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260Z suspension query - springs & shocks


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#21 Dan260Z

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Posted 01 May 2014 - 06:19 PM

FWIW, I got the following info from King springs (cut and paste from the guy's email):

KDFL-04  175lb Low 260Z Front
KDRS-09  175lb Low 260z Rear
KDFS-04  180lb Stock height 260z
KDRS-05  175lb Stock height 260z

Also - if I understand this, most people are reporting "low" springs "raise" the car?  In that case what's the point of using them? 

Man nothing is easy with an S30!  I'm literally at the stage of cleaning up and reinstalling the struts on my '74 2+2, and I have no idea whether to use 260z kings lows and full length 260z KYB's... or shorter Z31 KYB's spaced down and cut springs?  Custom Kings? ($$), some other brand of springs?

Gareth, I ended up getting a set of Z31 KYB (just GR2's) from Baz - I measured them as being only 5-7mm shorter than stock at the front - haven't tried the rear yet (possible the 30mm you mention was the rear?).

I was about to sell them and just buy 260z versions and king lows... until I read this thread... :(

#22 gilltech

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Posted 02 May 2014 - 11:17 AM

FWIW my conclusion is that the replacement springs I bought - the 'low' versions - are a little too stiff and the fronts are also physically too short.
The back end on my car is now slightly higher (10mm??) than on it's old original & 40-yr old tired springs. But acceptable, especially if they settle down a bit with use.
The front end is also slightly higher than before (15mm??) with the car sitting down on the springs. But with car raised & suspension at full droop the springs are not captured, so not acceptable; so either I find a shorter strut insert, or find softer/longer springs, or re-use my existing springs (re-tensioned perhaps).
The 'standard' versions which have the same rating would push the car even higher, so I can't see how they would be usable.
I haven't decided which way to go as yet.


#23 Dan260Z

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Posted 02 May 2014 - 11:36 AM

Let me know if you end up selling the king lows - I haven't decided yet either which way to go, but I may be able to use them as I have a set of Z31 shocks that should reduce the drop on the front by about 5-8mm (more if I take the perch off the bottom of the shock and space it down further).

Stiffer actually sounds good to me as mine will only be a weekend car - but yeah I'm still curious about the raised height.  My calcs on the standard (OEM) springs I have suggest they are the same rate as what King supply (for both lows and std), so in theory we have same rate as OEM, only shorter - should equal lower.  Perhaps the 2-seaters have lighter OEM springs given they're lighter?  (I have a 2+2)

If you're interested, ping me the Spring diameter, wire diameter, free length, and number of coils and I'll try to work out if the OEM 2-seater springs are softer than mine.

Also as a side note I measured my FRONT struts last night and they also appear to be about 290mm between the perches - so with the 280mm springs they'd also be non-captive - but perhaps using the shorter z31 shocks I can keep them captive.

#24 Dan260Z

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Posted 02 May 2014 - 11:50 AM

Or if anyone is interested in calculating it themselves:  http://www.acxesspri...calculator.html

I got around 190lb for the stock 1974 260z 2+2 Fronts, tad higher than what King advertise but I may have chosen the wrong material (or perhaps mine aren't stock?  They're dirty/black but on some chipped areas they appear to green or blue underneath.  They measured around 330-340mm long free)

#25 gilltech

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Posted 02 May 2014 - 05:06 PM

Dan260Z, FWIW my originals measure about the same length, which is down on stock according to my Nissan manual. If you have one to hand you'll see that factory spring lengths & rates varied quite a bit depending on sales market, if A/C fitted, standard or firm option, 2-seat or 2+2, etc.

If yours are blue underneath the black then either someone painted them to make them look pretty or they're aftermarket.
I suspect a lot of Zeds by now have had new firmer springs installed at back to reduce the typical acceleration 'squat'.

On mine the new rears will be fine but the lack of 'capture' on the fronts is not acceptable, & I'm not prepared to wire them in place. I think a 20mm?? shorter strut insert with suitable spacer underneath would be best but I haven't investigated the matter any further as yet.

#26 Riceburner

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Posted 02 May 2014 - 09:47 PM

Gareth, I ended up getting a set of Z31 KYB (just GR2's) from Baz - I measured them as being only 5-7mm shorter than stock at the front - haven't tried the rear yet (possible the 30mm you mention was the rear?).


:-\ Not sure what's going on there, here's the body length on mine. I would've thought the rears would be longer than fronts, I'll see If I have the part number from them.

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#27 Dan260Z

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Posted 05 May 2014 - 02:02 PM

OK so I've bit the bullet and decided to section the fronts on the weekend...  with the roughly 6mm shorter Z31 shock and by removing a further 5mm from the bottom of the shock's little perch/foot, I was able to section the strut by 12mm (with 1mm of crush on the shock to hold it in place in the gland nut inner taper).  Hopefully that allows me to keep king lows, cut stock springs, or some other spring solution captive (with the added benefit of adding some suspension travel).  Any more and I would have needed shorter shocks or to lose the shock perch/foot completely, which I preferred not to do.

Haven't measured the assembled length yet between the spring perches but will let you know once I do.


Also meant to measure the KYB Z31 GR-2's for comparison to the AGX's over the weekend but forgot - will try to do so this week.

#28 gilltech

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Posted 05 May 2014 - 06:40 PM

You seem to be making good progress Dan260Z.
But what I don't get is why these aftermarket springs are the length & rating they are. I mean, according to my Nissan manual the factory RS30 spring rates could be anywhere from 103 lb to (IIRC - manual is not to hand) about 115 lbs or so. All depending on market, standard or hard, A/C or not, 2-seat or 2+2 etc.
So why are the so-called replacement 'standard' springs up at 175 lbs, & way shorter than stock. IMO a replacement 'standard' spring should be just that, either close to or OEM. And then the 'low' option of about 30mm shorter can be a little stiffer to compensate. Either way they should fit such that the springs are fully captured.
It's all to do with the number of coils over a certain length, the diameter & the cross-section of the wire.
To me the specs of the ones I've bought are just wrong.
So I'm following your efforts with interest, as my front struts still have the original internals & I don't mind replacing them with an appropriate insert if that will solve my problem.

#29 Dan260Z

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Posted 05 May 2014 - 11:02 PM

Cheers... time will tell once I get my hands on some king lows.
I agree though.. it is very disconcerting. Even if I can keep lows captive I've no idea if they'll actually lower my car.. and it'll be years before it's all in one piece and a representative weight so I can find out. Certainly as I progress though I'll keep you posted. Would be great if someone in melb could even loan me some king lows so I could at least let you know if they fit!  And I'm still super eager to run the spring calculator over them and see what rate they really are.

The plot thickens further re the z31 shocks.. my kyb gr2/excels are 36cm... longer than Gareths kyb agx's. I have 4x kyb 365056.. supposed to be z31 fronts... perhaps Gareth has rears or a different variant of z31 (eg. turbo/non turbo?)


#30 Dan260Z

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Posted 05 May 2014 - 11:13 PM

Heres a pic.

Also I discovered the green and blue marks on my springs are just that.. dots that appear to be identifying marks (perhaps to identify them on a production line?). The rest is black through to the metal. My 2+2 had air con and I suspect was originally manual.. and is a DRS30 if that makes a difference. I don't have a manual unfortunately... mind if I ask which one you have and where to buy it?

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#31 gilltech

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Posted 06 May 2014 - 12:29 PM

Dan260Z, sounds like your springs are factory then. Yes the colour dots will be code for the assembly line. But I don't have a decoder for them like I do for my Mustang for example.
And I doubt if these aftermarket springs will lower your car, IMO they are too stiff for that as they replicate the ride height of the softer factory springs under normal load. Well, that's my finding anyway. And like me, others on here have also found that the 'low' versions don't provide spring capture.

I have a hard copy of the original Nissan manual for the 260s, must have bought it well over 25 yrs ago. I see them pop up on eBay from time to time. I've had my RS30 30 yrs later this year. It's in storage, I'm giving it a mech refurb as time permits.

Give me your email address & I'll send you my jpg scans of the spring specs pages; I tried to upload them to this post but the file sizes are too large.
I'll also pick your brains regarding the dust boots, mine have long rotted away & I should put new ones on while I'm at it.

#32 Dan260Z

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Posted 08 May 2014 - 12:44 PM

Interesting re. the colour dots.  Good to know at least that I have a factory set to reference in terms of length, etc.

In terms of whether the kings lows would lower mine - there is something I could do to get an idea - if you (or someone on here) could provide... rough measurements of

- The coil wire diameter
- Coil diameter
- No of coils (inc the squared off end coils)
- Free length

...I could calculate the rate.  Then, in theory, if the rate is similar to my stock springs, but the length is shorter, they should in theory lower my car.  As for captive, the sectioned struts should help in that respect.
I'm willing go out and buy a set of lows off ebay, etc but obviously running the spring calc over them first would help justify the purchase given your experiences.
Theoretically going by the rate King advertise (175lbs), adn the shorter length you mention (280mm??) they should lower mine, as my stock springs worked out to ~190lbs on the calculator and are around 330mm long).  Perhaps the 2+2's are a lot heavier...

That's be awesome if you could send through the scanned pages... will PM you my email address as soon as I post this :)

No probs re. the dust boots, still haven't received them but will let you know as soon as I have them.

Gareth have you any info or thoughts re. our differing Z31 shock lengths?  Wish I'd got some as short as yours now as I could have sectioned more out of the front struts and opened up my spring options a lot!






#33 fluegel

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Posted 10 May 2014 - 06:44 PM

For the record I've got KYB 361003s in the rear and 361002s in the front. The springs are what came with the car and are captive at full droop. The car is a 1976 2+2.
Richard




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