Interesting. I've had gmg springs on for ~40,000 miles...zero issues with premature wear, maybe I don't drive it enough.

 

Hi Paul,

1. I can't speak for 996TT, but for 997TT, the range is clearly given:
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https://www.6speedonline.com/forums/...-turbo-13.html
FYI and one more important piece of info: For the Turbo, Bilstein's official recommendation is that ride heights be reduced 10mm-30 mm in the front, and 5mm-25mm in the rear. That is, they actually recommend that you do not use stock ride height, and that at least you should try to lower 5mm.
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2. The lowering of the GMG spring is 24mm (1 inch).

3. I am hesitant to talk about lowering springs anymore since I don't want to upset anyone, but to answer your question: Yes, outside of some user's very positive experience with the GMG springs (and I don't dispute this at all), most definitely lowering springs are associated with higher rate of damper failure. To put things in perspective, failure is seen in any mod, any coilover, Bilstein, KW, or for that matter, any suspension mod, but the key word is HIGHER. And it *has* happened to a few people with 997TT.

There are 2 explanations for this, most people pay attention to the first one, problem of matching of damping rate to spring, but not many speak of the second one, position of the piston rod:
1. Unlike the PSS10, the stock damper is not designed to operate at a lower position. When the car is lowered with lowering springs, you're are operating at a range where it is no longer within spec as far as damping force. The piston sits lower within the coilover, where it's not supposed to sit. Published damping forces no longer are accurate at this lower range (damping force is given for a given range of ride height).
2. Unlike the PSS10, the stock damper is not designed to take higher spring force. As explained to me, the problem is in the rebound portion (extreme case: airborne or almost so), where the damper is exposed to the higher spring rate. This underdamping, besides causing wear and tear on the damper, is a very well known problem with lowering springs (google underdamped lowering springs) and is the source of "floating sensation" or sense of instability, that some members have reported here with some lowering springs (none so far with GMG). People would complain of "porpoise" motion problem.\

I am aware that an argument has been put forth in the past, that a PASM shock (like the stock) is somehow more lowering spring friendly; I have not found any expert who would agree with this at all.

In the end, I think that lowering springs do work (one of my forum advisor :-) here, "eclou", used Techart spring before switching to Bilstein), and you just have to be prepared for any problem, whether Bilstein, or KW, or lowering springs, once one starts modding the stock car. To use stiff lowering springs (GMG and Techart, NOT H&R - rumored to be softer than stock) is better than not to do anything at all.

 

GMGs lower by 20mm, exactly. At least on my car, I'm sure Fab will chyme in.....
Don't worry, I don't upset easy. All I know is that my car is consistently faster around the track (WGI, NJMSP,LRP,Poc), (within a very slight deviation) with gmg springs vs bilsteins.

 

Another point of data the RUF springs, made by H&R , lower the car 25mm/1". They are a fairly stiff spring, I would put them between the Champion (also H&R) and your GMGs. I will say that the springs with the toe arms and a GT2 alignment feels quite good, I hope to get it on the track soon and compare it to my Bilsteins. If it's not good my next step will be straight to Motons.
The 993s came equipped with a Monroe damper, they were known to fail with lowering springs in the day. The hot upgrade used to be H&R springs and Bilstein HD dampers. I haven't seen a failure of an oem Bilstein damper with a lowering spring on a 996 or 997, I could be wrong, if someone has specific examples please share them.

 

The GMG set up is a well reviewed stand out product definately worthy of consideration....as is the TPC set up. The "consistent" user reviews say it all. Maybe the rate of the GMG lowering springs negate the shock stroking 25 mm out of its designated spot better than other lowering springs....i don't know. Needless to say i would go with a GMG set before an out of the box bilstein coilover setup anyday. No offense Can but i've done the bilstein trip and out of the box they are just too unresolved in most driving situations, imho. Spending that kind of money just to get a lower look at the expense of compromising drivability and livability no longer does it for me. I'm over that ****. I'm sure whatever TPC have done with the Billys has made them into something which in reality they should have been in the first place out of the box.. So nuff said on that. Those guys at TPC have evidently gone out and done what Bilstein should have done for the car in the first instance so at best the product was a work in progress when it left the factory. And the evidence of the ongoing complaints and criticisms whether associated to incorrect installation, bought about by poor instruction or whatever is all there as evidence the product is half done out of the box. Not something i would care to personally stick on my expensive toy but each to his own on that.

That i would believe Chris. If the car has a resolved feeling in the way it rides then that in itself inspires confidence when pushing hard and fast into corners on a track...or a country road....and thats what you need and, want. Especially on a car like a PT. As you say your car, although only slightly faster probably does it with lower stress levels too (plus keeping your fillings in your teeth). A good performance suspension still has to soak up any surface irregularities without throwing the car off centre all the time in the process. I didn't get that feeling from the bilstein coil overs unless the track was billiard table perfect....and even then...there were moments. Other than full bore down the (smooth surfaced) straights that is.

And how many roads and tracks are smooth perfect everywhere like that?....hmmm,..very few.

 

So Doug. What do you have on your car/what have you had on your car? Am i right to assume you HAD Bilsteins and they are now off?....if so why if you don't mind elaborating....not that im having to guess too much And Motons? How do they ride? Have you considered the GMG set up?

 

I just want to leave my experience. When i bought the car i felt it very good for DD but every time i rode a bit more agressive (hard on brake, turns, hard on throttle) the car didn't respond like a 911turbo should do. There was too much body roll. I made a trackday in stock form and the overall was okay but i felt that it was a huge potencial hidden for such a car.

After that, i bought lowering springs. Once this car rarely go to tracks, i didn't felt the need to spend the extra cash for coilovers and waste time in the quest of the ultimate suspension tune (height vs damping).
The only options for me on springs is Eibach or H&R. Even most tunners springs is made by these companies, but with different rates and sometimes they only change its color and price. As eibach it lowers more the front than the rear, i chose H&R because it lowers the front and rear in the same proportion than OE. The ride became stiffer but still pretty acceptable for a DD. After a couple of months it became more softer but is still a bit stiffer than OE.

With a new trackday coming in the same track, i decided in the last minute to buy H&R sways before the event. So the only difference by then it was the springs and sways because all the rest was the same: tires, brakes... All i can say is that it improved not only the top speed in +13mph (156mph) but also it lower the lap time in almost 8sec.

On the street the ride, as i said before, is a bit stiffer but i also feel it more safe to ride and more planted to the ground. If i needed a more friendly ride for a DD, then the 911 is a no option. For that, Porsche has the PTT or even the CTTS, besides the other brands like BMW M's, AMG's...

 

Thanks for chiming in on this tpms pressure thread tiago but prior to you opting for lowering springs and then sways did you ever contemplate fitting some gt3 LFCa's to get some more camber wound on and, have a really good alignment done. Im not saying for a second lowering springs and sways aren't a good idea as im currently entertaining the thought of doing sways and drops myself but if you haven't got a decent alignment set up you are missing out on a major improvement, even for a car with stock coils and sways. It really changes the game.

 

I'll send you a pm, I don't want this to turn into a Bilstein bashing thread, the majority of their products are excellent.

 

Paul, the way you carry out your very careful arguments, it doesn't bother me, even when we differ in our opinions. I think it's good that at least you decided against the stock springs -- this is my primary point -- they really are way too soft for the average sports drivers.

1. I believe you're on the right track anyway with stiffer lowering springs, but let me add that your report above is much (very much) different from the typical experience with Bilstein in the Turbo. You're very careful with every mod, pls consider emailing the multiple tuners on this forum and ask them if what I said above is not true (your experience is NOT typical). The questions are first, it's not a Turbo right? Second, there were other things done to that car besides just Bilstein? Your report is so different that I am thinking could the tuner have done something wrong, as good as he might have been? I respect your evalution but is it representative?

2. TPC vs. Bilstein stock? Careful about the comparison! TPC faster? Yes. Will I love it and do I want to try? Yes, yes, yes! But... it's NOT necessarily for eveyone. When you make a suspension stiffer, you would sacrifice comfort. The Bilstein system is designed with Porsche engineers as consultant (yes the same one who developed GT3, GT2 and the like), about as legit of a mod as could be. It could be made stiffer to be faster, but it might be the better choice for many who look for more comfort.

3. As I've mentioned in the past, IMHO it's not a good idea to count failure based on forum postings and rumors. While Bilstein is far from being perfect (I could name a few things), the instruction as I have posted is detailed and crytal clear and Bilstein should not be blamed for incompetent installers -- the number one problem as I have seen it. As far as the one or two reported failures (!!), which suspension system has not had failure? The ones that fail, how do you know driver didn't hit something on the road? It's far from being proven if Bilstein is any less reliable than any other coilover or suspension. There are many many happy Bilstein owners on this board than any other suspension setup -- they are the silent majority. Again, if you want to be complete in your research, email the different tuners to the right and see if what I wrote is not true.

Recently AWE and TPC submitted 2 Turbo for head to head comparison, with reputation, skills, $$$ on the line, what do the 2 have: One is Bilstein, the other modified Bilstein. Both had excellent reviews, the TPC with better tire (Toyo Roxes 888) seems to have a slight edge (got an absolute rave). My question here is: This is a system that's developed by pro, tested by pro, reviewed by pro to be outstanding, with proven time on the track to be outstanding, driven by someone here as daily driver in New York city. You've spent so much already, why cut the corners here? Why trust forum opinions of one or two amateur drivers (me included) over proven work, and third party professional review?
It is also true though that the GMG got a very good review from Excellence Magazine, so yes I think you're doing the right thing with GMG springs. If I go with lowering springs, the GMG setup would be my choice; I would get the whole package though not just the springs (rear upper and lower control arms, GMG sway bar, etc.). But.. as you already know of course, as you add things and components, the very idea of comfort that you are going after might go out the windows also.

Yes, the floaty, unstable, porpoise motion you sensed is classic of an underdamped system, seen with lowering springs. It's well documented and I did not pull it out of thin air. Just because anyone of us here doesn't feel it does not mean that it doesn't exist. It's too bad that the GMG car was not in the Excellence Mag shoot out against the AWE & TPC Turbo. (For that matter, it's also too bad that the Moton Turbo wasn't there either.) Head to head, I believe the difference will be seen.

 

The tpms pressure thread ended in suspension and that is why i posted. The alignment was done taken in consideration the upgrades and only after a few miles to allow to settle down the new parts. The result is that after a year the tires don't show any sinal of premature wear. It hasn't a agressive alignment because the car is mainly for street, but as said before, even with only this it handle outstanding at track. And it is all for now about suspension.

If some day i decide to take the things more serious at track, maybe i will consider a few upgrades. The nr.1 in my list will be 18" with r-compound full slicks and track pads. Only then i might consider other suspension upgrades. Keep in mind that the more upgrades for track, the worst will be for street.

Besides the performance, the look was enhanced 100x by being in a lower stance.

 

^^^^Tiago, ok for your to post, my lovely TPMS thread has been hopelessly past the point of thread-jack 20 posts ago, and I am guilty as charged.

For the record, for those who might be interested in the TPMS issue LOL:

I am not sure at all but I think I *might* have found a solution to this low pressure alarm: I have recently set my tire to "Winter" (even though they are not; they are Pirelli Corsa cup tires) and for whatever reason, -4 on the differential reading does NOT seem to trigger the alarm any more.
There might be an explanation why this works: Because Winter tire setting implies extreme low temp reading and therefore, extreme low pressure reading (Charles law for the chem major out there LOL), perhaps the engineers allow more tolerance of low pressure before alarm is triggered?

Again, the TPMS has got to be the most temperamental/*****y device in the Turbo, and therefore I am not sure at all if my observation is going to hold. This is just a "work in progress" report in case anyone wants to try.
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I think Paul is just looking for real world experiences of other members, that's all. I'm sure he's well aware of all the experts around here!
Paul, I would call Fab at GMG, he'll give you the straight scoop. I already pm'd you my settings/suggestions. Re the tpc system, very good but at that price point I'd go Motons.

 

"Again, the TPMS has got to be the most temperamental/*****y device in the Turbo, and therefore I am not sure at all if my observation is going to hold. This is just a "work in progress" report in case anyone wants to try. "

I'll agree with you on that, the TPMS in the Cayenne is even worse!

 

Yes I agree that the TPC suspension is a little pricy, but for Paul? Sky's the limit! Anyone from Australia who could afford the shocking price of a Turbo: I wouldn't worry about his budget. I really don't begrudge TPC: They put in the work, the car is superbly tuned, proven to be lightning fast where it counts (at the track), what else could you ask for?
I enjoy writing about TPC's work because I think more emphasis should be placed on aspects of the Turbo other than straightline speed, namely handling, steering, track times.

Kidding aside, regarding Moton: Great system no doubt. But all the tuners that I've spoken to about this has made it clear: Use Moton and kiss the car good-bye as a daily driver.
There is only one person I know who has used and reported Moton suspension in our Turbo: my forum friend (Mike/Got boost). His experience is consistent with the above: For the typical, average driver, a Moton Turbo is un-useable on the street. Mike ends up with KW, another coilover system that I would very highly recommend.
As explained to me, the reason is more than about spring rates, it's all the metal mounting components (vs. rubber bushing) used in the Moton. (Any expert here please correct me as needed.)