TRAKCAR

We will know Friday.

996CAB

Waking this thread up as what Paul has achieved with his PASM and now venturing in to spring rates mirrors what I have achieved with the Audi MagneRide...I ultimately found out that the stock dampers are good enough for all but ***** out competition/racing...the area to concentrate on is spring rates... double or triple stacking where possible...

...thus the combo of progressive tender springs stacked on main springs is a good example of how to get the 'softest' soft ride for street driving and 'hardest' hard ride for track use...

just my 2 cents...

Mvez

OR you can just install a moderate linear rate in the rear, like I did. The street ride of a Swift 672# linear rear spring is perfectly fine. Use a bigger rear bar to stiffen up the rear for the track, but this moderate rear rate is still great for bumpy tracks and street driving. This negates the need to "double stack" with a progressive spring, and avoid a damper revalve.

996CAB

Yes that makes sense too...thus paying attention to the the spring rates pays more dividence in what is being aimed for.

996CAB

...Paul,
I disagree with your calculations in red text using the above formulae.

Can you explain how you got to those numbers? I think you have used the formulae wrong...
(Main Rate x Tender) / (Main Rate + Tender Rate)
(900 x 250)/(900+250)
= 195#.

Nick Wong

Paul-

I have a question for you.

Have you experienced "ice mode" on your car previously, at a track with ripple bumps in the brake zones, and if so, did installing your revalved shocks and higher rate main springs w/substantial tender springs help reduce or eliminate that issue?

M3EvoBR

Usually 'Ice mode' has to do with the speed sensors on the wheels, reading different diameters or a different delta (than OEM) between front and rear.

M3EvoBR

sorry not on the wheels, but for individual readings.

Nick Wong

Understood, but perhaps ice mode intervenes when the suspension's high speed valving can't keep up with road surface oscillations. Happened to my car at Autobahn CC on the south track with stock shocks on "sport" setting.

M3EvoBR

on a bumpy surface, is more like the ABS working and not braking the car, happened to me a few times, but not at the track, it pushes your foot back up. Is it what you experienced.

obsessedone

Doubt if Paul wll note a change in that. "Ice mode" is not uncommon in cars with highly modified suspensions such as aftermarket Moton or JRZ suspension setups, seems to be more related to heavy late braking entering a corner. The few times I have experienced it with my Moton suspension with 750/900 springs have always been after taking a passes at the end of a high speed straight, e.g. turn 1 at the Glen.

997gt3north

I have a lot of experience with different ice-modes - one time it was costly - I posted about this a while ago. There are also lots of threads on this - I have commented in them quite a bit. I don't have enough days on the car to have any conclusion about if things are better or worse with the re-valve. I have learned to drive around the ABS issues that I know exist on various corner entry situations - i.e. I know my local tracks and know where it happens. The disastrous No-Brake and you are going into a wall Ice-Mode - I hope not to experience again - and I think I have enough experience in the car to recognize all the things that trigger it and I give myself enough escape room. I will say, that I would never race this car with the stock ABS unit as if you did it enough - you would lose your car for sure.

The ripple-bumps you mentioned is one of the classics - and it was the first ice-mode type that I found with the car. I found it at my first DE with the car and probably on the second lap. It was on the old Limerock - on the back straight coming into the brake zone in April 2007 with Porsche NJ Region DE. It just so happened that on that day there were 3 of us with new 997gt3s - and every single driver was commenting about how far offline they had to brake to avoid floating through the brake zone entirely. And, I had just finished a 3 day Skippy race school in the open wheel cars at Limerock and of course with no ABS never knew this area of the track had any issues. So, I learned my lesson day 1 with the car - don't brake over bumps - the car won't stop.

Concerning high speed compression damping and this fixing the problem. There is a post somewhere in the Racing and DE section about this specifically and mentioning Limerock I believe. Basically, with an expensive after market 4-way adjustable suspension, I think it was a guy named Larry, that was able to with a few turns of one of the ***** able to almost fix the problem with a still OE ABS unit - i.e. he found the right setup so that the bumps could be absorbed without causing an ABS heart attack. I'm sure this may have compromised other corners, but as it sounds like you already know with experience, if you can fix this ABS issue on bumpy track brake zones , not only will the car be safer - it can also be much faster.

If I had to guess, I would say that my re-valve has not fixed in anyway this issue as it was just in many ways scaling up valving to work with the higher spring rates - you are not able to adjust high and low speed bump and rebound until you find the setup that fixes a bumpy brake zone.

And, there are other Ice-Modes that no suspension turning is going to fix - namely what I think is the really dangerous one - it is related but different - it is the change in load on the rear axle Ice-Mode (i.e. braking and then lets say the braze zone goes 'more' downhill). This is the one that you can start with a certain braking force and then the computer can decide to give you 'less' force - and if you get it really, really, really wrong and combine a few more no-nos together, (A Pedal Stab, a perfect Pedal Stab just as the car hits a tiny bump and the rear axle load also changes) -> now you can get the Insta High Hard Brake Pedal with almost Zero Brakes - That's the Oh Fvck Ice-Mode. If you phone a few race shops that have prepped and campaigned custom cars with gutted 997s (non GT3s mostly) - they can tell you horror stories of customer's cars flying off racetracks at certain corners. This issue has been debated and discussed endlessly in the ABS threads - if you want to go racing, get a race car equipped with a Motorsport ABS module. I have also stated that if this was an easier and seamless swap (OE ABS Module out Motorsport Unit In for less than $5k) I would have done it long ago.

997gt3north

Turn 1 at WG is a classic - I get it every time there. Also downhill into 6 if I'm pushing it - and that is the lump in your throat one unlike in 1 where there is so much room to adjust your line.

997gt3north

I realize I didn't address this issue and I forgot that this post was originally about a potential Tender Spring setup specifically for bumpy tracks.

My above answers are for my own Re-valve with 600/900 pound springs.

Now, if you tried the potential Tender Spring setup I mentioned where the car would be riding on the softer / lower rate Tender Springs until more load brought the Mains into Play with OE non re-valved dampeners then I do think it would be better than higher spring rate setup. Porsche's own documentation and experience here says that on many tracks the Softer OE (non Sport Mode) setup is faster as it doesn't throw excessive damping at the shocks to 'simulate' a firmer ride. I will say that since I had Bilstein valve my shocks to work with my actually chosen spring rates (620,900) the valving is excellent in the OE non-sport position. Whereas the Stock car's 2 Modes are 'probably' (Slightly Under valved, Slightly Over Valved) or (Better on the Street for Comfort, Better on Smooth Tracks), my setup is now (properly valved for 620/900 rates, slightly 'over' valved for those rates) - it is a subtle difference but I will say with 100% confidence that the my car's balance feels exceptional in 'Regular' Mode - not under or over but perfectly spot on for the new spring rates. The 'Firm' mode tightens things up (just like it does with OE)

Finally, since I haven't personally tried my GT3 with my proposed Sebring setup - it would just be a guess - and that is why I pointed people to Posts where people have done this with other Porsche models - and claim good results.

My setup currently has 45# helpers in the front that compress under 90#s and 165#s Tenders in the rear that compress with 265#s. My research, and as Porsche delivered from the Factory, pointed me in the direction the Front of a 911 likes a Linear spring / Helper if required for Spring control (thus my choice of much lower spring rate) but the Rear of a 911 (as delivered from Porsche) does benefit from a higher rate Tender setup. As I said, I'm currently using a 165# rate that compresses with 265#s of Load (unsprung rear corner weight is 800-850#s on my car) so Tender comes into play when approx 550#s has been unloaded per corner. I have many other Tenders that I plan on trying next year that will support substantially more of the car's weight and thus come into play more often - but I want to test out the current setup first. Right now my tenders support 700#s of the cars 3140# weight (fueled without me) - a setup that I will eventually try next year will have the Tenders supporting 1960#s (364# each front wheel, 617# each rear wheel).

Nick Wong

Paul, thank you for your thorough answer. I have several thoughts on this particular topic but they aren't very relevant for this thread and I've already derailed it somewhat.