Coilover upgrade questions.

[dogunbound]

After having a scary track day (110MPH slide off into the grass), I am starting to want a much stiffer set of suspension. Even my instructor on board said the car probably would not have stepped out on me with a tighter setup.

There are SO many opinions on this, that at the end of the day, I know I will just have to pick one and hope I like it. Regardless, there are a few questions I have.

1. What are the stock spring rates in the performance model?
   1. Looks like this is still unanswered https://www.nissanzclub.com/forum/threads/oem-nismo-2024-spring-rates.2635/
2. How much will I need to adjust the spring rate measurement from bucket springs to true coilover springs for a comparable measurement?
3. Are any of these options unreliable? I am looking for something that should perform exceptionally well for 5 years would be the goal. Failures after 8 years would be "expected". The KWs are my upper limit tbh. I do not want to spend 7k for a split oil reservoir suspension setup. If you have other recommendations, please let me know!
   1. Billstien B16 https://www.rockauto.com/en/moreinfo.php?pk=6609676&cc=3454543&pt=10922&jsn=709
   2. Fortune Auto 500/510 (Probably 500) https://martiniworks.com/products/s...rz34-separate-style-rear-500-series-coilovers
   3. BC racing DS https://martiniworks.com/products/s...es-coilover-22-nissan-400z-true-coilover-rear
   4. KW Variant 3 https://www.z1motorsports.com/nfs/kw/kw-2023-nissan-variant-coilover-kit-p-44950.html
   5. z1 coilovers https://www.z1motorsports.com/z1-pr...-nissan-pro-true-style-coilovers-p-43107.html
4. What spring rate is known to not be dailiable by most people? As for the z1 coilovers, I see they are 16k front 8k rear. That seems quite aggressive, no? I personally do not care for how soft the stock suspension is. I used to drive an 03 camry with BC racing BR coilovers (6k front 3k rear), and that was incredibly comfortable even at the tighter rebound/compression setting. The Z's suspension was a legitimate downgrade IMHO.
5. Are swift springs worth the hype?
6. If you have bought custom suspension, what spring rates are you running? Additionally, are you tracking your vehicle?

 

[Who.Am.Eye.2716]

Im not able to answer your questions on suspension.

Did you keep the stock tires when you went on track? Switch to High Performance Summer Tires for those track days. I been on 2 open track days with Falken RT615K+ tires and I had no shimming at 135ish mph. Thats when the govenor kicked in

Now, the brakes are the weakest point. I was getting brake fade, to the point I had to downshift to slow down enough to take turn. After that, I reduced to 70% throttle

 

[Apex_Z]

I am not sure about the spring rates for our cars specifically, but they are pretty soft. Stiffer springs and damper will make the car more responsive, and any of the known brands will be good. If you are going to street and track the car, pick a middle of the road option spring rate wise. Typically a good approach is to reach out to the manufacturer and ask for a recommendation.

The next part is some insight about track driving. For reference, I have a background in professional racing as a driver and engineer.

New suspension isn't going to prevent you from running/sliding off the track. Your tires are the primary grip contributor, and your driving technique is more important than any other factor as long as everything is in good working order (brakes/suspension, etc). Understanding this is important to keep your confidence and expectations realistic, which will help keep you and others on track safe.

 

[kevinbonds]

I would not change too much to fast. Unless you are a major track rat, I would go with tires and a proper track alignment. Then hit a few more track days and see how it goes. Then, determine what's needed next. Coilovers are not always the answer, they take allot of effort to get dialed in to give you an advantage on the track.

 

[dogunbound]

I've got the idea that the issue was skill. I was looking for an excuse to swap out the suspension tbh lol. My slide off was caused by me being emotional and wanting to run out on the track. Getting impatient with traffic in front of me. Lastly not warming my brain up slowly enough and just absolutely sending it out of the gate as soon as I could.

I've already got 200tw tires mostly for longevity on track rather than for the performance. My suspension is:
Front camber: -1.5
Rear camber: -2.1
Front toe: 0
Rear toe: 0
It is setup to try and be as friendly to the tires on track as I can. I cannot camber out any more. Also the front camber is not adjustable.

What I've also done are high performance brakes. Gloc R18 fronts, DTC Hawk 70s Rear. Again, this is for safety and longevity on track, not necessarily because I want to run track pads. I honestly would rather not as it cakes everything in brake dust.

The last thing done to the vehicle is different fluids.
Brake fluid: RL 600 (394 wet, 601 dry)
Engine Oil: 0w30 (Thinking of using a 5w30 instead since it is more available and stable of an oil)
Transmission Oil: 75w90
Diff Oil: 75w140
Again for longevity on track, not for performance.

 

[Who.Am.Eye.2716]

Mental is definitely a big part. I was in the same situation when I was on track 10 yrs ago. There was this one driver that was intentionally blocking me from passing. I was faster in corners and on their bumper, but a little slower down the straight. I almost let my emotions take over, but decided to hit the paddock and turn back on track. This gave me a half a lap behind the douche and I was able to get back into the groove. After the session, I went and talked to an Instructor and explained. It went well the rest of the day

Transmission Oil: 75w90
Diff Oil: 75w140

Sorry to side track your thread

What brand and quantity was used for Diff and Trans?

 

[dogunbound]

What brand and quantity was used for Diff and Trans?

for the addendum service manual. It gives you all you need for how much fluid you need.

As for the brand. I don't think it matters too much, but this is what I ran last time.
Trans: Motul Gear 300LS
Diff: RedLine GL-5
It's important to only use GL-4 in the trans, and GL-5 in the diff.

In the google drive link, it has quantities:

 

[Hernandooo]

I've got the idea that the issue was skill. I was looking for an excuse to swap out the suspension tbh lol. My slide off was caused by me being emotional and wanting to run out on the track. Getting impatient with traffic in front of me. Lastly not warming my brain up slowly enough and just absolutely sending it out of the gate as soon as I could.

I've already got 200tw tires mostly for longevity on track rather than for the performance. My suspension is:
Front camber: -1.5
Rear camber: -2.1
Front toe: 0
Rear toe: 0
It is setup to try and be as friendly to the tires on track as I can. I cannot camber out any more. Also the front camber is not adjustable.

What I've also done are high performance brakes. Gloc R18 fronts, DTC Hawk 70s Rear. Again, this is for safety and longevity on track, not necessarily because I want to run track pads. I honestly would rather not as it cakes everything in brake dust.

The last thing done to the vehicle is different fluids.
Brake fluid: RL 600 (394 wet, 601 dry)
Engine Oil: 0w30 (Thinking of using a 5w30 instead since it is more available and stable of an oil)
Transmission Oil: 75w90
Diff Oil: 75w140
Again for longevity on track, not for performance.

I think you got your cambers backwards lol

Also, try 5w50 or thicker if you're going to track it, maybe add the CZP oil cooler your engine will thank you for it

 

[Who.Am.Eye.2716]

Thats the best service manual I have seen. Thanks

 

[trackratZ]

Looks like you have the proper preps for at least your first track days, critically brake pads, hi-temp brake fluid (you meant RBF600) which are the stock non-Nismo Z's biggest issue, 200tw tires, and other fluids. The one huge help would be a an experienced instructor familiar with that track, worth hiring! Each org should provide instructors that's relatively reasonable.

Good luck next time and keep tracking

 

[Maximum_Jars]

I'm a bit late to the game on chiming in here, but the situation can often be really complex.

On the simplest version, I agree with everyone above that driver error/skill can fix pretty much any issue on track. IE: drive to the conditions at hand and to the capabilities of your car and you'll rarely have an issue.

That being said, there are several factors than can contribute to the situation and make it worse. My example comes from my very first track day with the Z. Taking corners at high speed for the first time on an unknown track for me felt unsure and just downright scary. I had set the z up to have a little over-steer condition but this was something different and many, including myself, simply chalked it up to being new and needing to learn. After all, the z and the 370z before it is well known as a snap-oversteer prone car. I also had an off on that first foray and figured I had a lot to learn with regards to handling a high power, heavy rwd car. After doing some digging on it I had my alignment checked and it turns out the shop that did it completely missed the mark to the point that I had toe out in the rear which is an exceptionally dangerous thing to have on a rwd vehicles in any scenario. Once that was corrected it made a massive difference not attributable to driver skill.

In terms of your situation, there are lots of questions to ask:

Is that turn more difficult for you and if so why? Is it the line you're taking, is it over-driving, is it poor habits during turn-in/mid-corner/exit? If any of the above apply, it probably will be the cause and is the direct area you need to consider fixing.

Is it car set up? Did you oversteer and spin off the track or did you plough forward and understeer off the track? How bumpy was the track? Was it a compound turn or a single wide sweeper? Did you make a correction during the corner and unbalance the car to cause it? How about elevation change, did you go through a dip, or over a crest?

My mind immediately goes to the zero rear toe as a point of concern and potentially the additional rear camber vs the front. Technically it's not in the danger zone but part of the problem is that bump steer can cause changes to toe-in/toe-out. That means while you're targetting zero static, the reality is that under a bump you're getting toe-in and on the rebound portion, or elevation changes (cresting a hill), you're gaining toe-out. Toe-out during a corner provides less maximum grip than toe-in. Nevermind the fact that bump steer makes the steering inputs erratic, less sure, and decreases grip alone. I'd highly recommend a touch of toe in for the track. Your wear won't be more accelerated than your shoulder wear will be from hard cornering. In fact, you'll likely find it will even out your tire wear while gaining you grip in acceleration, braking, and mid-corner. This might not fix the problem if the issue originated from the driver, but it may help the driver in some of the more difficult elements on the track. Be careful when making changes to one end of the car of course, it will change grip levels and may affect your oversteer/understeer balance.

Now for your question about coilovers. Will they help? Assuming they're set up correctly (follow the maker's specs to start and you'll be fine) the answer is yes in a lot of the above scenarios. Stiffer springs will reduce apparent bump steer, will flatten out the car, and cause less suspension geometry changes. So this means you'll likely gain more grip in the corners (to an extent - after a point stiffer springs actually decrease mechanical grip given no other changes). The coilovers will also communicate faster in terms of feel for what the car is doing, so you'll react faster and the car can handle your corrections faster - it will help you as a driver. It will also handle your corrections better without becoming upset, so if you need to get around traffic or debris in the road for example. There are a lot of advantages to coilovers, but you don't need them to be a better driver and to maximize your times on track. They just make it easier to an extent. Of course there are some drawbacks like comfort (unless you spend a lot) and the suspension can be less forgiving on input mistakes, large curbs, large bumps, potholes, etc.

Remember that just because I, or someone else, thinks you may have a car set up concern, it may not be a concern for you if it fits your current driving style and preferences - so it's best to work through the questions yourself as you go.