KYB 361001 ODO7 (0D07?) OEM for my '73 240z?

[DoctorMuffn]

I just pulled the rear damper out of the upright shock tube on the driver side rear. (I'm struggling with the gland nut on the passenger side assembly but I'll get it). And the part number I find on the silver KYB damper is 361001 ODO7 (but that might be 0D07). I was curious if this part by it's numbering would be the (now 40 year old) shock the car originally came with. There are a few reasons that lead me to believe these are originals:

1. I replaced the spindle pins (along with bushings and other things) back in 2009JUN and they (the pins) seemed to have never been removed.

2. The rear springs seem to be pretty original now that I have them out and can see them. If you change shocks why not change springs?

3. The gland nuts for the damper/shock tubes seemed to be untouched and I'm struggling to get the passenger side off which tells me it could be bound up by 40 years of corrosion...

Other questions:

I've been reading through a lot of posts by Arne, jmortensen, Carl Beck, Marty, KTM, beandip, wa5ngp, ZSaint, Pop's Z, bpilati, and many many more in myriad suspension threads to lead me to the following lot of questions:

How can I get my hands on Euro Spec Stage 1 springs?

Are the Euro Specs progressive or linear?

I'm lead to believe the Eibachs are progressive. True?

I'm lead to believe that Koni replacements (86-1811 and 86-1812) are hydraulic units (as in not gas-filled dampers) and because of this won't be inclined to raise my ride height from stock when paired with Euro Spec Stage 1 springs. True?

Are the KYB G2s (36-1002 and 36-1003) gas-filled dampers?

Will the KYB G2s raise my ride height above stock when paired with Euro Spec Stage 1 springs?

More background and intention with my build. I pulled my KYB damper out of the driver side rear and compressed the working piston by pressing in the damper rod. It doesn't rebound back up. This leads me to believe it's not functioning properly. It takes a lot of force and time to draw it back out to full length. If it's gas wouldn't it rebound automatically? Do hydraulic dampers not rebound on their own?

I've also been leaning toward the Tokico TOILK252 (white kit with adjustability) since it's a kit of springs and shocks together. However, I've been reading a lot of unsettling comments on how excessively stiff they are. Maybe since I'm not running my sway bars and have wider wheels (acting at a greater advantage to the springs) this effect may be countered a bit. I also like the idea of the ride height being about 1" lower than stock much more than the possibility of higher than stock heights when the Euro Springs are mated to different shocks; I understand this is a gas shock tendency to add to the spring rate and in turn raise the ride height.

If I don't go with the Tokicos then I'd like to garner a supple yet responsive ride with Euro Springs (if they're linear) over the Konis or KYBs without raising my ride above stock. Those are the few options I've come to be considering now given my research over the last month.

I guess I'm looking for linear springs and shocks that work together well to give a supple ride when on the street commuting but a sporty responsive ride while driving the twisties. And I'm not using the sway bars so as to keep my suspension as independent as possible at each corner per Fred Puhn's How to Make Your Car Handle. Or maybe I read that in Bilinski's Kimini.

Thanks in advance,

Sean

[Arne]

I was curious if this part by it's numbering would be the (now 40 year old) shock the car originally came with.

No. Originals were not sealed cartridges. They were damper rods in tubes, and the entire strut tube was filled with oil. FWIW, rear struts can easily be changed w/o removing the spindle pins. I always did mine that way.

How can I get my hands on Euro Spec Stage 1 springs?

You'll need to find someone who has a set they aren't using. I know that several people bought more than one set when they were available.

Are the Euro Specs progressive or linear?

Linear.

I'm lead to believe the Eibachs are progressive. True?

Yes.

I'm lead to believe that Koni replacements (86-1811 and 86-1812) are hydraulic units (as in not gas-filled dampers) and because of this won't be inclined to raise my ride height from stock when paired with Euro Spec Stage 1 springs. True?

True.

Are the KYB G2s (36-1002 and 36-1003) gas-filled dampers?

Yes.

Will the KYB G2s raise my ride height above stock when paired with Euro Spec Stage 1 springs?

Yes. They raised my car approx 15mm (5/8").

[DoctorMuffn]

Thanks, Arne, those direct responses to my questions were very helpful. It seems since the Euro Specs aren't readily available I'll just be going with the Tokicos and expecting a slightly less rigid ride than others have experienced due to my set up. Thanks again. And what promptness. Have a great Sunday.

Oh! One thing then... I won't be needing oil in the tubes when I replace the inserts (dampers shocks whatever) with a sealed cartridge like the KYBs I pulled out or the Tokicos I'm considering right? I've heard things about oil being poured into the tube to help any damper with heat transfer to the tube itself. But what you say makes it sound like the tube was the original "cartridge" with a working piston closed up within it and the enclosed oil serving as the dampening fluid and not intended primarily for heat transfer. Could you speak to these conclusions I've been led to?

[Carl Beck]

Sean - I have an NOS set of Euro Specs $425 plus shipping - As I recall - Arne recommended 1 1/2 to 2 coils be cut off the Euro Spec's when used with non-gas pressure shocks to get close to the original ride height.

FWIW,

Carl B.

Edited February 24, 2013 by Carl Beck

[Arne]

You're pretty much correct on the oil issue. It is not necessary for the new cartridges. But it doesn't harm anything either. You don't need much if you use it, maybe a couple of teaspoons or so.

[DoctorMuffn]

Awesome, Arne. Thanks for that. Whatever I go with I'll use some oil to cool the cartridge.

And I appreciate the offer, Carl. Let me say that some of your clarifications in other threads were incredibly helpful. I'm going to do some price comparisons and I'll pm you with some questions if that's alright. And regarding what you said with cutting 1 1/2 to 2 coils off of those springs when paired with non-gas dampers (such as Konis for example) to bring it to stock ride height is contrary to the answer Arne gave in my question specifically about that pairing. Now I'm not sure what the case is, but I'll go back to a couple threads to cross reference what he had said before. It just bothers me to envision myself cutting a perfectly new and good set of springs. Then again maybe it's not such a big deal.

The responses to this thread have been very much appreciated. Thank you both.

[Carl Beck]

Hi Sean:

Cutting 1 1/2 to 2 coils off the Euro Spec.'s will slightly increase their spring rate, but that is not a problem. Just use a hacksaw - not a torch as you don't want to heat them.

Reviewing Arne's E-Mail report from Feb 10, 2007, he reported cutting 1 1/2 coils off the front and 1 1/4 off the rear - to get the car back close to original ride height. Even then it was still sitting 1/8" higher in front and 1/4" higher in the rear. He was going to drive it that way to see if things settled down a bit more ... That pretty much matched the experience my son and I had when we put them on my son's Z.

FWIW,

Carl B.

[Arne]

Carl is correct, the Euros need cut down for any insert type in US strut housings. As noted above for non-gas, and about another 1/2 coil each to gas charged. I used them with both, and posted in bits and spurts, and so picking info from my comments can be hard to follow at times, depending on when I posted and how far along the trail to the final config I was at the time. Here's the summary of the various ways I tried mine:

Euro springs with US-spec strut housings.

• Un-cut with non-gas inserts - Raised car about 3/4" to maybe 1" over factory stock spec

• Cut 1.5 coils F, 1.25 R with non-gas (NOS Mulholland) - Raised car 1/8" F, 1/4" R over factory stock spec

• Cut 1.5 F, 1.25 R with gas (KYB GR-2) - Raised car 3/4" F, 7/8" R over factory stock spec

• Cut 2 F, 1.75 R with gas (KYB GR-2) - Car sat at factory spec both ends (± 1/4" or so)

For reference, un-cut, un-sagged stock US springs:

• With non-gas (NOS Mulholland) - stock height

• With gas (KYB GR-2) - Raised car about 5/8" both front and rear

Recommendation: If you plan to cut springs, go conservative, and take good notes. It's better to need to cut another 1/4 coil than to have gone too far. I had mine out and trimmed them several times before I got what I wanted (or could live with). Hack saw works, but I used carbide cutoff wheels on a small hand-held Dremel. Much quicker, but still minimal heat build-up.

[DoctorMuffn]

You were right, Carl. I went and found some of Arne's posts from before and he did say the ride height was raised from USA stock height with those Euro springs. And now he's confirmed it with his notes just above.

Thanks to you both again for the references and copius notes. Even though the Euros and shocks purchased separately and paired up will run me quite a bit more than the Tokico ILK252 kit I'll be considering it. I'm also waiting to hear back about whether the springs on the Tokicos are linear or progressive. I was really leaning toward linears which the Euros are. Hmmm... Thank goodness I have some time (about a week or two) before I make this decision. In the meantime I'll be finishing the rebuild on my transmission; it seems like I got caught up in that "while I'm at it" thinking when I pulled the trans to rebuild it and replace the clutch and flywheel - I went after the rear suspension too. No worries since I did the pins a while back. I'll have to try the damper replacement without pulling the upright next time. Although, I was fortunate enough to get a stand up spring compressor on the cheap when my brother closed his shop a while back so that might not be useable if I don't pull the upright out.

Decisions. Fun ones.

Why is it that cutting a spring will raise its rate?

[LeonV]

Why is it that cutting a spring will raise its rate?

Physics!

A coil spring is just a wound-up wire of metal. When a coil spring compresses, what actually happens is the metal wire twists in torsion, i.e. deforms in order to compress the spring. When you cut material out of the spring, you are shortening that metal wire. A shorter wire is harder to twist, thus the spring rate increases.

It's akin to taking, say, a plastic ruler in your hands and twisting it. If you make that ruler shorter (put your hands closer together) it will be harder to twist.

The analog to this in bending: take a long metal rod and a short one, holding all else constant. Which one will be easier to bend? Same idea.

Edited February 26, 2013 by LeonV

[DoctorMuffn]

Got it! Excellent explanation. Finally it makes perfect sense. Thanks, LeonV.

[LeonV]

Not a problem.