996CAB

Am not sure which rear springs system to go for hence the two options.

Am settled on the fronts if I should change them later.

996CAB

Gents,

As noted earlier, here is what I have settled on / looking at;

FRONTS
Eibach Progressive Tender - p/n 0175.250.1300
Eibach Linear spring - p/n 120-60-0040

Gives me following compared to current linear 37 N/mm…;
Soft = 25.7 N/mm
Mid = 30.03 N/mm
Hard = 40 N/mm


REARS - OPTION 1
Eibach Progressive Tender - p/n 0175.250.1300
Eibach Linear spring - p/n 140-60-0050

Gives me the following compared to the current linear 44 N/mm (with GE13 spring assister installed, could be closer to damper rate limit of 50N/mm)…;
Soft = 29.49 N/mm
Mid = 41.01 N/mm
Hard = 50 N/mm


REARS - OPTION 2
Eibach Progressive Tender - p/n 0175.250.1300
Eibach Linear spring - p/n 0600.225.0300

Gives me the following compared to the current linear 44 N/mm (with GE13 spring assister installed, could be closer to damper rate limit of 50N/mm)…;
Soft = 30.51 N/mm
Mid = 43 N/mm
Hard = 53 N/mm


REARS OPTION 1 offers me up to -30mm drop on the rear and thus gives great adjustability using spacers to achieve the ideal drop / rake thus able to manipulate the CG of the car. This option however does not offer enough stiffness IMO. The Eibach spring type being used here only comes in 10N/mm increase thus from 50 N/mm, I can only go to 60 N/mm…not desired as it stiffens Mid and End rate too much thus introducing too much oversteer IMO.

REARS OPTION 2 offers me a ‘closer to’ settings to my current setup in the Mid spring rate and is favoured however the Eibach ERS spring being used only drops the car from stock by 12mm MAX noting that I have to use a spring spacer - which has to be 6mm MIN in depth - to join the two springs. So that is my main concern there that the car will not drop enough and that in turn moves CG towards the front…not desired.

Tough calls here…damn…! Any ideas on how I can get round the above issues or am I worrying over nowt?

996CAB

Paul, I have a question:

On PASM, can you also control rebound...?

On MagneRide I cannot control rebound just compression thus it has been suggested to me that using progressive tender springs with linear will cause an 'over shoot' effect.

The better option is using linear tender and main springs all round. For MagneRide, the use of tender springs is best suited in non-progressive configuration and IF progressive must be used then the main springs would be best option...this specifically relates to the MagneRide where the damper cannot control rebound.

What are your views on above?

997gt3north

William,

I'm busy this am - but will look later.
I want to go over your stuff and figure out the specifics of when the Progressive Tenders Switch over from Soft to Medium to Hard - do you have this handy?

I haven't seen you post this critical piece of data and I just want to make sure that you understand at what load and on each axle will the car encounter the Soft / Medium and Hard Rates.


Paul

996CAB

Paul,
I do not have that data - what I can do later today...BTW it is 14:17 here in the UK...is attach my XLS used for all calcs...hopefully that helps.

For those that may be wondering or thinking...why bother with all this work...well, the car stock from new was 340BHP/450Nm...we are currently 'only running' at S2 of 420BHP/570Nm (may be more however those are conservative figures for now)...I want to improve handling as the next stage which will include a complete engine re-build etc will take us past 600BHP/750Nm... and that would be it...

Mods done so far are as follows;
• RS6 V10 390mm BBK fronts with PFC01 pads / braided lines
• Uprated rear rotors with Pagid RS-19 pads / braided lines
• Endless RF650 brake fluid
• REVO S2 software
• Uprated H&R ARBs
• Uprated lower engine mount
• SuperPro anti-lift front kit (once rear suspension mod is complete I may also fit SuperPro rear kit if required)
• Uprated Proalloy intercooler - good for over 600BHP
• Bespoke exhaust system using Audi Sports exhaust & MillTek parts - good for over 600BHP
• Uprated to Haldex Race ONLY controller

Car looks stock now thus stealth and would remain that way once we are done with power upgrade.

William

997gt3north

I'm sure you also know this but you are currently suggesting mixing 60mm, 2.25" and 2.5" springs so I'm assuming you have all the parts to make sure they fit on your suspension (hats, spring joiners).

Paul

996CAB

Yes am aware of that and will use couplers - these would be made for me or I will buy off shelf. You will note I state that I can play with the ride height…well I was planning on getting the correct depth coupler made as necessary thus as oppose to buying the 6mm depth I may get anything up to 20mm depth coupler made up.

NJ-GT

This is what I use in my Fiat, and what I'm about to use in my Cayman.

My stock Fiat Titanium spring is 4.42 lbs. An Hypecoil 8" 1200# spring is 5.88 lbs. Eibach springs are the heaviest springs out there.

The picture below is from a 6" x 2.25" ID and 560# spring going in my cayman, for drastic weight reduction on unsprung weight.

Lightest and most consistent spring combination, without the discrepancies caused by progressive springs or stiff tender springs. Just linear and consistent response.

My Fiat runs almost 2000# on rear spring rates with revalved Sachs shocks, stiffer rates than most race cars, and it feels smooth at Sebring despite using the stiff shock setting (CST-OFF). On the streets I use the soft suspension mode.

996CAB

NJ-GT...!
I remember your username from years back when I used to drive a bunch of porkers and frequent here more than a lap dancing club...oops, I meant latin dancing club...
...thx for that...

996CAB

Paul - my XLS calcs is attached...

997gt3north

William

I ran some numbers.
Email me and I will send you my quick excel file.

I think you have made a few errors - basically because the Progressive Tender's Block Load is higher than your proposed Main Spring's Block Load - i.e. your mains will go into block and your tender's Upper Rate will then fully kick in - i.e. 1300#s (or 228 Nm)

The other factor I quickly calculated was your proposed dual rate progressive tender (600#/1300#) has the following characteristics
- the 600# section goes into block with 653#s of load
- this section has 1.09 inches of travel
- the 1300# section has .66 inches of travel and takes an additional 860 #s to go into block

So your proposed Front (will definitely not work how you think)
- the 600# section blocks at 653#
- the main 228# (40 NM) blocks at 773#
- then you will get the entire 1300# rate at any weight above 773 #s (i.e. all the time given your front heavy car)
- your proposed Progressive 600/1300 with Main 228 or in Nm (105/228 with Main 40)
- acts like

Soft = 26 Nm (from 0 to 653#s of load)
Mid = 34 Nm (from 653 to 773#s of load)
Hard = 228 NM (from 773#s to 1513#s of load)
Bumpstops

This is clearly not what you want


Your Rear 1
Soft = (30 Nm up to 653#s of load)
Mid = (41 Nm 653# up to 1068#s of load)
Hard = (228 Nm 1068# up to 1513#s of load)

Rear 2
- change Mid = (43 Nm 653# up to 1135#s)

996CAB

Thx Paul...email sent.

997gt3north

William,

What are the stock spring rates on the car Front & Rear as delivered from the factory?

And, you mentioned it is your belief that the dampers are 'valved' for 50 Nm - is that for both front and rear - which is really just asking the first question again?

Just want to go back to the beginning and get some basic facts about the car in as delivered spec.

Some other facts you mentioned
1) Front Axel is 1040#
2) Rear Axel is 870#
3) This gives a car weight of 3820 with a 54/46 f/r weight split
4) but you also mentioned car and driver is 3630?

If 3630 is correct and the f/r weight split is 54/46, then
Front Corners = 988
Rear Corners = 827
(these are not actual corner weights but averages)

Unless you can measure actual corner Sprung weights, you can take a guess that approximately 100#s per corner is not being spring (rim, tire, rotor, caliper, wheel carrier)

This would give Sprung approximate Corner weights of
Front = 900
Rears = 750
(these are gross approximations but if the data is close they won't be far off)

You mentioned 50 Nm shock 'valving' - that would equate to 50 x 5.71 = 285# springs

Is 50 Nm / 285# close to your OE Front / Rear spring rates?


The other thing to do is get some data from some know Suspension Kits for your car
- what spring rates do these kits go with
- you mentioned KW - what are their rates?

Whatever your dampeners are 'valved' to, they can unquestionably accommodate quite comfortably up to a 15% increase in spring rate without any bother at all. It may be as simple as increasing the fronts by 10% and rears by15% to get your desired effect. Or, increasing both by 15% and fitting a slightly large rear bar to increase rotation in the corners. You can also go further by fitting a wider front tire to increase front traction to also help dial out the factory push.

Since your stocks seem to be valved for 'only' 50Nm, Tender / Helper springs may really be unnecessary as it is really with much higher spring and valving rates that Tenders / Helpers become necessary to handle the transitions as the Main becomes unloaded and the wheel into droop (lower rate mains have ranges that usually prevent this.

This does not in anyway mean there isn't a unique multi-tender + main solution that would give you what you are looking for - it is just that there may be easier ways to do it.

There is another Progressive Tender I see in the Eibach list (pn# 050.060.0040.0120)
- I believe the specs they have on the printed pdf file are incorrect - they have it listed as a 40/120 Nm which they incorrectly convert to 238/385 instead of 238/685
- this tender, has a block of 854# (about 150#s above you rear spring corner weight
- this tender crosses over from lower rate at 247#s of load so this Lower Rate will only come into play on wheel droop (which is good)
- if you combined this Tender will a 400# main for your Rear, you could get this profile

Low = 21 Nm up to 195#
Mid = 44 Nm from 195# to 865#s
High = 70 Nm from 865# to bump stops

So basically, the rear corner would ride around at 44 Nm until 150#s additional weight was loaded (a corner or accelerating) at which time the spring rate would increase 20% - this is still something that the car's shock would be able to handle.


Again, there is so many, many possibilities - if you want to tinker, you can have fun.

But, sometimes (most of the times) simpler is better

996CAB

Paul,
Thx a bunch and I have BCC'd you in an email which I think you will find interesting.

I do not know the oem spring rate - however the eibachs that replaced them are 7% higher...that is the only info I have.

Back to your point & questions - thx btw – your comments/questions are noted as Paul said/asked: and my responses are noted as ‘WB says:’ and these are as follows;
WB says: The info below are MAX axle loads…
Paul said/asked:
1) Front Axel is 1040#
2) Rear Axel is 870#

WB says: The car is 60/40 fr/r weight as per Audi.
Paul said/asked: 3) This gives a car weight of 3820 with a 54/46 f/r weight split

WB says: This is a weight I took once with me in the car and 1/3 fuel.
Paul said/asked: 4) but you also mentioned car and driver is 3630?

WB says: best to use 60/40 f/r split.
Paul said/asked:
If 3630 is correct and the f/r weight split is 54/46, then
Front Corners = 988
Rear Corners = 827
(these are not actual corner weights but averages)

WB says: agree with this estimate…I think we can go with these as there is much tolerance anyway.
Paul said/asked: Unless you can measure actual corner Sprung weights, you can take a guess that approximately 100#s per corner is not being spring (rim, tire, rotor, caliper, wheel carrier)

WB says: This was my estimation too though I had the fronts at 1000 kg.
Paul said/asked:
This would give Sprung approximate Corner weights of
Front = 900
Rears = 750
(these are gross approximations but if the data is close they won't be far off)

WB says: MagneRide damper is valved 40N/mm fronts (confirmed by me when car was raised off the ground. 50N/mm (estimate by me as I forgot to read the label when car was last off the ground)
Paul said/asked:
You mentioned 50 Nm shock 'valving' - that would equate to 50 x 5.71 = 285# springs

Is 50 Nm / 285# close to your OE Front / Rear spring rates?

WB says: The Eibach springs on the car is confirmed linear 37N/m fronts and linear 44N/mm rear.

996CAB

Other points to note;
1) I have increased front track by 10mm per corner mainly due to having the BBK. rear track remains as stock.

2) I have larger ARBs from H&R fronts & rear. Fronts set to soft and rears set to hard.