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Spring selection for stock perches (+ Z idea )


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I'm going cheap on my 510 wagon's front suspension. I grabbed some 280ZX front struts and 2" split collars. I was going to retain the stock 510 perches, but wasn't finding many available springs for those. (Are there? I'm in the east, and '70s Datsuns aren't common in the yards)  I doesn't seem like I can get 2.5-3" drop on a stock, cut coil.

 

I want to DD the car in the summer, and need it to be able to take me everywhere, including miles of dirt roads, so super stiff is not what I'm after, but I would like to tighten it up a bit. Yesterday, while looking at an acquaintance's Datsun stash, I started wondering about Z parts...

 

What about 240/260/280 spring perches, springs (cut, if needed), and top hats/thrust assemblies on the ZX struts with my split collars? I'm not 100% sure, but it looks like the stock springs are 140lb and a bit smaller in diameter. It also seems like the aftermarket support for Z springs is better.

 

Has anybody tried this? Is there a reason why the upper spring hat assy wouldn't fit the 510 mounts? Anything else I'm not considering?

 

Thanks.

 

 

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Do you have your 510 front springs? Use them. They will fit your perches because they came with them. Stock 510 spring rate is 89 pounds/inch. (lb/in) I can work out easily enough how much spring to cut to get 140 or what ever you like. The split collars are for setting the height. On my 710 it was just over one coil. On the 510 you would have to do some measuring for me. Christ, don't buy springs just trim yours and rattle can paint them to fool everyone.

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I guess I'll begin with the stock 510 springs, like you suggest. My concern was that I'd be stressing a tired, old part by asking fewer coils to handle higher stress. I'm not worried about how it looks, I just want options and availability, which isn't the best on OE parts here in the east.

 

I may get one side pulled apart, today, and can measure the coil.

 

Thanks.

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I need to know the number of 'free' coils. That's the number of coils not touching each other and free to compress or move. The wire thickness and the coil diameter? (side to side is fine as long as you specify) I have this but need it confirmed. From this information the number of coils needed to be removed can be worked out to get the new spring rate can be easily calculated. Probably a little over one.

 

Have you given any thought to the new spring rate? or stiffness that you want? I increased my 710 about 50% and it has a nice firm ride compared to the old soft one. Many 510 owners like over 200 lb/in and if racing 300 lb/in but this is way to much for a daily driver. If way up into the 200s I would buy springs for that but if you want a judicious spring rate increase then the stock spring is fine.

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I'll grab all that info.  I was guessing 150lb, but have no idea when the mismatch between the stiffer front and stock leaf springs would become a problem.

 

My experience is with sedans and I haven't even driven this wagon yet, so I don't have much to go on. I'll be running an old Datsun Comp front bar and am more interested in roll resistance than spring stiffness.

 

I haven't figured out what inserts to use for the ZX struts, either. I was wondering if stock, open bath 510 internals would swap into the ZX parts, for now. I like your idea of running fork oil in those.

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Just remember once cut you can't put it back. 150 is perfect and you can get used to driving it firmer and lower and increase it later if you choose. Everyone is different and has different 'comfort' levels. The goon rear springs are easy to lower with blocks and while doing this you can add an extra leaf to stiffen them, this is what I did on my 710 goon.

 

For zx struts the longer 510 internal oil dampers won't fit. If the zx strut still has it's original dampers then all you need do is change the oil to something thicker or replace with zx inserts or a shorter insert. If running shorter inserts you will need to stack washers in the bottom of the strut tube to support it.

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18687614102_c3bb46a45b_z.jpg[/url]

 

The coil is 12mm thick. (.47")

 

O.D. of the coil142mm (5.6")

 

I.D. of the coli is 118mm (4.7")  Centerline of the coil is 130mm)

 

I include the pic so that you can tell me exactly how many free coils I do have. A small amount of movement would bring additional coil onto bind, so after you  specify, I'll know how it's measured.

 

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Looks like 6 coils and a fraction and your numbers almost agree with mine. This works out to 84 lb/in (close enough)

 

 

Well I get about two and a half coils removed as producing 144 lb/in... that's no good it makes the spring much too short (I think) even with split collars. My 710 springs were 0.5" thick, 6.5 coils and the diameter was 5"  Thicker wire an smaller diameter makes for a stiffer spring. I guess the 510 spring is just softer to begin with so more has to be removed. Maybe too much. I think it best you order springs.

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I forgot to mention that total length is 380mm or 15".

 

Who still makes stock-sized springs? I've looked and haven't found much.

 

Thanks for doing that work, Mike.

 

Edit: Stock 240/260/280 spring perches work perfectly with other Datsun 2" O.D. struts. The upper thrust bearing is the same, so you can retain the original 3-bolt upper strut-to-chassis mount, your strut top bearing, and then use the Z-car upper spring seat, Z spring, and lower Z spring seat on your strut (using a split collar to adjust height..

 

What does this gain you? Not a tremendous amount, but the Z springs are stiffer to begin with and can be cut to increase their rate. Also, the aftermarket for Z coils has to be better than that for stock-sized 510 coils.

 

I'll post pics when it's together.

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Small update:

 

I scored some 260 front spring perches and springs, F&R, for the cost of 2 locally-brewed 6-packs.

 

If my calculations are correct, I get 114lb front or 136lb rear, prior to any cutting. These should be right in the ballpark.

 

My basic Excel-G/GR2 280ZX struts arrived today. I figure the added weight of the ZX should mean slightly sporty damping for the 510.

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I installed the rear Z springs with the Z perches, on the ZX struts. The Z  struts are 2 1/8 or 2 1/4 Dia, so the perches can move off-center, slightly. Not likely to be a big problem, but check tire clearance in a worst-case scenario or figure out a way to keep them centered. In order to get the proper ride height, I had to reduce the preload to about zero.

 

I can't tell much by pushing up and down on the car, but the cheap ZX struts and Z rear springs (slightly stiffer than Z fronts) seems to be a reasonably firmer set-up. I won't know if the lack of preload harms the spring ramp-up or how the components work together until driving it, but fingers are crossed.

 

This is lowered approx 2.5 inches front, 2" rear from where it was.

 

18687924850_f3ee766dc6_z.jpg

18875596935_56ee18cf8b_z.jpg

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Good info here, thanks for getting back to us with the result. Tell us how she feels after a test drive.

 

Just to be sure I understood this clearly, you are running 280zx strut inserts with 260z rear springs installed on them, all on the original 510 strut/knuckle? And lowered perches on the pipe clamps?

 

Wagon looks nice. Nice work

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It's 280zx struts and cheap whatever-they-call-GR2-inserts these days.

280ZX calipers and 13/16" (Z) M/C

stock wagon steering arms and lower ball joint

260Z rear springs, uncut

260Z spring perches (240Z would be better)

Split collars for the lower perches.

510 strut top bearing and rubber bushing/mount.

 

Let me know if anything in there is unsafe. (;

 

I added some 20mm RCAs, today, and I learned that the later Zs, 260-280, I guess, had the larger diameter strut tubes. I measured some from a 240 and they're the same 2" O.D. as the 510 and ZX. I could have eliminated the loose perch situation if I had known that. The upper perches are the same between Z models.

 

I'm also running what I believe to be an old Datsun Comp front sway bar. I still need to figure out what to do for the rear shocks and possibly a rear bar.

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