996CAB

Paul,
I have now digested your response and that has brought me back to spring specs that I had looked at previously which as you note would work well.

IN REGARDS TO THE FRONTS
The interesting point here is that, when I use same progressive tender spring mentioned - 40/120 N/mm - for fronts, the car will be riding around 35N/mm (the current spring rate is 37N/mm). In my opinion, the current fronts do not need changing and the car drives well as it is…I always felt the rears just needed a change anyway…which is all good.

IN REGARDS TO THE REARS
Again another interesting observation here from your notes…when I use same progressive tender spring mentioned - 40/120 N/mm - for rears, the car will be riding around 44N/mm (the current spring rate is 44N/mm…!).

In my opinion, the rears changed as you note below WOULD give me exactly what I am looking for - a progressively stiffer rear.
Low = 21 Nm up to 195#
Mid = 44 Nm from 195# to 865#s
High = 70 Nm from 865# to bump stops


So, from my perspective the following is my summary;
1) The numbers from calcs look good and reflect 1st hand experience being that the current spring rate of 37N/mm fronts and 44N/mm rears matches well to the calcs suggesting 35N/mm fronts and 44N/mm rears.

2) The main advantage of the calcs from the numbers above is that specifically on the rears it does support/suggest I can go up to 70N/mm…which again mirrors my 1st hand experience that a stiffer rear (as I have proven with fitting the Grayston GE13 spring assister which stiffens the rears by an estimated 15% though raises ride height by 5mm) and leaving the fronts where they are will give me a much balanced car.

3) The only thing I need to address is the ‘nervousness’ attitude of the car mentioned by my tuner when he compared the car to his KW V3 and KW Clubsport fitted cars…am not entirely sure that single issue will be fixed with the change however it is worth a try.

Anyway, as we say on the streets of Sarf London, UK – "the science supports the theory & bum dyno…!"

Paul, you beauty and thx very much…!

Now I will go and fit the required Eibach ERS springs, test and feedback…likely to be Jan given X’mas.

Nordschleife

I have only picked up the tail end of this thread, so apologies if this has been posted earlier

http://www.rentoncoilspring.com/perf.../why_titanium/

this Janet'nJohns you through the Ti/Cr-Si Spring debate.

Also, most importantly, I think its a good idea to exactly verify your spring rates. Margins of error can be excessive and I have known cases where people planning to go firmer (on nominal values) actually went softer (measured deflection).

I have done some proper chassis testing for more than one German manufacturer, sorting out actual spring rates before trying to do anything else is always a priority.

Making friends with your spring and shock suppliers is always helpful. Much as I like the guys at Öhlins, I must admit that the Sachs team have a better espresso machine, which is the most important piece of tuning kit in continental Europe.

R+C

996CAB

Thx for the comments and the link...

996CAB

UPDATE: 19th Dec 2011

Well,
Paul and I have moved things on in the background and I have ordered the following Progressive Tender + Main Spring from the Eibach ERS range;

Low = 34 N/mm up to 653#

Mid = 51 N/mm from 653# to 1513 #s

High = 66 N/mm from 1609# to bump stops

Progressive Tender Spring: 0175.250.1300

Main Spring: 700.250.0375

CAR WEIGHT (estimated MAX): 1,111 Ibs front /// 740 Ibs rear

Am pretty excited as the calcs looks good and now I have a better understanding of how tender + main springs work am expecting the following to occur...;

A) The tender spring will be at blocked height due to rear weight being greater than the weight the tender supports before being compressed in to block height...thus the tender will be already compressed and main will be active. On rebound the TENDER then becomes active...in theory this will make the ride softer in rebound.

B) The main spring being active will give me the firmer ride I want on compression...tests I have conducted has shown that the car handles much more precise and composed when the front suspension is softer to rear suspension.

Due to the rebound character of the tender spring I expect a softer ride and I will explain...

• my current setup on the rears is at 44 N/mm on compression and 44 N/mm on rebound...new setup will be 51 N/mm on compression mostly due to tender being at block height and 34 N/mm on rebound due to tender coming active from block on rebound...S I M P L E S...that is the theory anyway...we shall find out the facts after fitment...

The above spring operation will mean that my MagneRide dampers will work extra time due to the variant spring rate coming in to play more often compared to a linear spring rate.
In my opinion, this is the greatest value of a MagneRide due the dampers ability to, reportedly, react to changes 1000s quicker than a conventional damper.

Though perhaps a touch early however I really must say that Paul has been extremely helpful behind the scenes to...;
1) Educate me on the operation of tender + main springs.
2) Pull calcs that makes sense and gives confidence to explore.
3) being patient - this 'ol fool needs kid gloves treatment some days...!!!
4) Taking the time to read the many info I kept bombarding his InBox with...!!!
5) Direction above all to help me order what I now feel will work.

Thx indeed Paul...

996CAB

UPDATE: 5th Jan 2012

Car has finally been booked in to my tuner to get our theories in to practice. Action plan are as follows;
1) Weigh the car.

2) Revise calcs based on weight info.

3) Keep springs bought or return those not needed and order new springs - assuming #2 above forces a change.

4) Fit parts and test on track...fine tune as neccessary.


Spring rates aimed for ON REARS ONLY are as follows;
Low = 33N/mm (189Ibs/inch) up to a load of 653Ibs

Mid = 48N/mm (276Ibs/inch) from a load of 654Ibs to 1513Ibs

High = 61N/mm (350Ibs/inch) from a load of 1514Ibs to bump stop


Parts used
Eibach Progressive Tender Spring: 0175.250.1300

Eibach Main Spring: 0700.250.0350

Eibach coupler: Spacer250

Bilstein ride height adjuster: apologise, no p/n to share

If the above changes works as we expect then I will apply same principle for the fronts.

I will feedback after fitment...Happy New Year ya'll...

END

996CAB

Hi All,
We have now made the change and I wanted to share the change with you...

Before that a big thanks to Paul...what an eye opener with your work on PASM and now stacked springs...great guy...!


I solely want to concentrate objectively on the following...;

1) what we have done;

2) why we did it;

3) comparisons to before;

4) next steps...;

5) the results;


1) What we have done - in a nutshell, I have kept MagneRide on all fours and replaced the rear linear springs for a double stacked spring arrangement with triple spring rate action...a petrolhead friend has tried this on his PASM equipped 997 GT3RS however stacked linear tender and linear main...I have taken his idea a step further by using progressive tender springs with linear main springs...best of all, it is adjustable thus we can go lower by up to 20mm and higher by 30mm from the previous height.

2) Why we did it - to improve the handling and improve ride comfort; to prove that C/O kits is not always THE only & best option; to prove that MagneRide dampers are better than most realise.

3) Comparisons to before - Chalk & Cheese; Yin & Yan; Black & White; Night & Day...I really could not put it any other way...read review below for further details.

4) Next steps...; Trips to trackdays to test out further then we will replicate what we have done to the fronts.

5) The results - Let me break it down in to areas...NOTE: previous rear spring setup was Eibach 44N/mm + Grayston GE13 giving a combined 51N/mm spring rate.



Part-1 test;

- the ride in the harder MagneRide mode is now much softer than my previous setup in the softer MagNeride mode.

- the great thing about the previous setup was that steering had lots of feedback and the car felt well planted. Turn-in was razor sharp. All of that trait is retained.

- composure over bumps is now not an issue...previuosly, when in the harder Magneride mode, the rear of the car will jump around as if it was on the bumpstop and this caused the fronts to also jump around when you hit a bump...now the rear suspension simply soaks up bumps and thus enables the fronts to remain in control.

- squatting is now gone......THIS WAS THE VERY TRAIT I HATED MOST ABOUT THE PREVIOUS REAR SPRINGS AND WANTED TO RESOLVE!...the new rear can take the load at WOT now that I have up to 88N/mm spring rate to assist MagneRide on compression...rebound is not affected. Squatting was a real issue before as it caused the fronts to go light thus steering lost control/feel and became in-precise...now, the fronts remain planted at WOT thus enabling the car to be adjusted mid corner with ease.

- braking is not affected on WOT to hard stop or hard stop in corners...car pulls up straight.


Part-2 test;

1) B-roads - Sports Mode ON thus harder suspension settings;
Ride; Handling compared to before - softer; compliant; loads up nicely on hard cornering; car is very composed. Reminded me of the MagneRide equipped R8 V8 I drove on track...my MagneRide equipped TT-RS is now just as composed. Turn-in is sharp and precise as before. The car can be thrown in to a bend and it stays in that trajectory riding the road well until I change cause. The key here really is that the suspension soaks up bumps and the squatting when cornering is gone so the fronts stay in contact with the tarmac thus the car feels planted; ready to change direction and composed all at the same time.



2) A-roads - Sports Mode ON thus harder suspension settings;
Ride; Handling – no different to above. In essence the suspension is very capable on B-roads and shines more so on A-roads…so the drive is a much relaxed affair.



3) Motorways - Sports Mode ON thus harder suspension settings;
Ride; Handling – Ohh, much more relaxed affair…does not follow camber as before and the occasional WOT to get in to a gap or keep up is more urgent and drama free. Interestingly, I detect now that I have ‘more time to think’ and am finding the car now feels ‘underpowered’…yeah, it still has REVO S2 with 420BHP to 435BHP of power. Anyway, just goes to show what a well sorted suspension - all be it on the rear axle only for now - does to road holding.

In the non-Sports Mode thus softer suspension, the handling/composure is same as above however it is just so damn more comfortable compared to before…which then plays a different game on the senses as the actual speed I am travelling at ‘feels’ much less thus at 80MPH it does feel more like am doing 50MPH/60MPH…got to watch that because that is a license killer…!

This has been a great upgrade which cost me £690 all in.

The fronts will cost a little bit more though will be under £1k because we do not have the luxury of room/height to play with and I will need to get some parts specifically made up.

In summary, am happy and the car now feels right on all roads I care to drive on so am confident it will perform well on track.


Part-3 test;
Just wanted to finsh off to say my drive back home this evening was extended so that I can do further street testing...and the rear spring is just such a revelation...interestingly, there is no performance difference between the harder MagneRide settings and softer settings...seems like the springs are doing all the work and loads up nicely. The transition from the 46N/mm to higher rated 88N/mm is seamless and not felt.


Thx for reading and enjoy/discuss...lots of pix attached...



Corner weight info car had 1/3 fuel;
Passenger side front 451kg
Drivers side front 486kg

Passenger side rear 309kg
Drivers side Rear 318kg

Total = 1564kg




Just so there is some balance here are the negatives;

1) Will cost more than a KW v3 fitted...however I do get to keep MagneRide functionality.

2) I could see myself easily losing my license...this thing can shift & corner really well.

3) It has been tedious having had to endure a steep learning curve on all things Stacked springs...I know enough to get by now though...!

4) I have to do it all over again on the fronts...hmmm, damn it...!

5) I do not know how it will affect MagneRide long term.


Final Spring Rates
Low = 22 N/mm up to 196#s

Mid = 46 N/mm from 197#s to 865#s

High = 88 N/mm from 866#s to 1810#s

997gt3north

For all you guys at Sebring,

I'm serious glad William decided to run with this and give you an idea of what is possible. Basically, build a suspension that rides around on Tenders of your desired rate, and then when you load the car by about 200#s it switches to the higher spring rate.

To do this, you need to know your Sprung Corner weights with driver and you pick a Spring (Tender in William's rear suspension example), that will go into coil bind a couple hundred pounds above this.

The Mancation boys know that Mosport isn't this type of track so I won't be doing this but I strongly believe this is a great solution for the a certain few.

Back to the regularly scheduled 'cheater' program.


Paul

996CAB

Thanks Paul and I really am grateful for your PASM thread and this thread - both lead me to the rear setup I now have and am now looking forward to do the same to the front axle.

Yet again, thanks for your continued support...

silverboy

I am having mental indigestion.

So a tender/helper set up is similar to a progressive spring rate set up ala EX-TC?

I now have 600/900 (dunno what helper rates) and Moton CS.

I was thinking of getting a spring with a progressive rate w/ all the fuzz after the EX-TC expose. Should I?

The roads I drive in and track is bumpy.

utkinpol

a quick note - in the picture below where you have a joint between tender and main spring - take a piece of electrical tape and wrap it around there to bond 2 springs with a spacer together - it will eliminate springs rattle on bumpy roads down to minimum. it took me quite some time to figure this out, actually, as i could not understand where that rattle was coming from.

as of progressive rate tenders - my mechanic told me it is bad for handling, and whole/only point to have tenders in the setup is to reduce rattles a bit on the street, 'normal' race cars he builds do not have any tenders at all, just linear main springs. in his opinion rate of tenders has to be much less then weight of the corner so it would be 100% collapsed all the time, so he uses 150# tenders on all corners.

997gt3north

You really have to read the entire thread to get what my idea was. It wasn't to add tenders or helpers to your existing 600/900 setup, but it is to setup a car that would say ride around at 250/500 but with any load would jump up to 450/750. This is what William has done with his TT-RS. This isn't for everyone for many reasons as it takes some work to figure out the springs you need and you have to know your Sprung Corner Weight with Driver so you can pick the exact crossover load where the car jumps up to the higher rate, but after working with William and getting his feedback I'm certain it will work - and you could do it without revalving your suspension.

I think it has worked out so well for William that you can expect a kit to be coming out for the TT-RS.

There is a lot of detail in the early pages of this tread that you have to read to understand the idea.

Paul

utkinpol

i am not sure i understand what actual benefit it gives to have an additional transition from 250# into 450# rate while you are mid-corner.
whole point to put linear springs is to make suspension pre-load more predictable in all transitions so it improves steering control, so, what gives?

996CAB

If I can just make a couple of points which are not in my review however Paul is privy to these...;

The setup I have was done about two weeks ago by my tuner - I will not bore you with his credentials however his workshop setups cars for current teams competing in various British motorsport events /// he also owns a couple of cars used to demo his work and one is fitted with KW v3 and the other fitted with KW Clubsports - he tested the car over 10 days before releasing it to me. He had proposed KW Clubsport prior to the fitment...not anymore...!

In his tests, he could not fault the setup - yes, he had doubts before we started however all that 'theory doubts' were blown away by how the car feels and drives...the theory and implementation worked...we can debate why it should not work for another 1000 years however it really will not change the way the car feels now compared to before...S I M P L E S...!

We will be going out on track to test further - he just wants to 101% assure himself that it really is a great 'find'...then we plan to package what we know for others IF they want it.

997gt3north

There is no magic here,

A long time ago when I began this tread, I did so after much research after I revalved and re sprung my stock suspension in my 997gt3. Along the way, I came across many good posts from here and articles from other places that got me thinking about setting up a GT3 in a way that might be good for bumpier tracks - like Sebring - it also coincided with some postings about a particularly fast car at Sebring that uses a custom suspension (TC) that is infact 'softer' than your typical 700/800 upgrade.

My idea was that without revalving your shocks, you could get more / better performance on bumpy tracks by just changing the springs - but in a very particular way - and that way was to set the car up to ride on slightly softer initial rates than the OE 240/600 rates for the mk1 - as an example 200/450, but these inital lower spring rates would when further loaded for example while brake, turning or accelerating kick up to better / higher rates that would help with too much weight shifting around.

William, who has posted these pictures has basically done this but in a slightly different manner - he also upped the initial spring rates.

From an everyday driving perspective, this is also what most people would like - ie softer springs until you need more - and then you get more.

utkinpol

did you try to run at sebring with those various setups? that would be very interesting to look at, how those ideas really work.
it all sounds pretty logical, i do not argue with that.