Jimjacqmx5

Dear Ninemeister,

Thanks for your very considered advice but I only mentioned once the $400 and only as a considered option if re- valving the shocks and fitting stiffer rear springs WOULD achieve what I needed and only considered this as several if the very quick cars are running this set up. I have stated several times that I am more than willing to spend $$ if better options are available.
Interestingly, the re-valve/rebuild tired shocks now looks like an $800 plus probably $400 for stiffer rear springs so a new set of KW CS coilovers for $3K is not such a bad spend.

Unkle

Can I ask a really dumb question? On a car that hasn't been corner balanced

Should the spring plates be even?
Or should the ride height be set on the datum points to your parameters e.g. RS +10mm even if this puts the spring platforms at greatly different heights.

Because if i get it right, the ride height being set correctly may require one or more springs to be preloaded a fair amount? which may throw out the corner weight? Is that the sum of it, or have i over simplified the issue?

I just checked the ride height on my car and it seems even height from side to side according to the datum points, but the spring plates aren't the same, with the driver side front and rear plates being higher up the threaded sleeve compared to the passengers side.

If i set it up for "fat git in the drivers seat" the drivers front and rear spring plate would be even more out in an attempt to get the car level for datum point measurements? Any side effect to this?



Sorry to hijack

NineMeister

When anyone comes into my shop and asks a question requiring a reduction in lap times, the first question I always ask is "How fast can you afford to go?" because unless the customer answers this honestly I would not be able to advise them how to get the maximum return for their money. The frustration you sense in my thread replies is that your original post asks about the gold standard for suspension which I have already answered on the assumption that you simply want the best possible solution irrespective of cost and already have wider than stock 17" or 18" wheels and suitable trackday tyres.

So, for without wishing to guild the lilly any further, my opinion (for what it is worth) is that you should lighten your car as much as possible, that the 60,000km Konis & springs are shot and you should forget about rebuilding them in preference to fitting the following according to whatever budget you have:
1. KW Clubsport set (or equivalent)
2. RS top mounts (or equivalent)
3. Front a-frame & rear trailing arm bushes
4. RS springplates
5. RS antiroll bars

Notice that at no time did I discuss ride quality, since your primary interest is lap time, however even with all of the above fitted your car will ride more acceptably than a stock 964RS due to the additional mass that it will be carrying relative to the suspension stiffness.

I hope this covers everything?

NineMeister

Before anyone gets the wrong end of the stick, by springplates you actually mean spring platforms, i.e. the adjuster screws on the struts and dampers as opposed to rear springplates on a pre-90 torsion bar 911 Carrera or SC.

So to answer your question, in my experience on new suspension (new springs & dampers) as a basic setting on assembly I would expect the spring perches to be evenly matched, however I would also expect minor adjustments to be made when you cornerweight the vehicle (either with or without driver) in order to get an even diagonal % split on the chassis. Differences of up to 3-5mm are not uncommon, however at 10mm I would suspect and look for a fundamental issue that could be causing the error - like a collapsed top mount or weak road spring.

DWS964

Perhaps this is a hijack, so my apologies, but seems relevant to the thread topic...
In terms of benefit:cost ratio is there a preference in the order of addition:
- swaybar upgrade (I have already moved to largest stock 21mm rear on my C4) to RS, TRG, H&R adjustable
- higher spring rates (currently on H&R Green, have Reds available, but should I go higher rate)
- upgraded bushes (beyond taking care of worn out original a-arm bushes, etc.)
- high-end shocks/coil overs (above/beyond the baseline Bilstein HD's)
For my case, the car remains a daily driver, perhaps becoming a less frequent daily drive, and occasional track toy.

Also, wrt to the options for stiffening up the rear (from advice for C4's to lessen understeer) in higher spring rates and stiffer rear sway bars, is there a "best" sway bar for the C4 application? RS, TRG, H&R, ...

Thanks for all of the great insight. I especially appreciate the "data driven" expertise out there.

Unkle

Yeah sorry i meant spring platforms

So spring platforms level side to side, even if this doesn't set the car to the correct ride height left to right? But if the level platforms give a datum point setting of 10mm out or more side to side, look for potential other issues.


Interesting, thanks

Jimjacqmx5

Thanks all,

Going through your list, what is the advantage of KW CS over Koni's with suitable poundage eibach race springs correctly valved? Not saying I don't want to spend the $ on the KW but trying to understand.
I have 24mm front and 22mm adj swaybars Plus a spare 18mm rear adj bar which I'd probably fit given the proposed doubling of rear spring rate from current 300ish to 600lbs.
I see you highly recommend the powerflex kit, RS spring plates and top mounts. I assume these three will tighten up the chassis. If stock bushes are in good condition, are these upgrades essential or will they give minimal improvement over swaybars and shocks with standard bushes.
I always thought some 'compliance' was not necessarily a bad thing?

Thank again.

NineMeister

Jimjac,
You need to look no further than the factory 964RS to decide whether the standard suspension bushes are up to the job of controling the suspension loading of a lightweight dual purpose road/track use 964. Then add 20 years of deterioration to the equation and I think you will come to the right answer.

As for Konis versus KW, the truth is that dampers have to be optimally matched to the spring that you are using, so it's not really a complete stab in the dark guess whether a revalved 60,000km shock is going to be up to the job or not. It would be different i you were having the dampers revalved for another 20-30K mls of road use, but when the purpose of the job is to go faster around the track just don't waste your time & money on something that will be a compromise from the get-go.

Jimjacqmx5

Awesome.
So plan is KW CS
Powerflex bush kit
Return to 18mm rear bar.
I believe the CS kit comes with new top mounts.

With set up, KW says the shocks are optimally set at factory?
They then have damping and rebound adjusting.
Any advice on settings or what does what?

Rioja del 73

3. Front a-frame & rear trailing arm bushes
4. RS springplates
5. RS antiroll bars

I hope this covers everything?[/QUOTE]

Thank you very much Colin for your explanations.
I am decided about the KW Clubsport and found them but have no idea where to purchase the other RS stuff and 993 RS hubs that you suggested. I am happy with my 964 calipers, can I still use them with 993 hubs and T-rodpackage?
Do you supply any of those to Spain?

Bill Verburg

Thank you very much Colin for your explanations.
I am decided about the KW Clubsport and found them but have no idea where to purchase the other RS stuff and 993 RS hubs that you suggested. I am happy with my 964 calipers, can I still use them with 993 hubs and T-rodpackage?
Do you supply any of those to Spain?[/QUOTE]

RS parts are purchased through any Porsche dealer parts dept.
993 RS wheel carriers will require RS outer tie rods and 993 rotors, you can't use 964 calipers w/ these, but can use either 993 or 993RS/tt calipers depending on which 993 rotors you use(304mm or 322mm) you will also want to use 993 rear calipers w/ either of the 993 fonts and also 993 m/c and booster.

Mondrian

Steve, Is this your track height? If so what setting do you use for Road, if different? Also how much weight loss do you have on stock 964?

Colin (or anyone for that matter), some prefer KW3 while others go for Bilstein - there isn't much in the price (unless I am looking at the wrong one) so I guess its just the feel that's different, how so?

Rioja del 73

I am already ordering the 993RS hubs and t-rod package and 993TT callipers but then...
front KW Clubsport should be for a 964 or 993?

Thank you all

boxsey911

My ride height (RS + 5mm) always stays the same. Changing it would probably be a pain and lead to messing it up. For prolonged road periods (the winter) I soften the bump and rebound on the shocks for more comfort.

Weight loss compared to stock...now there's a question! I'm lead to believe that the curb weight of a stock 964 C2 is supposed to be 1350Kg. However it seems unclear of what that should include. Full fuel tank? Sunroof? air con? Other fluids? etc?

On the scrutineer's scales at Oulton Park it last weighed 1305 Kg with 3/4 tank of fuel. Yet the significant weight reductions I've made are:

Removed all soundproofing
Removed undertray
Removed all aircon - compressor, hoses and radiator
Removed rear seats, deck and speakers
Removed rear wiper
Removed rear belts
Changed to light weight carpets
Changed to light weight door cards
Replaced heavy seats with lighter recaros

Along with a list of other minor stuff, the total loss has to be more than the 45Kg that my 'actual weight' versus 'stock weight' suggests. Therefore I guess that my stock car with 3/4 tank must have been quite a bit more than 1350 Kg...unfortunately, I never weighed it in its original configuration. The good news is that I've really felt the benefits of the reduced weight.

Mondrian

I thought the weight of the standard 964 C2 was 1375 kg but I might be wrong as it could be that this is for US spec cars, and that does not include options which on a fully loaded 996 can add 8% (no idea on 964). So if sunroof & electric seats were an option the extra weight would not have been included in the curb weight of 1375. Measurement should be according to DIN 70020 which is same for all cars (German DIN standard) - I know for sure it includes full fuel tank, spare & tools - not sure if there is any other additions as I do not have a copy of DIN 70020.

Mine is fairly standard but car has gone in storage for winter otherwise I would have weighed it so we'd know for sure.