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If you ask 5 different people what spring rate is best you will get about 30 different answers. So I thought I would let the numbers speak and show the method to my madness.
All numbers unless otherwise stated will be in N/mm.
Base Carrera 24/48 This really is the definition of soft ****. If you have a base, you need to study this stuff and work out what you really need.
Carrera S/GTS 33/108
GT3 /RS 45/120
I am yet to find a different spring rate for GTS, so we will assume that it is the same as Carrera S. The Base of 24/48 is so far away from the norm I will ignore it, except to note that the rear is twice as stiff as the front. As soon as Porsche went to the S/GTS they basically more than doubled the rear rate.
I consider every 10 N/mm to be a full step. So they went one step on front and 6 steps on the rear. You see why Base is really under sprung? Ok lets focus on S/GTS which I will shorten to GTS as that's what I have and compare to GT3 and RS and New RS.
Porsche went 12 more front and Back from GTS to GT3. So basically a step up front and back. But lets look at the difference.
33/108 is Plus 75 for GTS
45/120 is also plus 75 for GT3 So remember Plus 75. I will come back to that.
Now if you track and do a lot of track days, most suspension companies will recommend 100/180. Whilst that is awesome for the track, it is too firm for street for me. (Note plus 80 There is a reason- cost) To get increments of 5 costs you double. So to just use what is available they say 100/180. (Remember the 75 above)
Enter the Brand new 991.2 GT3-RS at 100/160. That's stiff, but note the plus 60. This is also the rate advised by the older track junkies and Ohlins to upgrade the older GT3.
So what is the ultimate spring rate for the ultimate- no compromise car that does it all?
Tarmac races (Road races) usually don't go above 70 on the front. They need to soak up the bumps. It's not the best for hard trail braking for a dedicated track car which would have minimum of 100 up front.
So if your car is mainly street use but don't mind a firm ride, then you will want something close to 70 at front. Now tarmac cars can be a little unstable on the track, so depending on how much you track and how firm you can tolerate on the road, you can adjust from there.
So I do like to go to the track and I want stability and I want to get better at trail braking. So I went with 75 up front. I had to pay double for that. Small price to pay to customise exactly what I wanted.
Then remember that 75 separation of GTS and GT3? So I separated it by 75 to bring the rear to 150. So I bought 75/150. (About 425/850 in American speak) Now want to see something cool?
GT3 is 45/120 Just add 30 to front and 30 to rear and you get 75/150. GT3 plus 3 steps.
Remember Base the rear is double the front? Double my front of 75 and get the rear at 150.
Now remember the ultimate track setup at 100/180 deduct 30 from front and rear and you get 70/150 (They did not spend the double to have 105/180)
So I am Plus 30 from a GT3 and -30 from the Ultimate track weapon. I am bang smack in the middle anyway you look at it.
You can double it, you add 30 or take 30 or separate by 75. All roads lead to 75/150 is the ultimate all rounder spring rate. (Have I convinced you yet : )
I’m using Öhlins Road and track 70/120 and think it’s fantastic.
Hi Awrryan, That's initially what I was told for the ultimate Tarmac car. Road racer. However a couple of track guys said, when they tested that at the track, it felt a little unstable. So they recommended 70/130.
Also I don't want equal to GT3, I need all the advantage I can get at the Track.
I doubt at our level in these cars anyone would notice a 5 N/mm increment. It was more about the math and my OCD getting the 75 up front. Also the higher the front the better trail braking, but you will start to sacrifice street comfort.
It shows how soft the GTS and GT3 are in the front. You really do notice the pitch and dive. I can't get mine fitted until next week. The anticipation is killing me. I am having those springs mated to the Tractive coilovers.
Do do you know if there is a different in spring rates between cars with stock suspension and PASM.
The GT4 and 991.1 drivers complained about car being too soft up front. Can you include GT4 rates in your comparison as well.
That’s all interesting but the spring rates have to work with how the shock,is valved. Unless you know and can test shock dynamics this is all,out the window....it’s a package type of deal..can’t change 1 thing with out changing the other.
That’s all interesting but the spring rates have to work with how the shock,is valved. Unless you know and can test shock dynamics this is all,out the window....it’s a package type of deal..can’t change 1 thing with out changing the other.
That’s all interesting but the spring rates have to work with how the shock,is valved. Unless you know and can test shock dynamics this is all,out the window....it’s a package type of deal..can’t change 1 thing with out changing the other.
+1
I don't know what Porsche was thinking, but I wager the 991.2 Carrera is one of the best-handling street 911s it has ever made. I've driven 911s with wildly high spring rates that worked well on the street (Synergy 997 and 991 GT2 RS come to mind), but the key is the dampers. Just as it is in this case, I suspect. When my base Carrera goes over certain lumps and bumps, I am blown away by how tight and iron-fisted it is in the rear. Might be worth looking at the rear bar back there, as Porsche really plays with those. Would I want it stiffer for track work? Probably. But they make 911s for that...or I'd get a GTS and mod that. But I'd mod it carefully, as I really feel PAG nailed this generation of the Carrera. Whatever is gained for the track is gonna come at a real cost on the street unless someone is a genius on setup, and those folks are exceedingly rare—and even then will have a tough time matching or beating Weissach when it's really on its game. And it really was for the 991.2...last time I saw it get a chassis this right for enthusiasts was merely the best handling car it had produced up to that point: the 987.2 Boxster Spyder. In that case, they used the ARBs and rear spring rates in conjunction to stiffen and soften things...just as they have with the GT2 RS. It's a system, and YM(and preferences)MV...
Hi Awrryan, That's initially what I was told for the ultimate Tarmac car. Road racer. However a couple of track guys said, when they tested that at the track, it felt a little unstable. So they recommended 70/130.
Also I don't want equal to GT3, I need all the advantage I can get at the Track.
I doubt at our level in these cars anyone would notice a 5 N/mm increment. It was more about the math and my OCD getting the 75 up front. Also the higher the front the better trail braking, but you will start to sacrifice street comfort.
It shows how soft the GTS and GT3 are in the front. You really do notice the pitch and dive. I can't get mine fitted until next week. The anticipation is killing me. I am having those springs mated to the Tractive coilovers.
i’m definitely interested in hearing what you have to say once your coil overs are installed. I have yet to dial up the firmness in the shocks, but plan to do that at Sebring October 21-22. I was at Palm Beach a few weeks ago, did not feel any instability
That’s all interesting but the spring rates have to work with how the shock,is valved. Unless you know and can test shock dynamics this is all,out the window....it’s a package type of deal..can’t change 1 thing with out changing the other.
Originally Posted by 4pipes
+1 what he said^
I have upgraded to Tractive Coliovers. These are the custom springs to be fitted to my TRACTIVE COILOVERS. They are fully programmable. They have a much wider range than PASM. They can go a lot stiffer. You can fully customise maps. Track, Street, Wet weather, Wife in car etc. Its like COBB access port for suspension.
Shocks also have a range. So for those of you with S-PASM, you can go stiffer and still be within the valving range. These springs are well within the range of Tractive.
Tom from TPC sells both the DSC module and the Tractive coilovers. I'm not in USA, they have a distributor here. I got the DSC first, and whilst that made a nice difference, really stiffened up the shocks, to compensate for such soft springs, I want more now.
I don't know what Porsche was thinking, but I wager the 991.2 Carrera is one of the best-handling street 911s it has ever made. I've driven 911s with wildly high spring rates that worked well on the street (Synergy 997 and 991 GT2 RS come to mind), but the key is the dampers. Just as it is in this case, I suspect. When my base Carrera goes over certain lumps and bumps, I am blown away by how tight and iron-fisted it is in the rear. Might be worth looking at the rear bar back there, as Porsche really plays with those. Would I want it stiffer for track work? Probably. But they make 911s for that...or I'd get a GTS and mod that. But I'd mod it carefully, as I really feel PAG nailed this generation of the Carrera. Whatever is gained for the track is gonna come at a real cost on the street unless someone is a genius on setup, and those folks are exceedingly rare—and even then will have a tough time matching or beating Weissach when it's really on its game. And it really was for the 991.2...last time I saw it get a chassis this right for enthusiasts was merely the best handling car it had produced up to that point: the 987.2 Boxster Spyder. In that case, they used the ARBs and rear spring rates in conjunction to stiffen and soften things...just as they have with the GT2 RS. It's a system, and YM(and preferences)MV...
I do have a GTS and whilst it seemed awesome at first, I did start to notice when I pushed it, that the front is very soft. 75/150 is not crazy stiff at all. Most track guys would say its far too soft. As I said, I had to fight off all the recommendations to go 100/180. With the advanced valving of Tractive Coilovers that react 17x faster than PASM, and have a much broader range, you get the best of both worlds. So I never felt the need to go track Stiff. I still want to drive most days in the car and take it out to dinner. Don't quote me but I believe (i read somewhere) PASM range is 500-1500 whereas tractive is 500-2400. So it can go a lot stiffer. They make all sorts of custom maps for you to download.
PASM is just the start. Porsche did a great job of collecting all sorts of data that PASM does not fully use. Whereas the Tractive says, Thank you very much, I know exactly what to do with that data that Porsche already collected.
Stiffening the front shocks when you stand on the brakes. Stiffen one side of the car when turning in. It is PASM on Steroids. The guys that made it have PhD's LOL.
i’m definitely interested in hearing what you have to say once your coil overs are installed. I have yet to dial up the firmness in the shocks, but plan to do that at Sebring October 21-22. I was at Palm Beach a few weeks ago, did not feel any instability
Hi Awrryan, I think we need to put this in context. I am absolutely positive 70/120 would be a dream on the street and be more than enough on the track for 98% of the population. These guys are Pro race car drivers pushing the car at 10/10ths. At 7/10ths your car would be a sweet heart all day long. I just wanted a little more up my sleeve as I push harder and harder. But not that much difference between 70/120 and 75/150. I will need a really big front sway bar upgrade soon, before I push above 7/10's.
If this Tractive setup is as good as I believe it is, I can turn the front up full and the rear a little to make the car "FEEL"like 100/160 at the track and turn it down to "FEEL" 70/120 for the street.
I would say all spring companies make both Progressive and Linear springs. My Eibach as you can see from the pic are linear. Progressive springs look like a pig tail, they get wider as they wind. Whereas if you look at mine, they are the same 60mm diameter all the way. Progressive is for street only, for comfort. If you push a progressive spring on the track, it just falls over. Linear is superior for handling, progressive gives a soft spring the feel of sportiness, but was made for comfort.
09-18-2018, 09:47 PM
Spring Rates - What was Porsche thinking?
