Bilstein/Eibach suspension Version 2

[RayD]

As Bob says, using the formula even for two identical springs ...

200 x 200 = 40,000 divided by 200 + 200 = 100

Placing a 100lb weight on two 200lb/in springs would cause them to compress ½” each.

Spings.jpg

Ray

[knoxmotorsports]

Right. It is confusing at first, but we are talking about helper springs here...they are designed to fully compress with 1-2" travel usually. After it reaches coil bind, it cannot go further, so the other spring begins to compress at its spring rate

[surfboardfiller]

As Bob says, using the formula even for two identical springs ...

200 x 200 = 40,000 divided by 200 + 200 = 100

Placing a 100lb weight on two 200lb/in springs would cause them to compress ½” each.

Spings.jpg

Ray

Only if the springs were side by side would the compression be devided, but they are not, they are on top of each other.

[bobbrown]

Afraid to say that if pair of 200lb/inch springs placed on top of one another and a 100lb weight is placed on top, each spring compresses 1/2" so the total travel is 1"
This is due to the full load acting on both springs at the same time so each spring in effect has 100lbs on it.

Bob

[RayD]

Phil, not being one for accepting things because they are too complicated to explain I tried to explain it ...

You are right in saying “Only if the springs were side by side would the compression be divided”

It is divided when they are side by side, it’s the reason a sprung mattress hardly moves when you lay on it.

When they are end to end it might be better to say the effect is multiplied.

With the two 200lb/in springs on top of each other the bottom one has the 100lb weight plus the weight of the top spring acting down on it. It would in fact move approx ½''

Ray

[surfboardfiller]

Phil, not being one for accepting things because they are too complicated to explain I tried to explain it ...

You are right in saying “Only if the springs were side by side would the compression be divided”

It is divided when they are side by side, it’s the reason a sprung mattress hardly moves when you lay on it.

When they are end to end it might be better to say the effect is multiplied.

With the two 200lb/in springs on top of each other the bottom one has the 100lb weight plus the weight of the top spring acting down on it. It would in fact move approx ½''

Ray

Of course it would.

[RayD]

Thanks Phil,

Ray

[bobbrown]

I need the numbers to get to at least 20 in this group buy viewtopic.php?f=85&t=15962 to get a reasonable discount and the next break point is 40 but I do not see us getting to that point

Bob

[RayD]

Would it be a good idea to ask Nitron what the original spring rates and lengths were for the SE and Fed cars? Perhaps they could list the choices available from Eibach showing a range of springs in increments from the original to full race in terms of rate and length, and if appropriate what span of increments a particular damper covers. It may make it easier for people to choose rather than describe it as “80% towards track set up” or “race set up”

A few observations...

I can't quite picture how changing the spring rates would raise the car up.

Quite simple really. If the front had say 250 lb/inch springs and the load on the spring was say 750lbs then the spring would compress 3" if you substitute the 250lb spring for one of say 300lb/inch then the spring only compresses 2.5" for the same load.

Until now you would have thought spring rates were an important feature of Lotus suspension.

You could imagine them identifying the optimum rate for the SE through calculation then fine tuning it with hours of testing.

Using some of the figures mentioned here ... suppose Lotus decided on 250lb/in for the front of an SE. With the front of the Fed car being 3% heavier it would be reasonable to think they might have fitted 260lb/in for the USA ... but ...it needed to be an 1” higher so they seemingly fitted 375lb/in springs instead. I wonder why they didn’t just fit longer ones.

With it being universally accepted that aftermarket springs need to be 20% stiffer than the original a 375lb/in one in America would become 450lb/in. Whichever way you look at it it’s a long way from the original 250lb/in.

If the rates were ever doubled for a race set up the gap becomes even wider, 500 and 750.

If they are using stiffer springs to raise the ride height are they using softer ones to lower it?

I wonder if the effect of the anti roll bar starts falling off as the spring rate increases to the higher values.

Does anyone know the outcome of the Esprit exercise was when Lotus became involved in testing and how the most popular new rate and height compared to the old?

Ray

[rip]

A few questions to answer there...
My new springs are about 30% stiffer than the originals. It copes with bumps better than the originals, which I expect is because the old dampers were worn. The stiffness helps to keep the car flatter around a bend/roundabout. Dico & Gazza remarked about this when they took my car out the other night.

My Nitron dampers have spring collars to adjust the ride height. The spring will always stay the same length as its working length is determined by the weight of the car. If you want to raise the ride height, raise the spring collar. Unless you adjust it too far, the damper will stop the spring from compressing or expanding too far.

The anti-roll bar will provide the same resistance to rolling regardless of springs. Stiffer springs will add to this resistance so the overall effect will be that the car corners flatter.

I'm sure Bob will be along soon with some more answers & probably corrections to mine too.

[bobbrown]

Ray,

Getting accurate figures for the original springs is quite difficult as over time they will have deteriorated and you really need new springs. It would appear on the face of it that Lotus did a couple of things to the springs on the Fed cars all be it only really at the front due to the slight increase in weight and possibly the change in ride height.

I do not think the Fed cars had front springs at 375 lb/in 330 lb/in is probably more like it with the standard SE at about 290 lb/in, it all gets a bit complicated as you need to maintain droop, bump and spring preloads. As the spring rates go up the only way to maintain the droop is to fit helper springs other wise you could end up in a situation where when the car is static the travel to full droop is zero e.g. the front springs are 750 lb/in and the weight on that corner is 850lbs with 100lbs of preload droop zero.
It is probable that Lotus did fit longer springs to the Fed cars and increased the preload to get the Fed cars up but as far as the rears are concerned it looks like they may have just increased the spring rates but again working with second hand suspension trying to get figures it a bit of a calculated guess.

As for the anti roll bars the front is relatively light as it is tubular but they only do anything in roll hence the name, dive under braking in a straight line they do absolutely nothing

As for a selection of spring rates for different applications road, occasional track day, of a more aggressive setup then all are possible and it is just a case of making the choice of what you want.
Iain’s car seems a lot better in terms of roll with out any loss in comfort and it may be possible to increase the spring rates even more with very much loss in comfort. In the main this is due to the change in the type of dampers fitted but it could also be due in part to the original setup being well past its sell by date. Lets not forget dampers wear and I would hate to think how many times they have been up and down, not just the long travel either but there is a lot of higher frequency stuff they have to contend with from the road surface it's self for one.

[bobbrown]

A few questions to answer there...
My new springs are about 30% stiffer than the originals. It copes with bumps better than the originals, which I expect is because the old dampers were worn. The stiffness helps to keep the car flatter around a bend/roundabout. Dico & Gazza remarked about this when they took my car out the other night.

My Nitron dampers have spring collars to adjust the ride height. The spring will always stay the same length as its working length is determined by the weight of the car. If you want to raise the ride height, raise the spring collar. Unless you adjust it too far, the damper will stop the spring from compressing or expanding too far.

The anti-roll bar will provide the same resistance to rolling regardless of springs. Stiffer springs will add to this resistance so the overall effect will be that the car corners flatter.

I'm sure Bob will be along soon with some more answers & probably corrections to mine too.

The spring platforms only allow a small amount of adjustment in terms of ride height and their real job is to adjust corner weights to lower the car it should be done by reducing the damper overall length but you have to take the clearances at full bump (suspension fully compressed into account) as it can in this case foul the wheel arch liner on the front. To get the Elan lower then I think a combinaton will be required of shorter dampers and a slight reduction in suspension travel to stop the wheels hitting the liners but all things are possible.

Bob

[RayD]

Thanks for your replies,

Iain,

It’s inevitable it will feel flatter cornering with stiffer suspension. Coping with bumps better is probably down to the new dampers as you say.

In extreme cases the anti roll bar won’t be capable of compressing the inside spring. I don’t know the capabilities of the standard ARB but there will be a limit to it and it may be less than it would need if the springs were say twice as strong. You would gain one thing and lose another.

Bob,

You would have thought the leading spring people would have a method of identifying within a few pounds what the original spring rate and length was.

Turton’s in Sheffield suggested to me to ask Lotus, they seemed to think they wouldn’t mind parting with the information to a private individual. Is anyone well in with someone at the factory?

I’m not suggesting Fed cars had 375lb/in springs – I have no idea what they had – I’m saying by using stronger springs to increase ride height by 1” they are going a long way from where they started, as though the spring rate was unimportant.

“As for a selection of spring rates for different applications road, occasional track day, of a more aggressive setup then all are possible and it is just a case of making the choice of what you want.”

I understand but in normal life when someone gives you that option you're likely to ask “what have you got” Some might vaguely remember this happening at the beginning of a party

It seems as though they have the springs already and they must go up in increments and they probably have them in different lengths.

It may be possible to place an order in percentage terms e.g. Standard or +10% or +20% +30% +40% +50% up to whatever they suggest is unsuitable for normal road use.

After hearing reports a person then might specify +30% standard height +40%, 1” lower or +20%, ½” lower. It just seems more positive than relating it to the time it might spend on a race track.

If mine ever started off at the prescribed ride height it has settled down approx 5mm in 40,000miles.

Ray

[bobbrown]

You would have thought the leading spring people would have a method of identifying within a few pounds what the original spring rate and length was.

I do not think that is possible with out some very complex and very costly work to find out just exactly what material was used ok you can get an idea what a spring is but what was it to begin with is an educated guess. It could have softened over time or work hardened over time and with out knowing what it made of.................
If you look at the size of the spring on the original setup and that of the new springs the first thing you notice is the diameter of the wire, the new springs use a wire that is considerably smaller in diameter than the originals and thus a lot lighter this is due to the material being used which is far more expensive than the original material.

I do not want to get involved with too many setups as this can lead to confusion and it is bad enough as it is with probably 3 or may be 4 springs and two ride heights standard and -1" going any more than -1" is just not an option due to constraints with in the suspension and the fact you would lose much more than you could possibly gain. Spring lengths will remain the same and have no effect on ride height what so ever as the spring platforms are adjustable the only time the spring length has an effect on ride heights is if the spring seats are fixed as per the OEM setup. The only restriction in spring length is, can you get them in and do they go coil bound before the suspension has reach full travel, the latter is quite critical as it can lead to spring assemblies being smashed out through the bonnet.

Bob

[RayD]

Bob,

I was trying to reduce the confusion.

There was a point a few posts ago when it seemed there was no end to the permutations available. It’s a good idea to limit the choice as you say.

Considering what’s been said earlier by specifying (80% towards trackset up) a buyer may expect his will comprise of 460lb/in springs (front) and sit 20mm lower.

Someone specifying (race setup) may expect his will be 580lb/in and sit 1” lower.

“Standard” (+30%) 380lb/in at the standard ride height.

(Federal), 3% stiffer than “Standard” and sit 1” higher. ???


Regardless of the complexities, Nitron must know which Eibach springs are suitable for the Elan and which of their dampers match up. They’ll know which most closely matches the original set up and from experience know which would produce the various effects people are asking for. I’m thinking it would be better if they said what options were now available for the Elan and how the various options would perform compared to the original equipment.

It might be that all the people on the list fully understand it, in which case, fair enough.

I’m confused how on the one hand we can have conversations about adjusting spring rates to account for minute changes in weight, or even more minute changes in the weight on the corners of the car, but end up with vast differences in eventual spring rates.

Ray

[RayD]

According to the Internet the standard springs for a Honda Type R are 250 front 250 rear, although one person says the rears are 240

On the Nitron website their kits for the Type R are

Sport ........300/350
Track........300/350
Race.........300/350

An increase of 20% at the front

If you have a look through the other models you’ll find a lot of them have the same slightly upgraded rates regardless of the application.

Ray

[bobbrown]

If my figures are correct fo the Elise then standard they run some thing like F 190 lb/in R 267 lb/in standard

From Nitron's web site the Elise gets
sport 425 lbs/in front, 550 lbs/in rear.
track 475 lbs/in front, 600 lbs/in rear.
race 600 lbs/in front, 700 lbs/in rear.

on a lighter car than the Elan

There is a consideration of the motion ratio and damper angle to be taken into account as the load on the wheel will not be the same as the spring rates due to angles of the suspension and the motion ratio.
Motion ratio is the distance drom the suspension inboard pivot point to the spring mount and the centerline of the wheel.

Motion ratio.jpg

image c/o Eibach

So a 300 lb/in spring may only subjecting the wheel to 200 lb/in I do not have the figures but Eibach did the original calculations from parts, information and drawings I supplied.

In the case of the Type R it may well be the motion ratio 0.98 or 1.02 which is more typical for strut type suspension so a 350 lb/in spring gives just about 350 lb/in at the wheel.

So in our case a increase in spring rates from 300 lb/in to say 400 lb/in does not increase the stiffness by 1/3 but considerably less although the spring rates have gone up by 33%
In the case of the test car we probably only increased the "stiffness" by around 10% and in the case of the track day cars it may go up by 50% although the spring rates will probably be + 500 lb/in an increase in excess of 75%
As I have said before it is quite complex with a lot of number crunching

Bob


Bob

[RayD]

There is a consideration of the motion ratio and damper angle to be taken into account as the load on the wheel will not be the same as the spring rates due to angles of the suspension and the motion ratio.

....So a 300 lb/in spring may only subjecting the wheel to 200 lb/in I do not have the figures but Eibach did the original calculations from parts, information and drawings I supplied.

In the case of the Type R it may well be the motion ratio 0.98 or 1.02 which is more typical for strut type suspension so a 350 lb/in spring gives just about 350 lb/in at the wheel.

So in our case a increase in spring rates from 300 lb/in to say 400 lb/in does not increase the stiffness by 1/3 but considerably less although the spring rates have gone up by 33%

In the case of the test car we probably only increased the "stiffness" by around 10% and in the case of the track day cars it may go up by 50% although the spring rates will probably be + 500 lb/in an increase in excess of 75%

As I have said before it is quite complex with a lot of number crunching

Bob,

I understand motion ratio. It applies to the original springs as well.

If it were the case that increasing the spring rate by 75% would only increase the effect by 50% it’s something that Nitron explain in their write up.

At the minute I can’t see how it can only effect the new springs?

Does the Nitron kit change the Motion Ratio?

(9/14)=0.64(x 0.64) = 0.41 x 300 = 123 at the wheel
(9/14)=0.64(x 0.64) = 0.41 x 400 = 164 at the wheel
(100/300) x 400 = 133% = 33% increase in spring
(100/123) x 164 = 133% = 33% increase in effect

When you say things are too complex to explain I’m trying to make them less complex, easier to understand, so people can make a more informed choice.

With regard to the examples on the Nitron site I was pointing out how a large number have the same spring rate throughout the various applications Sport, Track and Race, whereas on here the relationship between more track use and higher spring rates seems disproportionate.

I had seen the Lotus Elise figures, they were the first ones I looked at. If you pick a car at random, just now I chose a Ferrari 355, there’s a good chance the spring rates are the same throughout.

I’m sure there’s a reason for it, and for the Lotus Elise, and there’ll be a reason for them choosing whatever they have for the Elan. I’m just suggesting they could let people know what it is.

Ray

[bobbrown]

Ray

If you understand motion ratio as you say you do how can you say "Does the Nitron kit change the Motion Ratio?" as this would mean changing the position of the damper in relationship to the lower arm, do not think that is going to happen. We are only talking about spring and damper changes not changing any other suspension components and motion ratio does effect all spring settings old, new and worn as is is a function of the suspension geometry and if you want to be pernickety, where the wheel is positioned static, full bump and full droop and any other position in between.

Dot not follow these figures at all or where they came from ...
(9/14)=0.64(x 0.64) = 0.41 x 300 = 123 at the wheel
(9/14)=0.64(x 0.64) = 0.41 x 400 = 164 at the wheel
(100/300) x 400 = 133% = 33% increase in spring
(100/123) x 164 = 133% = 33% increase in effect

I did not say, things are too complex to explain, I said "As I have said before it is quite complex with a lot of number crunching" which is different.
It requires the use of computer programs to sort out all the detail as there are a number of other things to take into consideration like the inboard bushes as the wishbones are not held on a friction free pivot, unsprung weight velocities etc. What do you want, to be led by the hand through the intricacies of spring selection which on the most part is done by computer and people who have the experience to work these things out.
At the end of the day it takes a lot of time and a lot of testing to get it right and even after a year it may still not be 100% even the F1 boys do not get it right all the time and they have huge budgets.
I could have said OK lets get a bucket full of springs and dampers of what we think should be the correct settings and go off to the track and spend a couple of days or even a weeks testing, as if any one is going to pay for that.
The Elise gives people like Nitron a much larger market where as the Elan they are not likley to see a vast fortune in developing a spring/damper combination
If you want to do it feel free to take this one over as I have no problem with that.
As it stands it has cost me in excess £200.00 of my own money which I am never going to see back and that does not account for the time I have spent on it.

Bob

[RayD]

If you understand motion ratio as you say you do how can you say "Does the Nitron kit change the Motion Ratio?" as this would mean changing the position of the damper in relationship to the lower arm

You’re right Bob, I wasn’t expecting they did – it was the only thing I could think off that would account the motion ratio affecting the spring rate differently from old to new. I’m sorry about that.

Dot not follow these figures at all or where they came from ...

(9/14)=0.64(x 0.64) = 0.41 x 300 = 123 at the wheel
(9/14)=0.64(x 0.64) = 0.41 x 400 = 164 at the wheel
(100/300) x 400 = 133% = 33% increase in spring
(100/123) x 164 = 133% = 33% increase in effect

I roughly checked the TCA length (14”) and damper pivot point (9”) to get the MR (9/14)² of 0.41 and applied it to a 300lb to get the 123lb at the wheel. Did the same with the 400lb to get 164 at the wheel. Then the third line … 400 is 33% more than 300 and 164 is 33% more than 123.

It doesn’t matter that the MR may be wrong - until someone explains differently I can’t see how changing a spring rate by 33% can result in anything other than a 33% change at the wheel

I did not say, things are too complex to explain, I said "As I have said before it is quite complex with a lot of number crunching" which is different.

It is different as you say. It still seems to mean that the subject shouldn’t be explored, and just accepted.

It requires the use of computer programs to sort out all the detail as there are a number of other things to take into consideration like the inboard bushes as the wishbones are not held on a friction free pivot, unsprung weight velocities etc.

I made this point earlier, it’s hardly worth bothering making a miniscule adjustment to the spring rate to account for the effort in turning the wishbone if the rate is going to randomly increased later.

What do you want, to be led by the hand through the intricacies of spring selection

I don’t want anything – as Dapinky once pointed out - "I suspect you have a sneaking suspicion of the answers to these questions already, but have asked to get clarity for the forum"

If you want to do it feel free to take this one over as I have no problem with that.

I don’t want to take it over but I’m happy to help in any way I can.

Ray