Proper ride height for Track

03threefiftyz

Custom what?

SPOHN

Custom coilovers.

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synolimit

Depending on what that will cost, maybe you could do some fortune auto 510's.

We have similar setups, or will be when complete. Here's my survey I did for them and their response. Of course they will build them properly with valving etc.

"Based on your intended usage and vehicle, I would recommend:
15k front and 13k rear spring rates."

Attached Images

image.jpg (573.5 KB, 36 views)

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13 370z-

03threefiftyz

Meant brand.

SPOHN

Well first I love true type coilovers only. No doubt there's a slight advantage there. There's only two companies I know of at the moment that make true type for our cars. One being JRZ's. Definitely the most over rated coilover there is with a price that's flat retarted (only speaking of there entire level setups). Course they are from another country so I assume cost would be more. Every track guy I know at the track has said this to me.I just don't believe in spending crazy money for certain things.

But as another true type coilover is Stance GR+. No doubt under rated. I have track eight days on these and they are awesome. Yet they are only one way adjustable. The springs rates are 13K and 6K rear. In which on a true type setup 6K rear is the same as 11K OEM setup.

After contacting Stance they will build any setup you want for our car. So I'm looking at about $2200. This spring rates of my choice, custom valving, and separate compression and rebound with external reservoir. They have coilovers up to $3.5K.

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cossie1600

I got the 14K/11K Fortune 510. It is not stiff enough for track use only. At the middle click range, the car felt exactly like stock. I didn't notice a difference until the very top end of the clicks. Even then the car is still not stiff enough. Everything seems to be working like it should, but $2000 on the coilover was such a mistake. I should have just gone with the sway bars and camber arms instead. I am still pissed I lost my datalogs, now I don't know what the exact difference is.

synolimit

And they are OEM design? You only posted one damn pic and its super close up of just 2 shocks haha

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13 370z-

SPOHN

Weight of our cars are a big factor. Just going up in spring rates doesn't seem to be the only effective way to help with handling. I've been told by a great respected Z driver that 18K in the front is where to start. If not at least 15K.

Sways have always been the biggest gain of all my Z cars.

Besides Shamu I will have the lightest Z here with a full cage. But I'm not in any spec form of racing. Nor will I ever. I've have cut weight in areas that you wouldn't never see if you were looking right at it. My car will be corner balanced in the next few weeks for finally numbers. And I still haven't gotten my single exhaust and 2pc rear rotors.

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cossie1600

Yes they are, special order a set from a vendor here. 14/11K 510s. It fits fine and works like it should, but for $2000 I was expecting a lot more in terms of performance.

03threefiftyz

JRZ has a lot of winning pedigree, but they haven't been my choice when I dropped big money on shocks (twice). IMO, 18k would be in the upper range for a street tire car (with aero) up front. That is what I use with a 315 A6 on the front. I haven't looked at Fortune dyno's, but lower priced shocks tend to be mired in considerable cross talk, that makes them difficult to fine tune. I question how many valving options there really are for stance. They use a small shaft, etc, which would relegate them to ripping off Koni pistons and/or making their own. My guess is all they do is vary the shim stack and can pressure, then slap a "custom valved" sticker on the box.

I just had these built...I am excite:

Replacing these:

GSS138

Duh sorry, I was looking at a spreadsheet. I intend on using the SPL midlinks with spring perch on the back instead of true type like Martin. I can't decide on go with 9" then jack them up a bit or go with 10 and keep the perches low. Any recommendations on that? The perches allow 3" adjustment range:

https://www.splparts.com/store/produ...hp?pid298.html

I am figuring a 9 or 10 inch spring.

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Current Mods: Vorpal Weapon +5.

03threefiftyz

I use an OEM layout, most race springs in 2.25, 60mm and 2.5" are most readily available up to 8". It will depend on spring rate, but anything from 600-750 you will probably want a 7", 800-950 6", etc. 550 and under you might be able to run an 8".

GSS138

OK, take a look at my math on this one if you don't mind:

OEM rear spring measures about 10" at ride height. Wheel rate is about 1.61, spring motion rate I am saying is about .63.

Let's assume unsprung corner weight 675 lbs. and for arguments sake a 500 lb/inch spring.

675/(500*.63) =2.13 inches of spring compression. If I use a 9" 500 lb spring. That would mean the spring is only 6.9 inches tall at ride height.

Right?

If that part is right, then the overall ride height at the spring has moved ~3 inches lower. 10(oem length) - 6.9 = ~3

3*1.61 = 4.8. So the top of the tire would come up almost 5 inches(or body would lower whichever way you want to look at it.)

Do I have a mistake in my math somewhere? I am wondering if I measured the OEM spring length at ride height correctly. Will crawl under there tomorrow, but point out any mistake I am making there.

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Current Mods: Vorpal Weapon +5.

03threefiftyz

That's all fine, but it relies on the same static spring perch height. Any decent shock is going to have a threaded perch for the spring, which you move up. You won't lose any dynamic bump travel, even with a 7" spring. There is a considerable weight savings to be had by using a 7x2.25" spring vs a 9-10" larger diameter spring as well. I want to say the rear was a 5 or 5.5" ID spring in the rear.

ResIpsa

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