coilovers, but they aren't adjusted or installed on the 370z; they're monotubes with rebound. From my experience with the 350z, which seems to have the same rear as the 370z, the 9k rear was too soft on bumps. Sometimes, rarely, the rear would flatten and touch the ground when there was a road defect while traveling at 50km/h / 30mph. But traction was good.

With a 12k rear, I hope it won't be too stiff. I'm planning on using Hotschkis sway bars, adjusting the geometry with adjustable arms, adjusting the alignment, changing the rim offsets, and maintaining the original tire width. with lift system on the coilovers.


Based on yours experiences:
With approximate values... with 14k front shocks.
What would the rear spring rate be (9k, 10k, 12k?) to achieve normal rear kinematics?
what needed difference in spring rate between the front (14k) and the rear (9k, 10k, 12k?)?

What would be the maximum lowering/drop, or minimum height, at the rear to maintain adequate rear kinematics?
And with what camber and alignment that aren't too extreme?

I'm planning on using the 35mm diameter Hotchkis Front sway bar, with a hard/strong adjustment.
I'm planning on using the 28.5mm diameter Hotchkis Rear sway bar with a light adjustment.
Will the Hotchkis 28.5mm Rear sway bar be too stiff (with the light adjustment)?
Would I need a different rear sway bar?

Thanks