I've always had this questions in the back of my mind on this subject. I've seen a number of set-ups that the divorced set-up vs true type run close to the same spring rates. And some of this is from the companies that make true type. And suggest a spring rate too high from what Bobby is saying. Which I believe too. Thanks Bobby to bring this to light. :tup:

I am really happy that this is helpful. I really lucked out on finding someone that understands this stuff and can make sense of it to someone that knows enough to be dangerous and mean that literally.!:eek:

I remember reading about this

Where the spring is located is physically changed when u go from OEM type to true type
Since the OEM spring rates are based on oem locations, and the tuners are using that same geometry to do their math, it stands to reason that changing that spring location changes the geometry and requires new math to find ideal spring rates

I wouldn’t say geometry has changed. The arc of which the arms move are still the same. There’s no change to how camber and toe build up as the springs get compressed.

It’s the physics that changed. Imagine using the same spring, moving the spring outward to the hub makes it much harder to compress the spring, therefore a lower spring rate is needed to compensate.

Nailed it, as this is what I have read and was explained to me!:tup:

One thing to keep in mind is that while the geometry doesn't "really" change, it can be slightly different with respect to the angle the spring is acting on the suspension arms. This is why when calculating suspension numbers like motion ratio, wheel rate, and suspension frequency, you have to do some trigonometry with the angle the spring is at.

:tiphat:

I remember my first time reading a discussion about this on a wrx forum, it went over my head completely. Looking forward to the results. This thread makes me think twice about my own rear rate.

It is agonizing for me as I want to get the info, make the adjustments and test them but the testing will have to wait until my motor is built and installed. I still have ETA on delivery.:ugh2:

I should have corner weights when they set the alignment on my car. They are supposed to check them since I am corner balanced. I will get them to you when/if that happens.

Honestly, you should be ordering your spring rates based on how much downforce your car is going to produce at certain speeds. A bucket type coilover system, the spring is far closer to the hinge, so it needs a lot more spring weight to compensate. Running a true style, without aero, 6k is on the mark based on my research. I might want to bump it up to a 7k to compensate for your aero. Just my 2 cents. It would probably settle down the rear a lot powering out, under braking and on bumpy surfaces or rumble strips.

It sounds dumb, but chassis tuning on Forza, I drop the damper and spring rates a lot to settle rear down and add a bit of toe in. It's not real life, but I'd imagine the logic is the same.

Edit: Totally wrote this blind and happy others kind of confirmed my thoughts. I run stock Nismo aero and Swifts. I'm basic lol.

I feel like your motor build wait has been going on for at least 3 years.. cant imagine what it's like for you lol

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You are not wrong! That being said if your suspension is not set properly the influences from the aero can have significant impact on handling and that is why he stated that with the spring rates I am currently running and the downforce from the wing will cause the car to oversteer significantly because you are loading the rear of the vehicle and unloading or adding lift to the front of the vehicle. The fix will allow me then to do aero tuning that I need to maximize front and rear aero.

So my initial question to Danial at Awesome Performance Racing was did he think adding front splitter diffusers would be beneficial with my current setup and the whp I will be running in the future? He initially said no and then after I sent him information on my coilovers, he provide the information I posted and he asked me for some data so he could figure out the best spring rates for my Z. He specifically asked for corner spring weights and for me to give him the spring lengths front and rear when the car is unloaded and then compressed as this all matters when considering spring weight and drupe. The other thing to consider is that if your wheel rates are off you can over work your rear diff. This maybe one of the reasons some have issues with overheating their rear diff at the track or on canyon roads.

I figure if he wants to help me fine tune my car setup I am going to listen and take in all the information I can. His credentials and the people race team he works with speaks volumes. Oh and he said the diffusers would be beneficial.

LMAO it does feel like three years but it has only been since November last year.

Then help me out

This may be the first time I rated a thread 5 stars un-ironically.