G37 Track Set Up. Oversteer Help.

2.2Lude

Hey guys, I wanted to see if anyone has any experience or insight to help me resolve an oversteer issue I'm having with my G37 sedan on track. I know it's a longer wheel base than the Z but figured the majority of the set up should be the about the same.

In this video at points 4:20, 6:20, 9:35, and 12:18:



In this video at 2:25 I did lose it. I'm not sure why the backend came around soo late but I think I made it worse by getting on the throttle while trying to correct it.:
(youtube is still processing the HD version as of the time of this post)



Here is the set up relative to the issue:

- Tanabe Pro CR Coilovers 10k Front/9k Rear. Pretty damn soft dampening.
- Eibach front bar set to full stiff
- Factory rear bar
- Square 18x9.5 +45 PF01's with square 275/40 MPSS's(+35 front with spacer, still +45 rear. Rear spacers/studs to go on soon)
- G-Loc R12/R10 combo
- Bell Raceworks diff brace
- Kinetix front camber arms(Will be coming off soon, they aren't meant to add negative camber without modifying them)
- Aim for 38 hot front/ 36 hot rear PSI

Fresh alignment specs:

Front Left/Right camber: -.9/-1.1
Front Total Toe: 0
Front Left/right Caster: 5.7/5.8

Rear Left/Right camber: -1.5/-1.6
Rear left/Right toe: .11/.13
Rear total toe: .23


About myself: Very much a newbie with about 10 HPDE's under my belt and only 6-7 in the RWD G. I built some bad throttle application habits by driving with traction on that I'm working on slowing down and unlearning now. I've taken one skidpad/car control course which was beyond helpful and getting me off the right foot as far oversteer correction is concerned.

Problem is I don't trust the car to remain predictable with the traction off/yaw sensor bypassed. I know I carry more speed than I should at times into some corners but the rear end wants to come around even when I slow my entry speeds down.

I was working with a coach over the weekend who drives a Nismo 370z and he noticed the same thing. The car just feels sketchy and it's really slowing down my progression as a driver. I'm not chasing lap times just trying to become a better driver and hoping to eventually get into time attack stuff down the road(not in the G). With that said my current PB at Laguna Seca is a 1:52.0 and I can consistently run 1:53's.



Here are my thoughts:

1. The car isn't corner balanced but the ride height is even front/rear at the pinch welds.

2. Could the +10mm front to rear wheel stagger be causing this kind of issue.

3. +2 psi Front tire pressures compared to the rear helped a little.

4. Too much traction upfront compared to the rear is causing the rear to be loose. Should I run a staggered tire set up to reduce some front grip? I really don't want to do that. Maybe set the front bar to soft or even go back to stock bar?

5. I wanted to add more negative camber up front(why I got those camber arms, even though they actually reduced my max negative camber compared to the factory arms) but that will only increase front grip and make the oversteer worse?

6. Maybe add some front spring. 10k front/9k rear might be too close in relation. Going a little passed my knowledge base.

Rjk370z

Maybe try a staggered setup. The square setup will make the car oversteer more. I thought on the track you want the car to oversteer. Maybe removing the rear sway bar. This is just my opinion some more experienced track guys can chime in.

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2.2Lude

That may be a solution. I followed the advice of experienced track guys on how they set up their cars but that might have been the wrong approach for my driving style. I'm thinking I prefer a touch of understeer at least until I get more comfortable with oversteer and my ability to drive at the limit.

fryzia23

For starters your springs are too soft with race pads. Too much weight transfer under braking causing nose dive and rear to walk. Adding rear wing would help keeping rear more stable as well.

SonicVQ

We have the exact same G37 Sport sedan (even same color!), but mine is a year older.

I have done a few HPDEs in my stock G37 and it is rock solid. It never did anything that surprised me and every corner was entered and exited knowing what to expect and it was very easy to steer with the throttle, when I wanted to. Miles of smiles

With the suspension mods you have done, you have added a lot of variables.
• Changed the front scrub radius by 35mm
• Changed the front track by 35mm and the rear by 45 mm. Since the track has been widened, there is more leverage on the suspension, so the effective wheel rate is softer/lower.
• Different spring rates and compression/rebound damping.
• Possibly different spring preload.



Items I would look into:
• Suspension travel. Is the rear hitting the bump stops when on the track? If it does, the wheel rate goes way up, and you loose traction.
• With a 275 rear tire, maybe -1.5 degrees is too much negative camber and not all of the tread is on contact with the road. As I recall, the G37 has a good rear camber curve and doesn't require much negative camber.

Bottom line:
If your car oversteers more than you want, you need to decrease the rear roll stiffness or increase the front roll stiffness.


Also, this may be of interest to you:
http://infinitig37.com/G37-BC-Coilover-Review.html

SonicVQ

First video at 1:52 that is some instant snap oversteer in mid-corner!
Makes me think if the rear ran out of suspension travel.

Put some tie wraps on the shock shaft to check the maximum shock travel.

OptionZero

Throw those arms away
Call SPL
Buy all their arms

Sell the tanabe
Get some fortunes with a higher rates

Crank up the camber all around

My guess is the softness suspension is causing a lot of weight transfer mid term, overcoming available grip already compromised by the weak alignment

But I’ll let the track rats chime in

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cv129

I think SonicVQ is onto something here.

Spring Rates

Isn't a 9k spring rate equate to around a 500lbs/in? That's same as the OEM Nismo 370z rear, which would be quite soft for the sedan. Combined with the shorter travel, up-sized tires, you may just be suddenly hitting bump stop, infinitely increasing the rear spring rate in an instant.

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Spooler

If you are running a square setup you need to disconnect the rear sway bar and see how the car does. Most people with a square setup will not run a rear sway bar because of the issue that you have.

Hotrodz

You need more spring up front rear okay, get some trackable coilovers. If you are running r compound tires you need to shoot for tire pressures between 34 and 36 hot. Your ride height should be within an 3/4 of OEM. Get all SPL suspension components as mentioned. Camber in the rear is okay and you need at minimum -2.5 up front. As was mentioned, the brake pads you are using are very aggressive and should only be used with r compound tires or slicks. Xp 10 and 8 are just fine. I ran them on my boosted Z with r compound tires even when I got to HPDE 4 and was carrying some speed.

If all else fails or you don't have the money to get your suspension setup properly, go back stock or close as possible. Then change one significant component at a time.

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2.2Lude

These Coilovers are designed for street comfort so that does make a lot of sense. Problem is even when I brake earlier and the car is more settled before turn in the car still oversteers.

Yeah I know the SPL's are the be all end all but they're just extremely overkill for my use case. The car is a daily that I want to use to get better as a driver on the track with. I've spoken with a few guys that race in a Nissan series in Socal that use these arms(modded) with good results. I'm not building a race car so I don't think mind giving up caster adjustment and spherical bearings/joints for cost/comfort. Basically trying to build a well balanced car.

With that said I'm not adverse to stepping up the spring rates a little to get off the bump stops if that is what's going on in the rear here.

2.2Lude

Thanks for the insight! I will say that when I was on stock sport springs and shocks with square 245/45's and the Eibach front bar the car didn't feel as lively as it does now. I had much less experience then though and couldn't really "feel" what the car was doing + my pace was much slower.

I'll try and see if I'm hitting the bump stops in the rear as you suggested when I get some time or during my next track day.

The car snap oversteers at T10 at Laguna a lot lol.

I've attached images of the rear suspension to see if it helps any. The rear springs are progressive from the looks of it and rear shock body is shorter with what appears to be more travel. I also keep the rear at max ride height allowed which equated to around G2F 26.75". I'd like to go higher but that is max adjustment available.

Attached Images

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2.2Lude

Bumping up the tire pressure up front did help so I feel like more front spring or bar would also help but I don't want to be chasing my tail. I want to add more negative camber upfront(-2.5) to help tire wear but It will just give me more traction up front relative to rear making my current oversteer issue worse.

I was originally wanted to go with the R10/R8 combo but the Z1 guys said while those compounds worked well for the Z, they weren't enough for the heavier G. Might need to step back down.

The "best" tires that I'll put on this car will a 200tw "cheater tire". Something like a RS4 or N'ferra. No R compounds are in the plans for this car.

OptionZero

I'm sorry that's ********. You can't post in the track section asking for advice about suspension and then NOT get SPL stuff because you're worried about cost comfort. The only reason not to use the best arms available is if you're in a racing series that specifically prohibits it

YOU CAN TOTALLY DAILY A CAR WITH SPL ARMS - i dont know where the stupid assumption that adding spherical arms will suddenly make your car unlivable come from

spring rate/damping and tires have a far bigger effect on how your car will feel


your sensibilities are way too soft. if you want a car that actually is trackworthy, get over your ******** and do it right
without proper alignment capability, you're wasting your ******* time

why bother coming here asking for help if you're gonna turn it all down because you wanna half *** this ****? Why are you wasting money on track time at all if you aren't even going to do something as simple a real coilovers and alignment?

this is sad

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Hotrodz

You also might soften your front bar as well. That will induce more understeer.Those tires are not cheater tires. The rs4 is good tire for endurance and getting more session in. The cheater tires are AO52, Falken 660 and Eagle r3. Really doesn't matter as you need to get the balance back in the car.

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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|