Front coilover conversion question

Suspension, including wheel, tire and brake.
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obrut
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Joined: 15 Mar 2016 18:06
Location: Lemont, IL

Front coilover conversion question

Post by obrut » 01 Feb 2018 08:13

I'm almost ready to swap the 280zx struts onto my 72 510. There is a post on ratsun selling eibach springs and carrera sleeves for $90. He has 8" long 200 pound springs which I think would be perfect for my setup. Any reason I shouldn't get these? $103 shipped sounds pretty good. What else will I need to run these?
1972 4 door hopefully with a L20B and side drafts before to long

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Byron510
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Re: Front coilover conversion question

Post by Byron510 » 01 Feb 2018 10:38

The price does sound good, but the spring rates may not work for such a short strut arrangement on a low street car. It will depend on your ride height, how you drive and what you drive over. It'll ride good, but may bottom out easily. If it does bottom out, it'll smash the valving out of the bottom of your inserts in short order and destroy them. You also stree everything else on the car and this can lead to broken suspension components with disastrous results.

I guess the first question to ask is what ride height do you plan to run? Then you need to ask what length of inserts you plan to run.

I can tell you that I have run 200 lbs springs on wagon length inserts on a rally suspension application where there was significant wheel travel available and really good shocks - and it worked well - with 10" and 12" length springs.

But you have to remember that the wagon insert was 2 1/2" longer than a stock ZX insert.

To add to this, a very popular front insert to run today on our 510's is the gen1 MR2 insert (front or rear are within 1/2" of each other). Both are nearly 2" shorter than a stock ZX insert. You can see where this is going in regard to available wheel travel. The less wheel travel you have, the stiffer the spring needs to be to prevent bottoming out. Preventing bottoming out saves your inserts first, but also is much less stressful on the rest of your suspension package.

Advice - well it's each to his own, but I have found that with a good quality insert like a Tokico Ilumina adjustable that I was able to control 250-300 lbs springs utilizing Gen1 MR2 inserts in shortened ZX struts and it works well for a low street ride height on 15" wheels which gives about 2 1/2" droop and compression. On 13" wheels, I'd be using the stock length ZX struts with the same quality inserts, but you'd be technically raising your ride height (more gap in the wheel well) to get the same ground clearance as the 15 set up above.

You could try the 200 lb springs to start with on your set up, but be prepared to upgrade to stiffer springs if you're going low.

To confirm what you're looking at - are they 2/12" ID springs? This is important because they are the most available size. There are 2 1/4" ones out there, but they won't fit over the struts with a threaded sleeve on there.

Other information you may need while engineering your set up - The strut tube diameter on a 510 and ZX is 51mm which is within a hair of 2" dia. The 510/ZX internal strut nut thread is M48X1.5mm. Most aftermarket threaded collars have a 2 1/16" ID for use with 2 1/2" ID springs. This collar size worked well on a 510/ZX strut with a thin shim to keep them in place. I've heard some simply use electrical tape! I use brass shim stock.

Beware when dealing in used stuff: Now there is a bunch of metric sized stuff out there for specific applications that further confuses things, and a crap load of Chinese made odd ball stuff that just can't be counted on - the Chinese have not got a grasp on quality steel production, and when it counts like it does on a spring or harder materials, they just are not there yet on the quality side. So you have to know what you've got when going 'used' to make sure your package all works in the end. A good quality spring will have the rating painted right on them (like Eibach does), so you should know what you're looking at. If it's not marked - walk away unless it's truly free - because you won't know where your starting from.

Hope this all helps and isn't too much information overload! Keep us posted.

Byron
Love people and use things,
because the opposite never works.

obrut
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Joined: 15 Mar 2016 18:06
Location: Lemont, IL

Re: Front coilover conversion question

Post by obrut » 01 Feb 2018 11:19

I want the car just a little lower then stock and I'll be running 15x7 panasport wheels that it came with. I was thinking about pulling the stock front struts and keeping them intact. So I started looking at coil overs for the 280zx struts I already have, I haven't decided on the front inserts. I was looking at just running KYB excel stock length 280zx inserts in the 280zx struts and then just KYB 510 rear shocks with stock springs for now.

I$90 didn't seem bad for sleeves and springs, he also has 10" 150 pound springs and sleeves for the same price.
1972 4 door hopefully with a L20B and side drafts before to long

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RMS
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Re: Front coilover conversion question

Post by RMS » 01 Feb 2018 13:00

keep in mind that if the stock "bump height" is lowered you will need to relocate your sway bar or risk a collision between tc rod and sway bar.
if your 280 struts have the stock oil filled inserts the extended height is easily set and 30w shock oil works well with a 200lb spring. some dodge d50 front springs in the rear and some nissan sentra fastback rear springs in the front is a great combo for a street car with stock spring perches and it lowers the ride a 1/2in
two_68_510s wrote:I guess our donkeys are quicker then your sled dogs!

obrut
Posts: 45
Joined: 15 Mar 2016 18:06
Location: Lemont, IL

Re: Front coilover conversion question

Post by obrut » 01 Feb 2018 13:16

Unfortunately the 280zx struts came with inserts otherwise i would have just changed the oil.

Ill have to check the rear springs because the rear already seems lower than stock. I dont know if they are cut stockers or different. Ill have to pull one and see if there are any part numbers in them.

What do you recommend for an insert with the sentra springs?

Should i pass on the coil overs and sleeves?
1972 4 door hopefully with a L20B and side drafts before to long

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RMS
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Re: Front coilover conversion question

Post by RMS » 01 Feb 2018 13:22

its your cash and your choice.

the three cars I have installed sentra springs on all had oil filled inserts with 20w/25w the sentra spring is 123lb/in sedan 133? fastback.

a bit of info :
jason wrote:Hi Mario, here's a list provided to me by Chris Saulnier from the Bluebirds List, it's a bunch of donors providing springs that you could use with stock struts and perches.

Springs For 510 Stock Front Struts
For your swapping pleasure I have created a list of several different front springs that can be used on the 510. All of the springs listed will increase spring rate, will need to be cut to lower your car, and are commonly available in the JY. Also included is the formula from Fred Pruhn's book "How to make your car handle" (thanks Jason) that describes how to calculate spring rate as you cut. Listed dimensions for the diameter of the springs are taken from the center of the wire, not the OD or ID, this will make it easier to use the spring rate calculation. The data all came from the NAPA spring book, so things like free height and load height are approximate. The stock Datsun spring info was taken from a factory manual (thanks Jason), and can be used as a rough guide. All dimensions are in inches. It is best to measure your 510 springs both loaded and free to determine your specific baseline before trying to calculate rate and ride height changes. All of the approximate load heights are based on 525lbs on the spring.
Spring Rate Formula:
K= (12,000,000*W^4) / (8*N*D^3)
The 12,000,000 and 8 are constants.
W= diameter of the spring in inches. (W is raised to the fourth power in
the formula)
N= number of active coils in the spring. (free coils plus 1/2 coil under
load)
D= diameter of the coil, measured from the center of the wire to the
center of the wire. (D is raised to the third power in the formula)
Stock Datsun:
Spring Diameter - 5.11
Wire Diameter - .472
Load Rating - 89lb/in
Free Height - 14.25 (approx)
Load Height - 8.35 (approx)
NAPA P/N 277-3187 ($52/pair new)
Spring Diameter - 5.04
Wire Diameter - .485
Load Rating - 123lb/in
Free Height - 12.75 (approx)
Load Height - 8.50 (approx)
Application - '88-'92 Nissan Sentra (rear)
NAPA P/N 277-3180 ($59/pair new)
Spring Diameter - 5.27
Wire Diameter - .500
Load Rating - 128lb/in
Free Height - 13.58 (approx)
Load Height - 9.48 (approx)
Applications - '86-'89 Hyundai Excel w/AC, '87-'88 Mitsubishi Precis
w/AC, '79-'82 Plymouth Champ w/AC, '80-'84 Dodge Colt w/AC

NAPA P/N 277-3185 ($59/pair new)
Spring Diameter - 5.22
Wire Diameter - .500
Load Rating - 137lb/in
Free Height - 12.98 (approx)
Load Height - 9.15 (approx)
Applications - '86-'89 Hyundai Excel no/AC, '90 Hyundai Excel w/AC,
'87-'88 Mitsubishi Precis no/AC, '79-'82 Plymouth Champ no/AC,
'80-'84 Dodge Colt no/AC
NAPA P/N 277-3130 ($82/pair new)
Spring Diameter - 4.98
Wire Diameter - .500
Load Rating - 137lb/in
Free Height - 12.43 (approx)
Load Height - 8.60 (approx)
Application - '76-'78 Honda Accord
NAPA P/N 277-3129 ($82/pair new)
Spring Diameter - 4.98
Wire Diameter - .500
Load Rating - 148lb/in
Free Height - 13.00 (approx)
Load Height - 9.45 (approx)
Applications - '80 Honda Accord w/AC, '81 Honda Accord LX w/AC
NAPA P/N 277-3128 ($82/pair new)
Spring Diameter - 4.98
Wire Diameter - .500
Load Rating - 148lb/in
Free Height - 12.31 (approx)
Load Height - 8.76 (approx)
Applications - '79 Honda Accord, '80 Honda Accord no/AC, '81 Honda
Accord - all except LX w/AC
NAPA P/N 277-5187 ($93/pair new)
Spring Diameter - 5.06
Wire Diameter - .562
Load Rating - 158lb/in
Free Height - 14.37 (approx)
Load Height - 9.00 (approx) - measured after cutting off pigtail end
Applications - '80-'85 Olds Toronado (rear), '79-'85 Cadillac Eldorado
(rear), '79-'85 Buick Riviera (rear)
Notes - These have a "pigtail" end on one end that must be cut off.
They are real easy to get off at the JY, bring a long crowbar and you
can pry them off the lower mount, removing them with next to no effort.
Be Careful!!! - Don't try to "help them" by hand if they get hung up.


NAPA P/N 277-5308 ($96/pair new)
Spring Diameter - 5.26
Wire Diameter - .531
Load Rating - 131lb/in
Free Height - 15.60 (approx)
Load Height - 11.60 (approx)
Application - '83-'85 Toyota Celica IRS (rear)
Notes - These are also easy to get off at the JY, remove the lower shock
mount then pry them off the lower mount, removing them with next to no
effort. Be Careful!!! - Don't try to "help them" by hand if they get
hung up.
NAPA P/N 277-5310 ($109/pair new)
Spring Diameter - 5.02
Wire Diameter - .500
Load Rating - 108lb/in
Free Height - 14.50 (approx)
Load Height - 9.63 (approx)
Application - '83-'85 Toyota Celica solid rear axel (rear)
NAPA P/N 277-5277 ($74/pair new)
Spring Diameter - 5.08
Wire Diameter - .500
Load Rating - 115lb/in
Free Height - 14.12 (approx)
Load Height - 9.55 (approx)
Applications - '84-'87 Toyota Corolla, '85-'88 Chevy Nova
NAPA P/N 277-5174 ($87/pair new)
Spring Diameter - 4.97
Wire Diameter - .500
Load Rating - 106lb/in
Free Height - 13.05 (approx)
Load Height - 8.10 (approx)
Applications - '75-'79 VW Rabbit/Scirocco no/AC
NAPA P/N 277-5146 ($87/pair new)
Spring Diameter - 4.99
Wire Diameter - .500
Load Rating - 112lb/in
Free Height - 13.62 (approx)
Load Height - 8.93 (approx)
Applications - '77-'79 VW Rabbit/Scirocco w/AC
NAPA P/N 277-5374 ($82/pair new)
Spring Diameter - 4.98
Wire Diameter - .500
Load Rating - 113lb/in
Free Height - 13.55 (approx)
Load Height - 8.90 (approx)
Applications - '91-'94 Ford Escort (rear) - except GT, except wagon,
'91-'94 Mazda Protege (rear)
NAPA P/N 277-5376 ($82/pair new)
Spring Diameter - 4.98
Wire Diameter - .500
Load Rating - 113lb/in
Free Height - 13.95 (approx)
Load Height - 9.30 (approx)
Applications - '91-'94 Ford Escort Wagon (rear)

Later-
Chris of Maine "springing forth with useful info"

Hope it helps.
two_68_510s wrote:I guess our donkeys are quicker then your sled dogs!

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