Nissan 370Z Forum - Suspension adjustments and how they affect handling

Here is my little guide for track setup.

let me say this guide will help you with a 350z or 370z but there are some differences you need to be aware of between the cars.

The 370Z was built to be more nimble then the 350Z and the way they went about doing this was they decreased the wheelbase by 4 inches. Then on the front suspension Nissan used a few other tricks to change the feel of the car like decreasing the amount of caster from 7.6 to 8.9 degrees to 4.4 to 5.9 degrees for the 370z. This change in Caster reduces steering effort along with the reduced wheelbase makes for a car that feels far more nimble and is likely is a bit more nimble. However, to do this they had to increase the SAI from 4.3 to 5.8 degrees on the 350z to 6.9 to 8.4 degrees since caster will help promote camber gain during cornering. The 370Zs increase in SAI is a more mechanical change to how fast the suspension increases camber as it really is the measurement between the long arm and short arm in the suspension. In a 350Z the top arm is longer so it has less SAI vs the shorter top arm of the 370Z that allows for faster camber gain during compression.

Some of you might know but I do alot of track setup work at my shop and I am also involved in a few professional racing efforts. Let me say that I have done track setup on everything from Grass Roots to Professional racing and unless its a time-attack car setup or AutoX it always has a general profile that will benefit 95% of you but certainly changes on venue/conditions/etc but I want to give a few general guidelines and things I see all the time that keep people from getting that extra edge. This is the way I think about it in my own head when I get a new car to setup.

First, I want to tell you that everything is a compromise and I am talking about generalities here. I could counter my own way of thinking very easily. So to talk about tires and a few general guidelines. The very first being that the grip level of the tires you are using is going to effect setup. So if your running a very sticky compound (Short life) generally speaking your going to be more on a harder setup and if your running on street tires your going to be running a softer setup. I generally error on the side of soft vs hard as when you get to hard in your setup mechanical grip suffers and things like curbs can really start unsettling a car.

Second, I want to talk about Camber and how it is going to change depending on situation. I can tell you right now that an acceptable range is from -3.5 to -2.2 front and -2.5 to -1.5 rear. Your spring rate and your tire compound will be primary factors in your camber levels. I have yet to come across a situation yet that has required a higher rear camber then front camber.

Third, Caster because it goes hand in hand with camber.

Since camber changes to negative on the loaded wheel and positive on the unloaded wheel. I tend to keep Caster consistent until I can get good tire data. Also, if your one of those guys running crazy amounts of camber because that is what your seeing right now from data. It might be time to think about making a drastic caster change to reduce the need for crazy camber numbers. I have also noticed if you are seeing increased front grip with larger front sway bars its highly likely its time to increase front caster.

This is one area I think the 370Z can really be improved. I have not done alot of testing and being late to the setup party I don't really know what B.J. and the guys have tried. However, there could simply a limitation where it no longer helps as camber gain gets to dramatic on the outside/loaded tire and reduces grip. In that case take B.J.'s advice and add more front bar! I do not think the 350z suffers the same problems as a result of different geometry.

Fourth, lets talk about toe as its one of the best ways to make changes to your car. Rear toe is going to depend some on parts you have in your car. Front toe on a race car generally going to keep it pretty close to zero but some drivers prefer a toe out for more turn in. The rear toe we always leave some toe in to keep the rear stable under braking and under acceleration off the corner. A zero toe with soft bushings can turn into toe out on acceleration and make for some very interesting dynamics.

Fifth, Shocks! If you are running a full remote res setup with the ability to adjust pressures do me a favor and please buy yourself a nitrogen bottle/reg and a dry-break or whatever it is called tool. Keeping shock pressures at a constant pressure from weekend to weekend will help you. I can't tell you how many times I have seen very nice aftermarket shocks that were way uneven or way low on pressure. I always keep an eye on the pressure inside the shocks before the start of a weekend.

Sixth, Corner weighting your car. I always suggest this be the very last thing you worry about in your setup and I would only start to mess with it after you get a general handle on your car. If you do decide to get a corner balance then remember that you need to have at a minimum. adjustable ride height with coilovers and adjustable swaybar endlinks. When I do corner weighting the individual numbers are not important. The important numbers to me are the cross weights so what is the split from RF/LR or LF/RR

I hope that helps.
Also, remember if you have any questions about your setup feel free to E-mail me at shop@metricgarage.net. You also can always reply to this thread and like us on our facebook page www.facebook.com/metricgarage.net