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Discussion Starter #1 (Edited)
I've been looking at various options for new shocks for my '89 non-SE. I'm well aware of the Bilstein/Eibach program as well as the GAZ/SPAX/AVO/etc. options and I'm not really looking for recommendations. There are enough threads on that subject.

My question is more fundamental. I'm just trying to understand the suspension progression over the years a little better. I'm aware of the adjustable links that were put on the rear as the wheel and tire packages became larger, as well as the spring rate and alignment changes over time. What I'm curious about is the actual suspension geometry, and cross-year interchangeability.

Depending on which shock manufacturer I'm looking at, some are specified for subsets of model years (88-93 for example) while others indicate applicability to the entire range from 88-04. And of those that specify subsets, the subset years are not the same from one manufacturer to another. What's more, when I look at the OEM front shocks installed through May of 89, the spring support platform is clearly positioned ~1-1.5 inches above the lower mount vs just above the mount for later 89 through I-don't-know-when.

So, my question is...what gives? Did the actual geometry change, and if so how? Is the change in shocks just a function of a change in spring height/weight/shape(conical vs striaght)? If the geometry did fundamentally change, why are the years specifed accross manufacturers not consistent, and if it didn't change, why don't they all specify the full 88-04 run? I would guess that some of it is due to adjustability and operational parameter ranges of the various shocks, but it's not clear to me exactly what those are, especially in light of the inconsistency I've noted.

It's probably not a simple or short answer, but if anyone can shed some light, I would really appreciate it!

Thanks!
 

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Discussion Starter #3
if you search, you will find this article: Esprit Damper Programme 2006


Lotus did an intensive research & testing with this subject (in collaboration with bilstein & eibach), i don't think any backyard mechanic here can do better what the lotus did....sooo....
As I said, I'm well aware of the program. I've read that article and others. My question is about understanding the progression, not redesigning the suspension. To reiterate what I said just above, I'M NOT LOOKING FOR RECOMMENDATIONS. I'm looking to understand what has changed.
 

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well, I wish to understand what lotus did too on their research, testing and collaboration.
They are not willing to release the technical specification due to their big investment.

I'm sure the progression will be one of them. Maybe there's a suspension engineer here that can explain.
 

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Discussion Starter #5 (Edited)
Not to belabor the point, but I didn't ask for an engineering analysis either. I'm asking how the original design progressed over the years (or stayed the same), and how interchangeable the newer pieces were with the earlier years. It's a mechanical question. Let's give it a rest, and give someone else a chance to respond.
 

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You are talking about a huge difference going all the way from '88 to '04. In '97 when the Esprit got the V-8 there were a LOT of changes to accommodate the different motor. You need to break up your question into '88 to '95 with the I4 and then '97 to '04 with the V-8. Over the years there were evolutionary improvements but the basic suspension remained very consistent.
David Teitelbaum
 

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outside of the lotus bilstein/eiback setup, is there a preferred shock/spring combo for those that are looking for a lower than stock ride height? I read a few posts that said the bilstein/eibach combo results in a slightly higher ride height.

there doesn't seem to be much info in the US. I know JAE offers a Spax setup, but I can't find any info, feedback, ride quality, handling, etc on the spax setup.

What about other offerings? any good reviews on those?
 

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I had the Spax on my 89se for many years. I liked the ride and handling and adjustability with stock springs. The only real issue was that the front ride height was a little too high. I know some people remove a spacer to get a lower height.

Now i have JRZ double adjustables, and thos can go waaaay too low if you like rubbing on everything.
 

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Discussion Starter #11
So, putting these messages together, I gather that while numerous changes were made to the suspension parameters over the years, the actual design remained proprtionally the same. Therefore, if I understand correctly, shocks and springs must be compatible, but so long as that condition is met, the assembled shock/spring unit will fit pretty much any year (and yes...I completely understand that just because it fits, doesn't mean it's the proper setup for the car :). If that's the case, then I'm interpreting the differences among the various shock option fitment specifications as having to do with how each design is compatible with the changing spring sets over the years. Do I understand or am I missing a piece?
 

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I'm not sure about the spring cups for later years, I think they might have changed... So installing later shocks on an earlier car could give some funky ride height differences...

I have some shocks that were originally made for a V8, and still required heavy mods to fit my SE. The spring rates are pretty much different than most people run on a 4 cyl (rear 350lb, front 300lb). IIRC front springs on an SE are stiffer than the rear. In the V8 I think the rear are always stiffer than the front.
 

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Hey Travis, what mods did you need to fit the V8 bits? I don't recall changing anything when I was using them. Also, where did you get the spring rate info?

FWIW, I'm currently running 300 front, 250 rear.

Dale, there were a lot of small geometry changes made over the years. Some feel your '89 non-SE has the best front geometry, and it may have been the basis for the X180R race car chassis. There were changes to the front uprights with the introduction of the SE, and further changes to the wishbones with the introduction of power steering. In general, just about everything will bolt up, but...

That said, I ran V8 wheels, tires, shocks and springs on my '90 SE for quite a few years with good results. Putting V8 wheels on a car with earlier suspension will result in a change of about 1/2" due to the larger front wheel diameter.
 

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Hey Sanj,

Well, to be clear, it's not V8 suspension that I fitted, but race suspension that was spec'd for a V8... If that is clear...

For springs, my friend Lew has 425lb/in front and 300lb/in rear.

I found this on the TE list
Rating is in lb/inch and(N/mm)

98 V8 GT: F211(37) R245(43)
Sport 300: F313(55) R342(60)
V8: F260(45) R250(44)
Sport 350: F350(61) R314(55)
SE: F171(30) R154(27)
Final V8: F327(57) R316(55)
X180R: F363 ft lbs
R337 ft lbs
Bundy X180R: F382 ft lbs
R365 ft lbs
The JRZ were a one off for a V8, and then a guy here sold the JRZ to me and the car later.

They are normal double adjustable race suspension, or you might say universal...

The main problem with fitting most shocks to the Esprit is that the window in the front lower wishbones is fairly restrictive. It is difficult to find a shock with the correct length from lower eye to cylinder body. The shock body often fouls the edge of the window in the wishbone.


My friend fitted Konis to his X180-R, but Koni doesn't make a shock with an eye length long enough, so he had a race shop do this.


My other X180-R friend has Carreras (QA1) and they hit the wishbone a bit...

you can see where the spring perch adjuster threads have been scraped off.


My old SPAX from JAE fit fine, but you could not lower the two locking rings and the spring perch low enough to get a normal 170mm ride height in the front without removing one of the rings or some of the rubber cushion.


These are the JRZ's
Rear

Front


You can see where the wishbone fouled the shock body


And the remote reservoirs with the compression damping adjustment and the nitrogen "platform" cylinder.



Have to remember though that the Lotus suspension usually has highly pre-loaded springs (especially in the front), so they may have a natural low spring rate, but they are so tightly wound when installed that it would take a much stiffer spring with little pre-load to equal that soft Lotus springs ability to hold up the car (static).

I had to put quite a bit of pre-load on my front 300's to get to a ride height that didn't rub. I think I'd rather get stiffer front springs with less pre-load.
 

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Vulcan,

couldn't you have cut half a coil off the springs when you had your old Spax setup, if you needed it a bit lower?
 

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I just installed the Lotus Bilstein/Eibach kit, and replaced all the lower arm bushings. Very expensive, $3k parts only including $600 for the bushings. At least for street use, very nice. Package is very compliant yet well controlled. To me that bit of magic is what Lotus cars are all about.

The old springs on my S4s were sagging, shocks were leaking. I used the higher of the two suspension heights on the Bilsteins as I want the most suspension travel for rebound available. A little more road clearance is a plus. The shocks come assembled in that position, so its just a bolt on deal.

I was able to to borrow the Lotus bushing installation tool. The job would have been impossible without that tool. The bushings were definitely shot even with only 12k miles on the car. Don't spend thousands of dollars on springs/shocks and not consider the bushings.
 
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