??spring rates??

[Bill Verburg]

i'm tring to figure ou which set of springs to start out w/ on my JIC suspension setup.

The JICs appear to be much stiffer than the other usual suspects in the suspension upgrade department.

But...

I started looking at 993GT2 springs and was shocked.

JIC

kg/mm	   lb/in     kg/mm	 lb/in

7	391.1599974	10	558.7999963

8	447.039997	12	670.5599956

GT2

N/mm	kg/mm	lb/in

270	27.5	699.3213722

296	30.2	766.6634303



Did i mess up somewhere?

[Tom W]

The 7/10 JIC are the middle range? I never did the calcs, but they are more than firm enough for me. I run mine at about -6/-4 from full firm (IIRC) and have been making them softer as the year progresses (and getting faster). FWIW I have 25/23 for sways set at middle/soft.

Setting the JICs at full firm or -3/-2 made cornering difficult and I got a lot of wheel hop in tighter corners. Softer was better. I will continue to play with the settings at Sears Point on Monday.

[Don Plumley]

Bill - your first set of numbers converting kg/mm to lb/in work for me. I found this online:

1 newton = 0.2248089 pound-force
1 millimeter = 0.0393701 inch

0.2248089/0.0393701 = 5.710143

N/mm * 5.710143 = lb/in

So 270 N/mm is some 1541 lb/in. Something's not right...

[Bill Verburg]

The #s for the GT2 came directly from the factory manual.

270-320 N/mm front
296 - 350 N/mm rear



when compared to the JIC or others that is incredibly stiff.

My feelings are w/ Tom, around here the both track and street are pretty lumpy.

Don, Have you gotten yours on the road yet?

I'm thinking the 7/10 would be a good place to start.

[Don Plumley]

I drove it home on Thursday. I have the middle set - 8/12 if I recall. Going down a driveway it lifted a front tire easily. On bumpy road surfaces, it's by no means comfortable. But I had the adjusters pretty tight, it would be interesting to see the difference with them on full soft.

I think that Bob recommended the 7/10 for mixed use, but with my 90%+ track in mind, we went with the next stiffer. It's pretty stiff, I'm running it at Infineon on Monday and will have a better idea.

[Bill Verburg]

Something's not right...

Agreed
here's the updated data
JIC 7/10 linear

N/mm	kg/mm	lb/in

68.7	7	392

98.1	10	560

JIC 8/12 linear

N/mm	kg/mm	lb/in

78.5	8	448

117.7	12	672

993RS progressive

N/mm	kg/mm	lb/in

43	4.4	246

80	8.2	457

GT2 light

N/mm	kg/mm	lb/in

270	27.5	1542

296	30.2	1690

GT2 stiff

N/mm	kg/mm	lb/in

320	32.6	1827

350	35.7	1999

[Tom W]

Bill: do you happen to know the colors of the JIC springs? I've always thought I had the 7/10 but the info that came with did not specify what they were. Mine are purple.

[Don Plumley]

Tom - Mine are purple and are 8/12. That's the middle one.

[Bill Verburg]

They are all purple, marked on the ends

7kg/mm is 11.25mm wuire
8kg/mm is 11.62mm wire
10kg/mm is 12.2mm wire
12kg/mm is 12.63mm wire

they are also available in 9 & 11 kg/mm for 993/964 use

[Don Plumley]

Purple is my only complaint.

Bill - my fronts out of the box had the helper spring on the bottom of the shock if it matters at all:

[Tom W]

Thanks guys. Was sure I had the middle of the range, but I have not paid too much attention in the last couple years (other than using them ). I no longer have the helper springs as they were removed to allow the car to get really low.

[Bill Verburg]

What are you guys running for ride heights?

Interesting about the helper spring positioning, these came off a 993, I believe that VB did the install when he was a Ca. resident.

The straight drop link worked w/ TRG bars, but not in all positions.

Your front camber plates appear to be different as well.

[Tom W]

Bill: I'm off to Sears Point in a few minutes. I'll take some pictures and real measurements while there.

My 3.25" clearance jack will not fit under the jack points on the car, so it's a bit low. As they have it setup, I do not have any significant issues with bump steer. It likes to dance a bit under heavy braking, but I think it's more toe related than bump steer.

[ted]

Originally posted by Bill Verburg
Interesting about the helper spring positioning, these came off a 993, I believe that VB did the install when he was a Ca. resident.

Are what you calling a helper spring the same thing as a spring tender?
Is it common to run coil overs with out spring tenders?

[Bill Verburg]

Yes

and

yes

[GT2R]

Bill,

The 993RS springs are too soft for track use. I would shoot for a higher spring rate than that.

For the GT2, what color Motorsport spring is your data referring too? In addition to several different colors (blue, yellow, purple,...) , you can add the Versa Spring to these springs which allows you to stiffen each Motorsport spring incrementally. If you have spring rate data for Motorsport springs by color, I would love to have it.

[Bill Verburg]

This is from the GT2 competition manual
non adjustable main springs front are *140-60-260 or 140-60-280 or 140-60-300 N/mm non color coded w/ a 40-60-30 helper
helper springs rear are 60-60-30 N/mm non color coded

The adjustable springs are 140-60-X so fronts and rears can be used interchangebly, each of these has 4 adjustments, I only included the lowest and highest in this table.

GT2	       N/mm    kg/mm	lb/in	N/mm	kg/mm	lb/in

front yellow	270	27.5	1542	320	32.6	1827

rear red	296	30.2	1690	350	35.7	1999

blue	        235	24.0	1342	286	29.2	1633

white	        284	29.0	1622	333	34.0	1901

I agree the RS springs are too soft the ? is use the 7/10 or 8/12 or buy another set 9 and 11 are also available and what combo to use. I am trying to get as much feedback as possible before I start tearing into this.

just ordered the curved rear drop links, and may have the bodies revalved as well( I know they are adjustable, but word is a revalve may be desirable anyway)

*length-coil diameter-spring rate N/mm

[GT2R]

Thanks for the data, I always wondered what the Motorsport blues were.

As far as choosing a spring rate, in my opinion, we always choose too soft. If the car is a track car, get at least the 8/12 setup. I am not familiar with the JIC hardware, but I would also look at the shocks compression and rebound.

Two weekends ago I got several laps in a 993 with PSS9, Pilot Sport Cups, and RS sways. The car did not have enough spring and had too little rear rebound. On the street it was fantastic. I guess there really is not compromise.

[Don Plumley]

Bill - Tom took me for a ride in the Turtle at Sears. You wouldn't be going wrong with the 8/12 if that is what he has.

I have the 8/12 in my somewhat lightened 993 - not that I pressed them at all, but the car was rock solid coming off the berms (also good sways).

[Tom W]

The inportant question with the PSS-9s is what they were set at.

I had a student running at Infineon yesterday with PSS-9s on his 993 and it sucked - but it was because his mechanic had them set at full soft. I showed him how to adjust them. I have PSS-9s on my 993 and agree that they are a bit more soft than you would want for a track only car.

I have the middle range JIC springs and think they are just fine for my driving.