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GC 280Z is now too low.


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Not sure what is going on. I sectioned the struts per this site (about 1.5" taken out), 6" collars, 10" 150# springs.

 

To raise the body of the car I am threading the collar on the sleeve UP (which compresses the spring) which lifts the body of the car. Unfortunately I have the collar 6" + up from the perch and the car's frame rail is still too low (1.5" or so above the ground). The front control arm is below parallel (which I read is bad)

 

If I use a jack to raise the car up the height I think is good the wheel well gap gets too big.

 

Confused :(

 

 

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If I use a jack to raise the car up the height I think is good the wheel well gap gets too big.

 

Confused :(

This means your tire diameter is too small.  Get the tire diameter that gives you the body height and gap that you want then fit the suspension.

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Why are you at 23.1"?  Stock rolling diameter is 24.7".

 

You have 15x9's, there are plenty of tires that will get you up to 25-in., you are just going to have to have some sidewall.  Sounds like you are running a stretched setup (23.1" rolling diameter).

 

215 60 R15s puts you are 25.1 and there are 22 tires list on Tire Rack.

Edited by ktm
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Why are you at 23.1"?  Stock rolling diameter is 24.7".

 

You have 15x9's, there are plenty of tires that will get you up to 25-in., you are just going to have to have some sidewall.  Sounds like you are running a stretched setup (23.1" rolling diameter).

 

215 60 R15s puts you are 25.1 and there are 22 tires list on Tire Rack.

 

Thanks, so the 60 series isn't too tall?

Edited by kerrys914
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The 10 " inch, 150 lb/in springs may cause you a problem as well.  The sprung weight per corner is around 600 lbs, so the springs will compress about 4 inches with the car sitting in the driveway.   When you hit a bump you will try to compress the springs an additional 2 - 4 inches.  Unfortunately, the springs will stack solid before you can get that much more travel.  

 

The free length that you need is related to the rate of the spring. The stock springs were about 100 lb/in and had a free length of about 15 inches.  When I ran my car on the street, i had 250 lb/in springs with a free length of 10 inches on the rear and 200 lb/in springs with a free length of 12 inches on the front.

 

Currently, I run 500 lb/in on the front and 400 lb/in on the rear with an 8 inch free length (no longer a street car).

 

If you want to stay with 150 lb/in springs, you should try for at least a 12 inch free length.

 

BTW,  I have my old 250 lb/in springs (2.5 diameter coil-overs) for sale cheap.

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I just looked at the Eibach catalog, where they publish all the spring information.

 

http://eibach.com/sites/dedevperformance-suspension.eibach.com/files/download/ers_catalog_global.pdf

 

The load at block height for a 10 inch, 150 lb/in spring is 972 lbs and it total travel from free length to being fully compressed is 6.48 inches.  With these springs you will only have ~2.5 inches of travel before the springs stack.

 

For a 12 inch, 150 lb/inch spring the load at block height goes up to 1171 lbs and the total travel increases to 7.71 inches.  With these, you will have ~3.75 inches before the springs stack.

 

 

For a 10 inch, 250 lb/in spring the load at block height is 1569 and the total travel is 6.28 inches.  With these, the springs will compress about 2.4 inches for the 600 lb static weight per corner.  You will have  about 3.9 inches of travel before the spring stacks.

Edited by 74_5.0L_Z
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Im confused when you said you sectioned the struts per the instructions on this site...

 

 What was the final measurement from the inside of the strut tube to the top of the threads? 

 

The front should have the overall length of the strut tube (13.375" to 13.500")

The rear should have the overall length of the strut tube (14.938" to 15")

Edited by proxlamus
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I too am running a 25" tire.
 

25" Tire Diameter

165/80R15 = 25.4X6.5R15
185/70R15 = 25.2x7.3R15
195/65R15 = 25x7.7R15
195/70R15 = 25.7x7.7R15
205/65R15 = 25.5x8.1R15
215/60R15 = 25.2x8.5R15
225/60R15 = 25.6x8.9R15
265/50R15 = 25.4X10.4R15
275/50R15 = 25.8x10.8R15

These sizes are in range.
https://tiresize.com/height-chart/
post-47984-0-75532100-1459044149_thumb.jpg

post-47984-0-56652200-1459044150_thumb.jpg

Two cars here both running 275/50/15's. 10mm isnt enough to get upset over.. i mean look at a 10mm wrench...



 

 

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I'm at a 23 inch tire, 225/45/15. That was only because the rivals were only made in that size, otherwise the tire is too small.

 

Add stiffer springs as suggested if your struts can handle them and you can lift the car up a bit. Right now rolling the spring up via the collar is only putting in pre-load. If you do get to the point where you have more pre-load then is weighted on the corner (lifting the car up) you basically are no longer riding on the springs.

 

150lb is also pretty soft, Gabe from TTT says his kits at the low end starts at 200F,225R. Even my tokico springs for the 280z were at 185F,200R. 

Edited by seattlejester
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Thanks guys.. Well I have new collars coming which are 6" long (I have 4" long collars now).

 

I am looking into new springs too to replace my 150#/175# setup.

 

I only removed about 1.5" from each strut so I believe my strut tube length is fine and hope the issue is due to the soft springs, short threaded collar, and small OD of the tires (23")

 

The other thing which I think is contributing is I removed the stock insulators from my setup (I am running camber plates). I ask around and everyone said I did not need to compensate for this by moving the collar perch up.In hindsight, I think I should have raised the collar 1-2" to account for the removal of the insulators. 

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I'm at a 23 inch tire, 225/45/15. That was only because the rivals were only made in that size, otherwise the tire is too small.

 

Add stiffer springs as suggested if your struts can handle them and you can lift the car up a bit. Right now rolling the spring up via the collar is only putting in pre-load. If you do get to the point where you have more pre-load then is weighted on the corner (lifting the car up) you basically are no longer riding on the springs.

 

150lb is also pretty soft, Gabe from TTT says his kits at the low end starts at 200F,225R. Even my tokico springs for the 280z were at 185F,200R. 

 

I thought the threaded collar was intended to raise and lower the car. Sounds like you are saying the collars are not designed to lift the car up by tightening things up. 

 

Thanks for clarifying this for me ;)

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The 10 " inch, 150 lb/in springs may cause you a problem as well.  The sprung weight per corner is around 600 lbs, so the springs will compress about 4 inches with the car sitting in the driveway.   When you hit a bump you will try to compress the springs an additional 2 - 4 inches.  Unfortunately, the springs will stack solid before you can get that much more travel.  

 

The free length that you need is related to the rate of the spring. The stock springs were about 100 lb/in and had a free length of about 15 inches.  When I ran my car on the street, i had 250 lb/in springs with a free length of 10 inches on the rear and 200 lb/in springs with a free length of 12 inches on the front.

 

Currently, I run 500 lb/in on the front and 400 lb/in on the rear with an 8 inch free length (no longer a street car).

 

If you want to stay with 150 lb/in springs, you should try for at least a 12 inch free length.

 

BTW,  I have my old 250 lb/in springs (2.5 diameter coil-overs) for sale cheap.

 

Thanks.. very interesting. I bought my setup off someone and I guess I know why I got a good deal  :(

 

I am looking at 225# front / 250# rear with new longer collars. I hope this will get me sitting where I need to.

 

Any idea who (what application)  would use 150#/175# springs? I would love to sell those but am not sure who would use them.

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You'll only preload the spring if the shock absorber/strut is fully extended.  Depends on your springs and spring rate and how high you lift the car.  The stock Z car strut has some preload with no weight on it, but a low rate that lets the car drop under its own weight.  There are many interactions to consider.

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The threaded collar will lower the car and raise the car, but if you are maxed out in height aka shock is fully extended and you keep cranking up on it you are just adding more preload. With a spring so soft I'm worried about coil bind potentially coming into play, my apologies if I led you astray.

 

I'm thinking more from an assembled coilover where you turn the body for height adjustment and the perch for pre-load. Given the strut insert you would actually have to jack the car up quite a bit to start engaging pre-load in the GC style coilover. 

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