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Looking to find out the factory spring rates for the suspension, also spring lengths.

"The 'Stock' V8 spring rates are Front 250 & Rear 275. The New Springs will be to the same specification for that model. The increased rates of the Sport 350 will be retained for that model (Front 350 & Rear 330). The Final Edition Suspension Package remains unchanged. "

Found this information if anyone else was interested.

Edited by 97-Esprit V8
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  • 2 weeks later...

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Looking to find out the factory spring rates for the suspension, also spring lengths.

"The 'Stock' V8 spring rates are Front 250 & Rear 275. The New Springs will be to the same specification for that model. The increased rates of the Sport 350 will be retained for that model (Front 350 & Rear 330). The Final Edition Suspension Package remains unchanged. "

Found this information if anyone else was interested.

Very cool getting those figures from the factory :devil:

They tie in pretty well with Mark Pfeffer's rates he posted on turbosesprit a few years back:

-------

Here's what I've compiled:

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

---------

I've fitted Marcus' full race suspension to mine, (it's my only car but I spend more time at track days or travelling to and from the track than the rest put together). Now Marcus' website recommends race is 70N/mm front and 80N/mm rear (approx 33% stiffer than S300/S350, and almost double the stock V8).

But the problem was, on the track it oversteered like a bugger. However, Marcus was sensible in matching the springs with the dampers in that they're interchangeable with the same diameter and length. So I swapped the fronts to rears. Now 80N/mm front and 70N/mm rear. I've only done one track day at Bedford since, in the streaming rain but it seems to be a vast improvement.

Previously *any* rain would have send me unrecoverably sideways. That day though, I had no problems in the bends - the big problem was on a straight line. Apart from aquaplaning at 140mph and wheelspin in fouth, the brakes were hopeless - ABS cutting in at 100mph. Ironic thing is what caught me out was not taking the corners fast enough but panicking when the ABS was working overtime through standing water. I just became paranoid (no way can I turn in at this speed...) and staying on the ABS twittering brakes well into the turn in. Needless to say - with the weight tranfer to the front the back came round a couple of times...

So anyway my real question, the stock Esprits tend to go for stiffer rear springs but the 'sporty' versions do the opposite. The chassis is (roughly) the same so I'm curious as to how this works out. I'm also too aware that the Esprit chassis with it's backbone chassis is a bit of a liability when I'm running these extreme spring rates.

Thoughts gentlemen?

Thanks,

Neal

Edited by neal

May: DON'T hit it with a hammer!

Clarkson: Why?

May: Cause it's the tool of a pikey.

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Guest Troy Halliday

Lotus is one of the best ride and handling companies in the world. Why deviate from what they have done. I realise that you are after a more track focused suspension but have you thought of asking the factory for a bit of advice. If there was a call for an all out track focused suspension I am sure we could speek to them regarding this. As they have recently undergone some major suspension developments on the Esprit some data may be there already. I could possibly speek to them next week when I go up there to visit them.

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that discussion reminds me on a documentary/test in "sport-auto" 9/99 . With the Sport350 against a F355 .

The Lotus had won this test (even impressive for an german based and Ferrari friendly magazin...) , but one thing mentioned was the "weakness" and the inclination sideways of the Lotus .

As seen in the first post there is a much higher spring-rate in the sport350 as in the basic V8GT one. So that shows me why my car was so soft like a ocean trawler in cornering at Hockenheim easter race.

The backbone can be a problem with the body mounts an all that stuff in connection with suspension stiffness, but: As Lotus has developed a spring upgrade, is there any roll bar upgrade incoming !?

It's totally clear that the chassis system of the Esprit does not allow an rear anti-roll bar , but even the front version is a point to think about... .

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to name the things if I see them, that's what I call integrity..

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an other comment in the anti-roll bar thing: does anyone know how the mentioned (in Autocar /August '95) rear anti-roll bar in the S4 and GT2-Racecars [x180 or what ever the name was... !? ] was designed ? Would be interesting to know how the mounting points and the dimensions was calculated.

*********************************************************************

to name the things if I see them, that's what I call integrity..

*********************************************************************

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So anyway my real question, the stock Esprits tend to go for stiffer rear springs but the 'sporty' versions do the opposite. The chassis is (roughly) the same so I'm curious as to how this works out. I'm also too aware that the Esprit chassis with it's backbone chassis is a bit of a liability when I'm running these extreme spring rates.

Thoughts gentlemen?

Thanks,

Neal

I think the quick answer is the stock cars are set up to understeer which is considered safer for the majority of drivers, hence the softer front springs.

The biggest liability when running on the track and using higher spring rates are the bushes - the trailing arm pivot bush in particular gets forced around in all sorts of directions and gives the impression that the chassis is flexing etc. A rose jointed arrangement erradicates this sensation and is no where near as noisey/ uncomfortable as a lot of people would lead you to believe! - How suitable this is for road use depends on the individual....

I know that the Zanardi car (4 cyl) was running with 500lbs front and 350lbs rear when it was running in the US years ago, again all the suspension was rose jointed which included the front pivot for the trailing arm. I'm running with stiffer springs than this atm and i have some even stiffer ones to try as soon as it's warm and dry enough to get to the track.....

My Europa uses 475lbs front and 350lbs rear, the car weighs 640kgs. Driving it on a normal road rattles your eyeballs around in your head (it never gets driven on the road!) but on the track it feels quite normal and it's still possible to hit the bump stops. It should really have 600's and 450's.

The rear anti-roll bars are quite simple - they aren't too different from the one you can see on this group 5 racerpost-281-1199297853_thumb.jpg

For the road you'd be hard pushed to better what Lotus has spent years refining. For the track it depends on many different factors such as car, tyres, suspension etc and DRIVER! - Unfortunately something a phone call can't generate a definitive answer to.....

Jon

Edited by V8Esprit73
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I would agree that the factory rubber bushings need to be replaced, when I installed a monster engine in my E36 BMW I installed rear trailing arm mounts that were spherical bearings (rose joint as you call it I believe). This was essential to ensuring the wheels did not toe in and out under hard acceleration and cornering. I did not find them to be harsh or noisy on the street. I was looking to fabricate a set for the esprit as I don't think the polyurethane one will be worth installing. (Any one have experience with the polyurethane ones have any comments?)

I've removed the transmission mounts to fabricate some polyurethane replacement units, building a jig assembly and will try pour a few sets in different durometer stiffnesses. Will also do the same to the engine mounts, mine appear to be shot with age and I do dislike the rocking and rolling on and off the gas and when shifting.

Finding the compromise spring rate/shock valving for street and track is always a challenge. Springs are cheap and easy to change, so I will experiment until happy with the handling. I'll have a vast range of compression/rebound rates to play with as well.

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But that's what I don't get - increasing the front rates or decreasing the rear rates promotes understeer. Likewise increasing the front anti roll bar promotes understeer. So by that logic the S350 should understeer more than the stock car (the huge wing aside - but thats only going to matter if you're going over say 100mph).

That's why I was wondering if it was something to the with the chassis with its rigidity of a banana that starts doing strange things with high springs rates :ermm:

But maybe it's simply that for serious track use the stock car was found to be too tail happy?

P.S. I do have the S350 ARB and PU bushes all round

Off to Silverstone on Saturday so hopefully the weather will hold and I can get some useful results (still need to set all the dampers, camber, caster, etc)

Edited by neal

May: DON'T hit it with a hammer!

Clarkson: Why?

May: Cause it's the tool of a pikey.

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  • 2 weeks later...
But that's what I don't get - increasing the front rates or decreasing the rear rates promotes understeer. Likewise increasing the front anti roll bar promotes understeer. So by that logic the S350 should understeer more than the stock car (the huge wing aside - but thats only going to matter if you're going over say 100mph).

Neal, that's exactly right but ONLY EVER when looking at it from the viewpoint of an already perfectly neutrally balanced car if you see what I mean.

The fact that the front end has an ARB and the rear doesn't means that the front is likely to be stiffer in 'roll' anyway. The gains derived from stiffening the front springs would suggest that the front on most road Esprits is further from neutral than the rear and for exactly the reasons Jon stated above - 'safer' understeer.

There's also the questions of leverage and of rising/falling rate on the dampers/springs too in as much as say a 400lb/in rear spring may not actually be as effectively stiff as a 400lb/in front. So it can't really ever be a simple comparison of just the given spring rates, only spring rate effects. Which again is like Jon said and is subjective to each drivers style........which is where the trouble starts.

Oh was that my first post?!.....apologies for the rambling.......and years of lurking.

Steven

Edited by azrael
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So ....does have anyone now a chassis drawing [pdf,jpg-file] from the front and rear of the X180 and S4 race cars ??? Would be interesting to see the Lotus works-layout.

Jon has given an possible example , but I'm still in need of an original picture

*********************************************************************

to name the things if I see them, that's what I call integrity..

*********************************************************************

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  • 4 months later...

Been meaning to post an update to my build, I've included some pictures of my new aluminum double adjustable suspension. I couldn't manage to invert the shocks, would have been a pain to mount.

post-1829-1211352689.jpg

post-1829-1211352740.jpg

post-1829-1211352747.jpg post-1829-1211352759.jpg

Nice thing is the fronts each weigh ~3lbs less then stock...that's a 33% savings... the rears currently are only 1.5lbs lighter but with a different spring they should be the same 3lbs savings.

576 combinations of shock adjustment with separate 24 position rebound and compression knobs. Looking forward to testing them out once I finish changing the cambelts and installing the aluminum radiator.

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Looking good Paul, bet it handles and drive really well :P Was there much trouble setting up the geo?

Thanks Kylie,

Not sure how it handles yet-still in my garage getting it's cambelts changed, but I'm sure it will be vastly better then stock for what I want. What do you mean by geo?

Paul

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geometry

That's what I thought, no changes just got rid of the bushing 'stiction' on the outer bushing with a heim joint, leaving a polyurethane bushing on the inner mount to keep it streetable. The control arms also allow toe adjustments without having to change washers on the radius arm mount.

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I don't remember seeing a rear anti-roll bar on the X180-R race cars (sorry can't post pic, my website is down.

And there is definitely not one on the X180-R street cars.

As Neal said, the chassis is very flexy, and probably leads to alot of the weird decisions on suspension settings.

Here is a good solution for that (X180-R bolt in cage)

x180rrollcagekc1.jpg

I would assume that those cars with rose-jointed suspension links, in the rear, would suffer from decreased roll-stiffness without increased shock valving or spring stiffness.

In the front and rear suspension systems in the Esprit, the rubber bushings provide some of the stiffness since all the suspension arm pivot points are off axis. THe bushings have to deflect to allow the suspension to pivot!

If you replaced the bushings with plastic or metal, the suspension would be totally unable to compress or move at all.

With the rose-jointed assembly they are free to pivot, but they don't have the added stiffness from the deflection of the bushings. More precise, but different.

Though I also assume that anyone who went to rose-jointed links, would also have adjustable or firmer suspension...

Travis

Vulcan Grey 89SE

My Lotus Photo and Projects Album

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  • 4 weeks later...

Bit of an update:

I had the car on the race track last night, did over 200kms which isn't too bad for an evening...lol

Car handled great on with the new suspension, very happy with the balance. I'm also running polyurethane rear radius arm mounts. I am running 450F/400R springs and feel it needs ~100lbs/in front and rear, a bit too much body roll still.

For tires I am running the new Sumitomo HTR ZIII, which performed remarkable well considering I put them through quite a workout. I am used to running on R compound tires at the track on my other car, the grip the HTR's had was very good, far better then expected.

I was also impressed with the complete package of the esprit, excellent braking, power and handling (latter to be expected).

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