Nissan 370Z Forum - Spring rate help?

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- - Spring rate help? (http://www.the370z.com/track-autocross-drifting-dragstrip/94946-spring-rate-help.html)

Lincoln is too far from SD when there's no jacket at stake.

Quote:

Originally Posted by j-rho (Post 2929701)

Sure every car is different, but increasing front spring rate with no other changes (increasing the ratio you mention) will make the front tires do relatively more work in a corner, which as a primary effect, shifts balance towards understeer. Your generalization is backwards of the general truth. If you want to make a case the general truth does not apply for some reason to the Z, you need to be able to explain why. You also need to be able to separate a discussion around bump handling (where shocks come heavily into play) vs. handling balance at steady-state limit cornering.

I encourage you (and anyone following along while scratching their head) to get a basic education in vehicle handling dynamics - Herb Adams, Fred Puhn, Paul Van Valkenburgh all have fairly accessible texts on the subject. A few $ for a book and a few evenings of reading, and you'll be much better equipped not only to understand what's happening with your own car, but to help others in their pursuits.

fair enough and I agree with you, but feel my point is being missed a bit, as I am not addressing over all vehicle handling dynamics, weight transfer, tires, or anything else. All I am saying is this:

There is a ratio between front and rear ride frq that will tell you if the car has a tendency to oversteer or understeer.

If you want to change that tendency-change that ratio.

To redo my example, let's go back to our OEM rates:
I am using 392 front springs, and 440 Springs (listed OEM rates I could find)
They produce a ratio of:
1.6334/1.8563 = .89

Do you not find it interesting, that using completely different spring rates, this same .89 number is produced by just about every post market spring kit within a few decimal points?

Swift Spec-R's claim 10K and 10.5K so approximately 560F 600R
they produce a ride frequency on the same car of:
2.0115/2.2427 = .89

Much stiffer springs, totally change the way the car handles, so why is that .89 ratio still popping up?

All I am saying is that .89 is not a coincidence and was put there by your car manufacturer, and by Swift, and Eibach, and by every other lowering spring I can find rates on.

I should have given up when I said "I give up"...

Quote:

Originally Posted by GSS138 (Post 2929736)

By itself, it can't begin to tell you that.

What you might be able to say - if you had a neutral car, and then you increased front spring rate, or softened the rear spring rate (increased that ratio value), the car would probably tend to understeer. But that's the opposite of what you're saying.

Quote:

Originally Posted by GSS138 (Post 2929606)

I Completely agree with this, but I am not counting grip, sway bars, or anything besides the motion ratios, corner weight, and spring rates. I am just talking about a natural frequency that the car exhibits when it goes over a bump. It's something that is there by the manufacturer on purpose in every car. And if you take those freq and divide them, I am completely speculating here, but I will say that 95% of the cars on the planet rolling of an assembly line are in the range of .80-.90.

If you calc the rates for every single post market spring kit or out of the box coil over solution, you will either get a number between .80 -.90 (Understeer)
or you will get something in the range of 1.13-1.25 (looser rear end).

(Assuming close to OEM un-sprung corner weights)

Swift Spec R= 2.0115/2.2145=.90

Tein S-tech= 1.682/1.87 =.89

Nismo T2 motorsports springs = 2.0821/2.4224 = .859

Now let's look at some popular performance coils

Tein Flex = 2.2035/1.9833= 1.11

Stance GR= 2.2035/1.9624 = 1.12

Megan Racing 2.0115/1.6650 = 1.21 (loose!)

Edit:

Synolimit's Setup 2.6880/2.0361 = 1.32 (have fun cowboy)

Our OEM(non nismo) 1.6334/1.8563 = .89

This isn't a coincidence!

Again, it doesn't make your car go fast, has nothing to do with grip, doesn't get you trophy girls. It's just a baseline calculation that you can use to have a reference point for what you can expect out of your spring, your motion ratios, and your corner weights to do. Of course putting the tires, driver, sways, fuel, etc on top of this number changes everything. But it's nice to have a solid starting point :).

This PDF explains it better than I can: Freq of Ride rrates

https://m.youtube.com/watch?v=q5pESPQpXxE

Quote:

Originally Posted by 03threefiftyz (Post 2929627)

Oh...keep in mind syno is not running a spring in the bucket.

Correct. True type as of today. Well maybe not wtf??!!!

Sorry OP

https://m.youtube.com/watch?feature=...&v=l5i_kyW7_Y4

...And taking setup advice from DOT street tire AX guys on a track car is dangerous. :icon18:

Quote:

Originally Posted by 03threefiftyz (Post 2929708)

j-rho,

Mo CAM with this please....
https://farm4.staticflickr.com/3853/...2a4ca503_b.jpg

I like this purple car.

Quote:

Originally Posted by GSS138 (Post 2929991)

I like this purple car.

:icon14:

Looks blue to me.

Ok so after all the other diversions, I still have a couple fundamentally-simple questions (one of which I already asked!):

1) Will I need to use shorter springs if I switch to a significantly stiffer spring and want to keep ride height and stroke about where it is today? Or should I basically plan on ordering the exact springs I have today, just in a different rate value? What would a normal person that knew what they were doing tend to do? :)

2) The rear sway: it's a given I at least need to cut back to the stock bar. What about just dumping the bar altogether? I know others have dumped the rear bar and been happy in 350Z's, but I suspect this was in combination with an upgrade to stiffer springs all around. What's the worst that could possibly go wrong* if I dump the rear bar and fail to do (insert some other unknown thing that needs to be done at the same time)? Would the car get unstable in some way that I'd really hate?

* - https://www.youtube.com/watch?v=20KJhBX9xtE

Have you spoke with Z1 on what spring rates they use on kleemans car? I would just start with a popular track inspired setup then refine it from there.

Well I've got a good idea on ballpark spring rates at this point (and a little confirmational math to do before I pull the trigger, which will be after I've dealt with the rear sway). Keeping in mind that I don't want to have to swap springs constantly at this stage for different tires and don't want to be too unstable on wets or r-comps, I'll probably shoot a little lower than the track specs listed in this thread, but still considerably higher than where I'm at now. Something in say the ballpark of 900 and 700 - which would be approx the same ratio of raw spring rates as what I have now, with both ends boosted by about 30%. I know there's more math to be done than that, but it's a starting point guestimate at this stage. I'm gonna go measure the suspension later today or tomorrow so I can make some easy conversion factors for F/R spring rate -> F/R frequency.

Quote:

Originally Posted by synolimit (Post 2929824)

Correct. True type as of today. Well maybe not wtf??!!!

Sorry OP

https://m.youtube.com/watch?feature=...&v=l5i_kyW7_Y4

Great sound effects! :icon17:

Trying to learn from this thread, and my mind is going hu.............................

good to see the Z track people putting enough 2 cents each to get a informative thread into page 4 :D