Recommendations for spring rate - Track only 996 C2

Hello all, Background information... I began racing NASA Time Trials with my 01 C2 this year, and I was hoping to get some recommendations for suitable spring rates. The car is only track driven. Specs/setup: The car has a competition weight of 3175lbs (with me in it) H&R Street performance coilovers, GT3 swaybars (sway bar settings: full stiff front, full slack rear) 36.5% (F) and 63.5% (R) weight distribution Maxxis RC-1 tires (225/255) (getting to 34/35 hot pressures) The car is very tail-happy during braking and throttle on/off transitions, causing trail braking to be very difficult. I understand that's to some degree inherent with a rear-engine layout, but I also suspect the 210 lb/in (F) and 260 lb/in (R) spring rates in my H&R Street performance coilovers to be contributing significantly to this issue. I read a bunch of threads on the topic and have landed on Feal coilovers as my most likely choice given their price, compatibility with my classes' rules, and general recommendation from users. I recognize that the preferred spring rates for our cars have changed over time, some quoting 600/800 ... 800/1000... etc but I'd like to hear thoughts from folks who have been there, done that and have experience varying their spring rates so that I can get a more-proper setup under my car for next season. Any input is greatly appreciated.

Im running the gt3 ohlins at 600/800 and if i didnt like the car so much on the street i would go with the 1000/1200 springs and revalve. U may want to look at some other thinks too. U need a gt3 or similar adjustable sways and semisolid motor moints will really control the back end wiggle under acceleration. If u really want to spend money get a lsd for the trans as it will srraighten car up under decel and out of the corners. I suspect there is more then just spring rate causing your issues as u have to address all the stock part limitations

If you plan on going with Feal, I'd give them a call to see what they recommend. They know their system better than anybody and can provide suggestions on springs and adjustments to settings to get what you want out of it. Same can be said with Ohlin and Bilstein. Agree with DeJeeper, you will also need adjustable sway bars, a great LSD, good tires and tire pressure management, as well as a perfectly functioning brake system without sticking calipers. Not to mention proper alignment and corner balancing. All of which play into the characteristics you describe. Bottom line is that it takes years as part time drivers to learn how to balance the car on the track to get the most speed out of it. Seat time and good basic equipment you can rely on are a good starting point.

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Gents, I apologize... late night posting makes me forgetful. I installed GT3 swaybars recently on the car, which helped to reduce mid-corner oversteer quite a bit. The car is running Maxxis RC-1 tires (225/255 due to classing restraints) the rest of the suspension is stock. Drivetrain mounts are Function First semi-solid and their transmission mount insert as well. The car currently has an approximate 36.5% (F) and 63.5 (R) weight distribution after the last corner balancing but I have been playing with the ride height and will need to address it again. Regarding tire pressures, this past weekend I dropped cold pressures down to 25/25 and that improved stability as well, resulted in a 33/34 hot pressure. Just in case anyone wanted a visual representation of the problems I'm facing, here's a video from Chuckwalla this past weekend. Throughout the video, you'll see a lot of front-end dive during braking, which causes me to kind of "wiggle" the wheel back and forth trying not to loosen the rear of the car while initiating turn-in. Same can be said mid-corner to exit when I come on the throttle, rear end squats quite a bit and the front starts to push wide dramatically, causing a few instances of on/off/on throttle application. I know plenty of driver mods should be made, which I'm working on as well. You Tube

Holy crap.

Those are dinky tires, so yeah - no surprise it�s going to be a handful. You don�t mention what LSD you�re running, you need to put a guard or OS unit in if you don�t have one. My .02 - put a data logger in the car, it will be the best investment you can make in actually getting faster and give you a method to evaluate changes quantitatively. Data also pays off when comparing with buddies or giving to coaches for eval. As far as your question on rates, what you�re running seems to be to be junk. Where you go from there IMO is dependent on the damper capability. I don�t know anything about Feel, so not much to offer there. Fun ride along !

How do you have the sway bars and H&Rs set for stiffness front and rear? As an example my 02 is set to GT3 specs using Bilstein PSS9s, Tarret sway bars, Guard LSD, Brembo GT brake kit, with no aero. Wheels are carrera 2s. Tires were either hoosiers, proxies, sport cups and i will most likely go to Falken 660s next year. Stock 996s are prone to understeer so i wanted to correct for the front end pushing. In your case, you have the opposite issue. (After watching the video a few times, it looks like you have understeer then oversteer). Fwiw, here is my set up which may help jn thinking thru your next steps. PSS9 Rear is full stiff setting, Front is one click stiff above middle. Tarret sway bars are full stiff in the back and full soft in front. Took me two full track days with my indy at the track to get this setting right. This set up gave me excellent mechanical grip, solved the understeer problem and I never had an oversteer issue. While I was at the edge, I never went over. As a side note, the icing on the cake for stability was the LSD. Eliminated inside wheel spin when outside wheel is loaded. Also provided much needed balance and stability under side to side weight transfer, breaking and downshifting. Sure, tire temperature, stickiness and pressure plays a huge part. Obviously Feals, Ohlins, H&Rs all have different characteristics and issues to deal with in the set-up, but hopefully this helps a bit to think it thru.

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Looks fun, doesn't it? Thanks for sharing about your setup. Do you know what spring rates are on the PSS9's? On my car, the sway bars are set full stiff front, and full soft rear which is opposite of yours. I've heard multiple trains of thought about this, with some folks ditching the rear sway bar entirely. Surely one way must be more appropriate for our cars? Shrug. The H&Rs are non-adjustable. Unsure what exactly this is called but they have a "fixed-body design" where effectively any ride height change (lower collar adjustment) creates more spring preload. I bought these when the car was a DD and they worked well for street-only, but I'm thinking they need to go now. I spoke with H&R months ago about changing spring rates and keeping the dampers. I was informed I can raise the rate approximately 100 lbs/inch and still be within the limits for the dampers, but I don't think that's really going to get me within the range of appropriate spring rate for the car based on what I'm seeing.

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No doubt about the smallness of the tires, but I used to run R888Rs 235/295 and had very similar experience. If I had to say, I'd think it's a bit more stable now with the Maxxis and GT3 swaybar setup than it was with the R888R and stock bars. The car has an open differential, are those units you mentioned 2-way differentials? Regarding data logging, I agree it's very helpful. I usually have trackaddict on and working throughout the weekend, but it was giving me fits so I ditched it for that session. It's helpful and an extremely good value for how much it costs, but I am budgeting for a dedicated logger here soon. Leaning toward the AiM Solo 2.

OP - I’m not alluding to any experience but my own. I haven’t done any track, but auto-x yes, with my C2.2. I do have plenty of laps in several different cars and classes on track. To me, overslowing on entry kills a lap in a 996 C2. When I look at data traces, smooth entry with no lateral jostling, is definitely faster when all 4 wheels are at max contact patch (perhaps braking 5’ earlier). I’d rather let the rear drift just a smidge on exit and carry the extra 2 mph through apex as I start unwinding the steering and power back on. If I was experiencing the symptoms you describe, on a nearly stock C2, I’d look at: 1) Brake application rate. The stock system doesn’t like pedal jabbing. I have to start less firm/abruptly and then smoothly mash hard. My personal cue is, “In one more [fill in the blank]…” means brake now with my stock brakes. Plenty of good track pads out there, just gotta find the right one. 2) Brake release rate. I pop off the brake just a little early for fun, just to get the rear to wiggle (gets my kids to giggle). Stock set up, driven at the limits, will always be skittish for many equipment- and tire-related reasons. 3) Rear sway. Need at least a 3 hole. 4) Camber, toe and springs taken as a system. Already mentioned. 5) Stiffer poly transmission mount. 6) Cost/benefit ratio. What can I do to go faster without unreasonably endangering the motor? Am I at the point where an LSD will get me a 10th per corner? Do I need a better brake master, bigger discs, better pads? 7) What do the fast guys in my run groups do? You’re on the right path to success. Lots of smart track dudes on RL will give you great advice. My input for you to start next season? Feals with Swift, adjustable rear sway, a moderately aggressive alignment, poly transmission mount, GT3 front coffin. These items require minimal changes from stock. Address your braking approach as a system. For your technique, what combination of brake deceleration onset and pressure release characteristics will safely gain you the most? Nothing mentioned above will cause your M96 to detonate and are very cost effective. I’m wary of adjustable engine mounts. My experience on my M96 3.8 was I had high rpm cut out, probably due to anti-knock sensing when using Wevo mounts. Granted, my motor is higher torque than std 3.4/3.6 M96. I went back to stock Reins and have zero issues. Just my 2 bits… and just saw your video. Fighting a bit of understeer, huh? Fun times.

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Hatchet, I think there's a lot of great input there, thank you very much for the post. Over slowing is a problem I absolutely need to work on. I've developed some bad habits sim racing GT3 race cars in that, they have huge straight line speed compared to my car, and almost always require significant braking as a result. I haven't eyed-in super appropriate corner entry speed yet. Also, your mention of smooth entry without lateral disturbances is another area I need to improve on. As I get more experience with this car, I can tell that it really rewards you for being as settled as possible from initial braking to full-throttle on exit and conversely, punishes you if you stray outside of say (20%) "settled" during cornering. Regarding the GT3 coffins, is the primary benefit of those additional camber adjustment for the front? I've got Tarret engineering front mounts, and have the car currently set to -2.5 degree front and -2.7 degree rear. And yes... understeer and oversteer unfortunately. I know I'm doing my fair share to upset the car but it's rather wayward when you get to that 9/10ths mark. Was fun initially but after suffering my first spin in 3 years of track driving, I'm taking that as a sign fun time is over.

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Yup. You got it covered. Try driving your GT3 sim in 3rd and 4th gear around a sim track.

I gotta look thru my records to find the spring rates. Most likely standard springs rates that came on the coilovers specifically for the 996. Bought them thru FVD. If you are serious about tracking the car, I would at least spring for a set of Ohlins or Bilsteins. My PSS9s have performed extremely well and are still solid as hell after 14 years of tracking the car, so i will probably stay with Bilstein and move to the Bilstein club sport kit in another year or two. As much as I want a set of JRZs, I just don't want the costs and headaches of setting them up. I bet that someone here on RL runs your H&R set up and can provide guidance on how to sort it out. Please keep us posted, we love this stuff.

That camber is insufficient for a semi slick.

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I will give that a try and see what can be learned. Just to clarify, when I say GT3 I mean Cup Grand Touring Cars, the full-on factory race cars. Think Assetto Corsa Competitizone. 14 years sounds pretty amazing! I've never used Bilstein products before but that is certainly a great endorsement for them. The JRZ/Moton recommendation has come up in many other discussions, and I'm sure they're fantastic products. However, from what I've seen they're prohibitively expensive for me right now. I will absolutely keep this thread posted, I really appreciate all the suggestions received so far. I suspected that may have been the case. Maxxis recommends -4.2 and -3.0 for the spec E30 group (as they are they required tire for that group). In order to get closer to that, would adjustable lower control arms front and rear be required? As mentioned previously, I have the Tarret upper mounts, but I suspect they'll max my front camber around -3.0 at best.

I feel like I need to take a nap after watching the video. That was a workout! I like the tunability of my Feals. They're great for dual purpose vehicles, or for changes at the track. The price point is great compared to other options. But I might be tempted to run something else if I had a dedicated track car and a higher budget. Zbomb is correct, those are dinky tires! They're smaller than factory sizes.(At least what my 996.2 says are factory sizes)

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Be careful on this. FwIW, i am certainly not a suspension expert and only know what i learned from my indy over the years which supports the PCA DE and Club Racing community, but here us what I was told. For a 911 the general rule is that a stiff front and soft rear creates understeer. Conversely, a stiff rear and soft front creates oversteer. So to mitigate understeer and get the car to rotate thru the turns, most run a bias towards stiffer rears and softer fronts. However, It's a balancing act of trial and error to get it right depending on equipment and driver preference. Aero would add another layer of complexity.

You will likely want adjustable LCA in the front to get to recommend spec. Not needed in the rear but you will want adjustable toe arms to correct for the additional camber. Frankly, for what you are saying you want to do, especially with such a neutered tire, you want every upgrade allowable by rule. You can send stock arms off to elephant and have them install uniballs, or buy upgraded arms with uniballs. Remove as much weight as you can legally to lessen the load on the tire to the greatest extent you can. Look at the damper and spring as part of a system to include any compliance left in the system when you�re done AND remember that the stiffer the setup, regardless where that stiffness comes from be it chassis arms or spring, it all needs to make its way through the tire and an undersized tire will give up the ghost faster than a properly sized one. In my opinion, going too stiff or underdamped will exacerbate this issue. With the tire you�re running, you will not find a lot of input from people that have direct experience doing what you are, so a setup that is easy to evaluate and make incremental changes to will be advantageous. If I were you, I would build my setup off of the ohlins R&T, it is a proven track performer out of the box and will allow the tunability and availability of actual race experience support to maximize it. You really need to put a clutch type LSD in the car BTW.

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I definitely have broken a sweat a few times while trying to push the car! When you ordered your Feals, which ones did you go for? 401, 401+ etc? Also did you work with them on spring rate or did you take the default 6k/12k option? The tire size is definitely a challenge, but one that I'm hoping is not insurmountable. My 996.1 came with the sport designs wheel option (unsure but I believe they were 225/275) but the non-option cars came factory with 205/255 if I'm not mistaken. And this is what I've understood to be true as well. As the car has a lot of braking/turn-in instability at the moment, my brain says to bias the car toward understeer (in order to induce stability). However, I can also see that perhaps the car actually has too much understeer currently, causing me to compensate with weight transfer to the front and not balancing that transition very well, creating instability. Definitely solid advice here, and you're spot-on regarding building the car to the rules. I'm currently trying to get an exception to NASA's TT5 classing rule. The car fits in that class given it's current weight, power level, and tire size. However, it exceeds the factory-rated horsepower figure considerably. I'm waiting to hear back whether the exception will be granted... if it doesn't then I'll have some additional flexibility with more weight reduction and bigger tire. However, I would very much like to stay within TT5 if possible (which limits me to a 255 rear tire). Regarding uniballs, that is an option that I could potentially take but it means I have to run the car a bit heavier. I've removed about 175lbs out of the car as it is, and we can fairly easily go up in weight from there, but I have very limit room to remove more (maybe 50lbs) and be TT5 compliant. Interesting point about potentially having too stiff of a suspension for the given tire... I hadn't considered that. The Ohlins R&T is a stretch on the budget, but I would certainly consider it if it's a better fit. The only thing that concerns me regarding Ohlins is the service interval... I believe they call for servicing every 10-20 hours of road racing, which seems incredibly frequent.

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That's all correct. Sway bars transfer weight from one end of the car to the other. More accurately, from one corner of the car to the opposite corner. Stiffer rear = more weight transfer to the front = oversteer.

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Very interesting, I didn't realize it worked corner to corner. Makes perfect sense though.

U probably dont want to hear this but u should abondon this class. With the restriction of tire size, hp level and a rear engine car this is not where u want to be. Im not trying to be judgemental and i dont have a ton of racing experience but after watching that video, imho, u r putting yourself and possibly others in danger. It seams to me that u deffinately need less hp and more safety equipment with that tire set up. I wish u the best in finding a solution.

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that's amazing. have they ever been rebuilt? and how often?

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Never rebuilt. Car now has 59k miles on it. Put them on the car late 2006 or early 2007 at 25-30k miles on the odometer so they have approx 30k miles on them. Used the car for track and local street & hwy driving. No leaks, still working just fine. After a 5 year break from the track I tested them out in May at 80% lap speed and again at Road America in August. They still feel great. Quite frankly I am amazed at their durability being 16 years old. However, i don't know what they would be like if I put 80k street miles on them. But at least the seals are durable with age.

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No judgement felt... I'm not disagreeing with the thought that perhaps this tire combination is simply not workable with this chassis, that's possible. But I don't feel like the car is necessarily dangerous, or that I'm dangerous either (I don't believe you were saying that, but just to clarify). This was the first time I've been backwards on a track in 3 years of doing HPDE and time trial events. The car is definitely somewhat wayward and hard to control at the limit, which many of you have offered suggestions as to how to address that and I'm very grateful for it. I'm thinking we're collectively honing in on things I should be addressing, and I'd love to keep the conversation going especially regarding spring rates in order to better manage the weight transfer of the car.

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That's really impressive. I had a set of H&R Street performance coilovers on my Jetta (first track car) and they had around 80k street miles on them over 4-5 years and probably 400-500 track laps on them before I sold the car. They were going strong still.

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Yeah, my 996 was a daily driver from 2002-2006 on the oem suspension and then a street and track play toy since. Eventually the kids got to be too big and I had to get a sedan and then suv for the daily stuff. The bilsteins have seen over 1200 laps at Road America and many more at other tracks. Like I mentioned before, I'll probably replace them with a set of Bilstein Club Sports in a year or two. I like the low maintenence and durability of Bilstein.

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The club sports, what do they add over the PSS9s?

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PSS9s gave way to the 10s which added one more click of adjustability. The club sports have two way adjustability of 10 clicks each, more spring rate and more track focused, more set-up options. However, they can be used on the street as well. But it will be stiffer. Look at the clubsports as the next step without going 100% track while maintaining streetability. When I got the PSS9s, there was no such thing as PSS10s, Ohlins or Clubsports. The next step was a full JRZ/Moton track suspension which made no sense to me since I wanted to be able to street it as well.

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True that anti-roll bars/sway bars transfer weight between front and rear (when cornering) but a stiffer rear ARB transfers load from front axle to rear axle, not to the front as you wrote. That would increase understeer/reduce oversteer. Also it doesn't transfer it from one corner to the opposite, corner balancing does that. ARBs transfers load between F and R corner outside tyre. OP: Good deep dive on the subject given here: https://suspensionsecrets.co.uk/roll...d-roll-moment/

I’d try posting this video over on the racing and DE page. I’m terrible at analyzing video and don’t know the track, but it almost looks like you are to throttle early (way prior to apex) then rocking horse the car front to rear balance the rest of the way through the turn, fighting over and understeer with throttle. The pros over on the other page can provide valuable insight.

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Interesting, seems like I'll be taking a closer look at the Clubsports then. I'm going to take a look at that thread, because after reading your post, my brain hurts just a little. I appreciate that suggestion, I may post it over there and see what recommendations they've got.

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Don�t. They are $5K, no one runs them, you said the ohlins stretch the budget and they are $3190 and people actually use them. Gotta say, you have a lot of work to do, you�re not going to get answers to the detail you need here and it does not appear like you have researched very much on your own as far as what works in general. No one runs such a dumb tire. You�re trying to fit a round peg in a square hole with the class choice - pick a better class and have more people to lean on for help and learn on your own what historically has been shown to work.

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Just trying to take people's suggestions into consideration... let's not forget that my only goal with this thread was to gain some insight on what spring rates people are using for their track only 996s. Lots of other information has been put forth and that's great, I'm taking most of it into consideration. I have done some research when I first started tracking this car, and went with a 235/295 Toyo combination initially. It worked okay, then I switched from HPDE to Time Trial and am trying to maximize the car for a particular class. I am also learning as a driver (as I hope any of you who aren't Max Verstappen are as well) and know that I need to learn and adjust to the car. I spent the first half of the year driving the car with the Toyos, and then for the second half of this year I switched over the Maxxis and added swaybars. Now I'm adapting to the car as it is and trying to improve areas that I believe require some attention (the suspension). Here's the dilemma: Further evaluation of the rulebook shows I'm basically ineligible for TT5 unless I want to go back to factory weight AND get a national level exception, which won't happen. So this is moot. Let's say I decide to go into the next higher class (TT4). I'll need to drop additional weight, and realistically the car can pretty easily get to 3001lbs competition weight (that's including driver, and I weigh about 235lbs). At that weight. I'm limited to a 275 tire and I'm leaving almost 50 available horsepower on the table. I'm leaving the powertrain stock so, I'm significantly down on power compared to others. The next higher class (TT3) allows me to run an unlimited tire at any weight. Okay, great... Let's get insane with the weight loss with a 2800lb competition weight (significant cost and the car is destined to be a racecar forever) and run 255/305 Hosier R7s (much more expensive). In that scenario, I'm classed appropriately as my maximum horsepower given those parameters is 259 (which I'm just under when utilizing NASA's average HP calculations). There's a variety of other considerations to be made: cost to modify the car to fit into a particular class, running cost/availability of competitive tires and sizes for each class, wheels to run them, how many people actually race consistently in each class within my region (and thereby the availability of contingency money for each class)... it goes on and on. Up until about 6 hours ago, I was really hoping for TT5 because it checked more of the boxes than the other classes, however... that's not going to happen. If ultimately this car NEEDs huge tires to function properly on track, then it's simply not a good fit within NASA's classing structure and I'll probably sell the car and get something better suited. My reason for posting this thread was to discuss spring rates, as I've identified that it's likely the biggest single improvement I can make to the car (based on what I've felt with the car and read from others). Granted, spending the 3k+ to slap bigger/stickier tires on the car will probably result in faster lap times, but that'll likely just exacerbate the suspension concerns I have. Side note, I think the 225/255 setup has the potential to work fairly well. I understand it's not the norm with these cars, and that's fine. Guys/gals competing at the top level would probably never consider such a tire combination because they have the budget to build and race a car that NEEDs a much larger contact patch. However, I ran Laguna Seca about two months ago (with basically the same setup the car has now) and the car performed awesome. I think the banking found in most corners there helped alleviate weight transfer issues which masked my car's weakness. The only change I've made to the car since then is lowering the car 3/4" all the way around because the driver's front strut was maxed out on it "up" travel, causing a knocking over small bumps. The ride height adjustment I'm sure altered the corner balance I performed and changed the alignment slightly. I'm sure those items contributed to the struggles I was having in the first video I posted. You Tube

RubberDuckie, This is a good thread. At the end of the day it will help you to get your ducks lined up as you see fit. Two quick questions. 1. Do you do your own work or do you have an indy that knows their way around a 996? 2. Have you been to a PCA club race to see what the guys are running on their 996s, issues they have experienced and how they addressed them? While you got to make adjustments to your current set-up to mitigate the understeer/oversteer issues, at the end of the day yiu gotta figure out if you want (1) a street car that you can occasionally track, (2) a track focus car that you can street, or (3) a full time track car. That will tell you what you should do with your suspension set-up.

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you got it wrong. read the link you posted. stiffer rear ARB increases oversteer

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GC, I agree, I think there's a lot of good recommendations and discussions happening here. I don't want anyone to think I'm stubborn on the issue in any particular way... I just need to be very deliberate with the decisions I make from now on, I don't have the financial freedom to make a lot of "one step forward, two steps back" moves. For alignments and if the motor needs to come out of the car, I take it to a trusted shop. But besides that, I take care of it. And no, I haven't yet done that. The events that I've gone to show that 996's are a rarity. You'll see some much newer 911s but within NASA Arizona, I'm one of maybe two total that I've seen. I'll need to see when/where those events are coming up in the near future and pick their brains. Ultimately, we're approaching a **** or get off the pot moment with the car. I don't ever plan on street driving the car again, but I don't necessarily want to do things that will exclude the possibility of selling the car in the future to someone who will want to street drive it.

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I know it's easier said than done, but you have plenty of time to make decisions so you dont waste money, and you will if you make quick knee jerk decisions. Track isn't going anywhere. Get your current set-up sorted first. Then worry about the next suspension set-up once you have all the info you need to make a sound decision. Its easy to spend and waste stupid money. Personally hate to do it.

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That's very true, and something I need to remind myself of. Sound advice, thank you.

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OS Giken LSD All uniball with exception of rear LCA and tuning forks. Stock Ohlins R&T PN POZMI00 343/686 - Tire 245/305 PS4S and NT01 same size. Dual use track and street. Awesome on street and track. Car was very neutral on track until you got on gas too early then shift to understeer. More capability than I had experience for but my research said a rate bump would be dynamically beneficial, so I did it. 586/800 highest rate Ohlins suggested with stock valving. Principally track and car weighed about 3150 race weight. 245/305 NT01. Very good handling with big stability on entry allowing progressive trailbrake learning. Really started focusing on learning how to keep the V min up on this setup and because it was so predictable and easy to drive, it was a great platform to challenge myself without getting too far out of my comfort zone. This is when I started learning how well the car responded to trail braking and how you could minimize understeer by carrying more speed way later in the corner allowing the transition back to WOT to happen slightly later and allow a shorter maint throttle period before getting back to WOT. You have to really drive it into the corner, fun way to drive. 900/1100 - switch to JRZ 3 way. 275/305 NT01 car weighs 2980 race weight. Jury out on this, while I feel like the potential is far greater, reliability issues with the gearbox have meant not enough track time for satisfactory setup optimization (one man show). For now, I'll say the car has NOT been as easy to drive as it was before but has shown in certain sectors big gains and in others the potential for big gains when done right, but harder to do them right.

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Awesome feedback, this is the kind of information I was hoping to gain, thank you for that. I appreciate your sentiment regarding your JRZ setup having more potential, but harder to execute... I like the idea of a setup that's easier to work (learn) with as I know I have a long way to go with my driver development. With your R&T setup, what were your thoughts on it's combined rebound/compression adjustment? Did the increase in spring rate have any effect on how that performed? What kind of lifespan did you get from your R&T? Also, logically, my thought would be that (all things remaining constant) a heavier car requires a higher spring rate than a lighter car. Any thoughts on reducing spring rate as weight is taken out of the car?

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Simple. I was not in the habit of making a lot of adjustments. From memory when I had the softer springs I had the damper settings in the middle. When I went to the stiffer setup I ran the dampers toward the top of the range. I may have adjusted them once that season - it just worked really well and allowed me to worry about other stuff. I did not want something I needed to constantly tweak and, I didn't... and lap times kept dropping. 3 years, bunch of track days and they are on another members car now. I think the rebuild concern way overblown, especially for a car principally being used on track. The valving has a good spring rate window out of the box and a re-valve can shift that range to your needs. I would never run a damper for 5 years of principle track use without a rebuild, especially in a competitive setting where things have to work of you throw away all the prep, transport and entry fee money. Service your shocks - foolish not to. Don't know - I have looked to the cup cars for most of my process - they are very fast for what they are, they run big tires, big spring and low ride height - if you mix those ingredients in the right amounts, you will have a car that handles really well. As you can see from my progression, as my weight has dropped, rates have gone up.... see cup car explanation. I think for the cost of the Ohlins, the performance I saw and the support - I don't know why someone focused on an entry level track car would not choose them. I run in a small pond but I could drive the car to the track with them for a DE day, be one of the fastest cars on track and drive home, not turning a **** or touching the car the whole time, just driving - it was great.

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Thanks for sharing your experience. Good to hear they worked well for you. What drove your decision to change over to JRZs?

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Chicks dig remote reservoirs. And, for where I want to go, the advice I got was to make the jump and begin the learning process.

Since u wamt to know what equipement we have and how it works.... - 2000 c2 with the entire gt3 drivetraun, uprights and brakes - ohlin gt3 shocks at 600/800, would need to revalve to go stiffer - piggish 3400lbs with me in it -full uniball suspension with gt3 lowers, camber front and rear about 3.2, going to 3.8 front next season - gmg world cup sway, set full tight rear, 1 from tight front -nt-o1 tire 245f, 305 and 315 r I have about 35 track days over 2 years and about 3k street miles on this set up. I put the shocks at 10 from soft for the street and 7 from stuff in the front. The car had the potential to run with c5 and c6 zo6 cars and new cameros but im not that good yet. Also this doesnt have anything to do with my gt3 drivetrain or shocks because @hbdunn usually smokes me at the track on struts and a stick 3.4l motor

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I am not contradicting that stiffer rear ARB increases oversteer, but I admit I didn't write that explicitly. However, I contradict your explanation and wrote the correct explanation of how indeed a stiffer rear ARB increases oversteer. That's the point I was making but obviously failed to do so.

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Remote reservoirs are pretty neat. Thank you for sharing your setup. How would you describe the car in terms of it's handling characteristics?

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Its still a iittle tail happy thats why i was thinking about going stiffer on the springs. But after a couple instructors told me the car felt great and i should max out my driving skiil before changing the car im not doing anything to it this winter. i have learned that i can not toss the car left to right without letting the car settle in the middle, also the rumbles make it unstable sometimes. I have to remember that its a street car i drive on the track not a race car. If u want race car....u have to go full race car.

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This is the kind of information I was hoping for, thank you for sharing! Even with sway bars nearly full stiff front and rear, you're finding the left-right transition to be a bit tricky? Also tail-happy when, the most?

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most heavy left to rights. Uphill esses at watkins, transition out of the octipus at thunderbolt njmp, 7,8,9 transition at summit point main are just a few areas. Although i tried some pirelli slicks (scrubs) and the car was awesome on the summit tansition. these cars r real heavy behind the rear axle and they create a wag, u just have to learn to adjust your inputs and timing.

Started DEing my 996 in 2004 and it took me 4 seasons before I was able to figure out how to smooth out my inputs and more effectively balance the car thru transitions. I kept getting faster but as i did, i got to the point that everything felt on edge. In late 2006 I decided to go out again with an instructor as his passenger to watch and noticed how smooth his inputs were, how under controll the car was thru his transitions and how fast he was going without beating the heck out of his car. After that I decided to spend all of 2007 working on "smoother is better" by SLOWING down a bit and working on segments of the lap to smooth out the transitions. Braking, turn in, throttle, shifting, car positioning, trajectory and set up for the next turn. By the end of the season I gained quite a bit of speed but doing it with less wear and tear on the car. A good analogy is one you hear in sports which is you know you are in the "zone" when the game slows down for you. What ended up happening is that the smoother I got, the more everything slowed down on the track, but the faster I got. Driving on the track ended up becoming a rhythmic dance versus an explosive wrestling match. But no question, a solid suspension set up is a must.

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You two and many others I've seen are echoing what I'm learning is the reality of these chassis... they really reward you for keeping the car settled and can be very tricky at the limit. When I first started driving this car, I remember remarking about how stable and planted it felt. However, now that I've been adding pace to the car it seems the exact opposite. At 8/10 it's very manageable, 9/10 it becomes a real challenge to keep the car beneath you, and at 10/10 I don't have the skillset yet to string together more than a corner or two.

Now u r getting it . Combine that with an understanding on how each aspect of the car effects stability and u will get to a 10/10.

Thought I'd give a bit of an update to this thread. I posted a video from Chuckwalla last November, which really highlighted the issues I was having with the car. Since then, I've been racing NASA's TT5 class with a friend's BMW Z4. On the 911 front, I've been approaching the problem more deliberately than I typically do, focusing on adjusting one/two things at a time and getting some track time with it to see the effects. I hate working on cars during an event weekend (especially when I'm driving and instructing, there's just not enough time in the day). So, after Chuckwalla, I raised the ride height. Also, I adjusted the swaybars from (1 hole from full stiff front, 1 hole from full soft rear) to full stiff front, full soft rear. After the changes, I drove the car for a couple sessions at Radford's racing school track. The car wanted to understeer sometimes, oversteer others, just really inconsistent. Additionally, it absolutely obliterated both passenger side tire's outer edges. After seeing this (and knowing I jacked around with the ride height) I decided to make sure the alignment was where I wanted it. I borrowed a friend's scales and toe plates/alignment kit and got to work. I found the car had a lot of thrust angle (rear tires pointing toward the passenger side), cross-camber issues, and unequal toe in the front. Basically, it was super wonky. I don't recall measuring corner balance prior to the alignment, but I suspect it was also somewhat off. I installed a pair of adjustable rear toe arms that were donated by a friend (Thanks Keith!), raised the ride height another .3 - .4" and reset the alignment and corner balance from scratch. Here's what I ended up with (for reference, I'm 240lbs) : LF: Ride height (fender to ground): 625.5mm Weight: 630lbs Weight percentage: 20.0% Camber: -3.4 degrees Toe: 1/32" toe out RF: Ride height (fender to ground): 620.7mm Weight: 583lbs Weight percentage: 18.5% Camber: -3.35 degrees Toe: 1/32" toe out LR: Ride height (fender to ground): 631.8mm Weight: 979lbs Weight percentage: 31.1%$ Camber: -4.05 degrees Toe: 4/32" toe in RR: Ride height (fender to ground): 620.7mm Weight: 960lbs Weight percentage: 30.5% Camber: -3.85 degrees Toe: 4/32" toe in btw: I thought I saw some (Factory Porsche) information on ride height adjustment/ideal ride height... if anybody has something related to reference information on ride height, It would be much appreciated if you shared it. Once I had the alignment and corner balance where I wanted, the car waited until this past weekend to be driven again. Beyond the alignment changes, the only thing I did was switch from the Maxxis RC-1 tire to Kumho V730s. I have experience with both these tires on the Z4; the RC-1 has the superior pace, hands down. However, the V730 are much cheaper, last quite a bit longer, and actually seem to increase in pace as the tire wears for awhile. The new tire setup is 215/45/17 and 255/40/17. We raced this past weekend at INDE Motorsports Ranch with ProAuto Sports in their Hot Laps time trial series: You Tube We bested the old clockwise lap record by 1.2 seconds, and the counter-clockwise record (shown in the video) by just over 2 seconds. Needless to say, the car handled VASTLY better than it did the previous two times out. Overall, the grip level was reduced on the V730's when compared to RC-1 (to be expected) but the car was far more stable, responsive, and predictable. Small slides could be felt coming on very early, and countered with ease. The front of the car turned in very linearly and the limit of grip was communicated well and easy to find. Weight transfer is still an issue, but with the rear of the car being much more stable, small lifts of the throttle could be used to adjust the attitude of the car mid-corner when needed without having to battle a massive slide. Early throttle application can bring about some understeer, but line choice can mitigate that characteristic. Huge improvement over the past few outings. So far, the lesson learned is that alignment can play a huge part of how a car handles (duh!). Moreover, ride height changes (even small) can have big effects on the alignment. Always set ride height/corner balance the car FIRST then check alignment. I'm considering what the next move should be with the car. I still believe the spring rate is too soft, but I'm wondering if it's worth the effort (even just for the knowledge) to increase the spring rate with these street performance coilovers to their maximum rate, or assume the jump won't be enough to fool with, and just replace the entire units with feal/ohlins/etc. The ultimate goal with the car is to win a TT4 championship with NASA here in Arizona. Based off what I'm seeing from historic times at INDE, we're really not far off a winning pace at the moment. To stay compliant with TT4, the car can gain about 20hp, lose 175lbs along with adding aero, going back to the faster RC-1 tires, and a few other things.

Your alignment looks pretty good I'd say. I do not like toe-out in front as I find it makes the car much too darty so I run 0 front toe. I think a bit less rear toe-in helps with the turn-in myself so I run 3/32" each side. You'll have to see what your tires are telling you. Ride height is supposed to be measured to the diagonal arm inner bolt in front and to a tooling hole on the subframe in the back. These cars seem to like positive rake with the front lower than the rear. Measured at those spots I use 105mm front and 135mm rear. This works well with my suspension, it's worth checking the max settings for your suspension before committing to a particular ride height. Measured to those spots, factory ride heights are: GT3: Front 118mm, rear 133mm X73: Front 128mm, rear 133mm Row: Front 138mm, rear 153mm USA: Front 158mm, rear 163mm

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Excellent, thank you for that information! I'm assuming those measurements are intended for ride height without driver? I'm thinking those measurements are a good starting point, then adjust for corner balance from there.

Glad you are making progress. Link to a good reference book from Speed Secrets. https://speedsecrets.com/tune-car-handling/

I just corrected a rear axle alighnment issue. Found one side to be 3.5* and 2mm toe in, the other was 4.1* and 4 mm toe in, reset it to 3.3* and 2mm toe in. It was sooooo much better on the staights. I do perfer about 1.5mm toe out in front on my c2 chassis.

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Progress with this car feels quite good, hopefully I can keep the momentum going. I know we discussed Ross' stuff previously, but thank you for that link. And for anyone who hasn't gone into his materials, it's highly recommended.

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That seems to be what I'm running as well, right about 1/16" toe out in the front. The car felt just a little bit "darty" initially, but I quickly got used to it.

Here are the cup car ride height specs. And the alignment specs... Thought you may find interesting.

Great! Thank you for that information! Are those toe measurements given in degrees? Minutes of angle? I'm not familiar with the designation there.

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It says minutes. '

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Okay, thank you. I'm trying to convert MOA to something I can more easily understand... would you happen to know if MOA conversion to mm (in an alignment context) is dependent upon wheel (tire) diameter?

I dont know the conversion but it is dependant. I measure my toe at 19" apart. I have custom hub plates that i just had made and it makes it much easier then finding a flat surface on the wheel edge.

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Looks effective. Basically the same sort of thing I used... I believe it was a kit from Motive engineering.

Search 996 GT3 forum for Kussmaul settings. That's all you'll ever want/need to use.

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I will do that, thank you! Edit: is this it?: Vehicle Height Front axle height 115 + 5 mm (115 to 120 mm) Rear axle height 128 + 5 mm (128 to 133 mm) Wheel Alignment Front Axle Toe unpressed total +5’ Toe difference angle at 20� lock -1� 20’ � 30’ Camber (with wheels straight ahead) -2.5� � 5' Max. difference, left to right 5’ Caster 8� � 30' Max. difference, left to right 30’ Rear Axle Toe per wheel +17’ � 2' Max. difference, left to right 5' Camber -2.3� � 5' Max. difference, left to right 10' Do you have personal experience with it?. Looks like it's calling for 2.1ish mm of toe-in per rear wheel (About 4.2mm total rear toe-in) and about .5mm total toe-in for the front... which is a reduction of toe in the rear and an increase of toe in the front from what I'm running. In theory, that should make the rear a bit more lively and numb the front. Reduced negative camber as well. Interesting...