VoodooBoot

Hello, everyone.

I have been lurking here for about a year. I have read and learned a lot, such a great community. However, there are a few things that I can't figure out.

I have a 2008 350Z that I am building into a track/canyon fun car (not a daily driver). I am a beginner when it comes to track riding or car tuning, though I love working on my car. I am currently installing suspension front and back, diff, etc. and have a few concerns about spring rates and understeer.

Goal
Goal is to have a good base that I can learn on using normal tires. I know the car would have been more than enough to learn on in stock form, but I was kind of forced to upgrade some suspension parts, so I went ahead and did everything
I prefer understeer for now until I have more experience and can cope with a car that handles more neutrally.

Mods

• BC BR true coilovers with 14/12 springs.
• Whiteline sway bar kit.
• Nismo LSD.
• Bushings front and back, subframe and diff.
• Adjustable UCA in the front.
• Adjustable arms in the back.
• Wheels: 18-inch Enkei RPF1's, either 9.5/10.5 or 10.5 squared.
• Tyres: Wanted to run 265/35 & 285/35 on 9.5/10.5, but tire selection is limited in that size. Other choices would be 265/35 & 275/35 staggered, 275/35 squared or 285/35 squared (on 10.5 wheels). I want to run normal road tires for now (PS4, FK510, for example). I am not too keen on running 10.5 squared with 285s, but it is an option.
• Rotors and pads, steel lines, RBF600.
• Seats, harnesses, 4-point roll bar, etc.
• Power: car is N/A and will stay N/A for a while. I am installing HFCs and exhaust, and will have the car UpRev tuned.

Setup
Based on what I have read around here, I am planning on starting with the following setup:

• Sway bar: stiffest front, softest rear for more understeer.
• 0.75-1" drop in height.
• About -3 front camber, -2 in the back.
• 0 toe front, OEM toe rear.
• OEM caster.
• LSD: 1.5 way, probably lowest settings.

Questions
Question 0: am I on the right path, does this setup make sense?
Question 1: Are the 14/12 springs going to be too stiff (roads are excellent around here, BTW)? Can I run them safely until I know better and can make a wise choice?
Question 2: Given the setup (springs, camber, sway bar, LSD all contribute), would 275/35 squared or 285/35 squared make the car dangerous by reducing understeer? I am almost set on 265/35 & 275/35 Pilot Sport 4 (no 4S in Europe ) on 9.5/10.5 wheels.

Thanks.

dkmura

iTrader: (64)

First of all, do you have any dedicated road racing circuits near to where you live? The only way to truly learn much about suspension setup is to test and that's simply not possible on the street. Even a lonely canyon run means you could injure yourself or someone else by taking the car beyond its traction limits. There's no way anybody else from behind a keyboard can truly give you a foolproof opinion on setup.

Your setup looks fine, but we have no way to judge what your driving skills are. Depending on experience, training, reaction time and a myriad of other factors, this setup may be too stiff or soft depending on your driving style. Having driven and raced a variety of setups, I'd go with a square setup to better utilize the tires you'll be going through. To better determine how successful your setup is, learn to use a tire pyrometer to read how the front and back of your Z is working by reading tire temps. Again, this is something for the pit lane of a track, not the street.

Since this is a dual purpose car, be particularly careful when the streets get wet, as your Z is already on a stiffer setup than stock, and could react quicker than you expect in many situations. Good luck!

djnekkon

^^^^^right on the money...


I took me more than 10 trips to the local track to adjust my bilstein coilover on the Z. I like where it sits and handles right now, but it sucks on regular driving cause its too stiff. I know I should stop it, but really like daily it now.

Blurvision

iTrader: (4)

Looks fine, just get the car out to the track and see. Make as few changes in between. Deliberate adjustment. throwing mods at the car wont help.
Also, 4 point is NOT safe. Read rule books.

13esim

At least get your car to a local autocross if you have one, it will help you feel the dynamics of your setup and highlight what can be improved. I prefer a square setup, more front grip. I don't think it's anymore dangerous on the street. (Although I've been doing skid racing also so oversteer isn't too scary) I've been running my 275/35 on 18x10.5's with my track tires all summer (I'm lazy to swap back over to my daily set with all the events im doing).

Planned setup seems decent though, I'm in a similar boat.

Honestly though, Seat time > modifications. Just get yourself some decent brakes and cooling system under control and get some laps in. Build your level of driving and modify accordingly. You'll be masking bad driving habits by modifying the car first. Modify your driving to cope with some of the drawbacks of the stock car, when you improve the car you will be able to take full advantage of whatever modification you did.

Also, to touch on the safety equipment, you'll reach a point where you will need a seat to hold you in, but do not do the other things if you don't plan on doing them all together (i.e. harness will also need to be coupled with a HANS device.)

I've been doing this for a few years now, so I am giving a perspective from growing out of the "beginner stage." The guys above are much more experienced.

terrasmak

iTrader: (8)

06platinumG

iTrader: (1)

If your running a true rear coilover in the rear a 14/12 combo is to much rear spring and you will have an over steer problem. I would suggest a 14/7 setup

VoodooBoot

Thanks for the advice!

Yes, there are plenty of tracks in the area (Western Europe).

I am trying to figure out whether I am doing something terribly wrong from the beginning (like the relatively stiff rear springs which another poster pointed out). I agree with you that it's a lot of trial and error.

VoodooBoot

I know a 4-point is not safe, thanks for pointing that out. However, I don't have a choice. I am not ready for a full cage, yet, as the car is also street-driven.

VoodooBoot

Yes, true coilovers.

That's something I have read about around here. It would seem most of the experienced guys run a much softer spring.

When you say the car's going to oversteer, do you mean it's going to understeer less, or do you think it's going to really start oversteering?

Can I just change to a softer rear spring without having the shocks revalved? I have read conflicting opinions: going +/-2 kg is supposedly fine. I'll give BC a call tomorrow.

06platinumG

iTrader: (1)

I would call BC regarding the need to revolved.

You have made a lot on changes to your suspension and as others have said you now need to spend time getting it set up correctly . Just bolting on parts can make things worse if you don't spend the time tuning.

Here are some things you can tune to get it right

Ways to Correct Oversteer
Lower front tire pressure
Raise rear tire pressure
Stiffen front shocks
Soften rear shocks
Raise front end
Lower rear end
Install narrower front tires
Install wider rear tires
Stiffen front sway bar
Soften rear sway bar
Reduce front negative camber
Reduce positive caster
Stiffen front springs
Soften rear springs

Ways to Correct Understeer
Raise front tire pressure
Lower rear tire pressure
Soften front shocks and stiffen bump
Stiffen rear shocks
Lower front end
Raise rear end
Install wider front tires
Install narrower rear tires
Soften front sway bar
Stiffen rear sway bar
Increase front negative camber
Increase positive caster
Soften front springs
Stiffen rear springs

VoodooBoot

Yup, that's exactly what I am doing. Going from 12 to 10 kg in the back shouldn't be a problem. They are going to check if 8 kg is going to be OK.

Thanks!

Blurvision

iTrader: (4)

You should run the stock seat belts. Most clubs will not let you run with a 4 point at all on a road course.

06platinumG

iTrader: (1)

He was not talking about a 4 point harness, he was talking about a 4 point roll bar .