max3.2

Hey,

I'm thinking about an upgrade on my swaybars since I'm changing my shocks and springs too.

Looking around I found so many different sizes and options. So i have some questions, I'd really appreciate any help you can give me...

First of all, whats the original specs in a 91 C2? Im not only looking for diameter, but also for stiffness values and lenght, or better the ratios between front and rear (well, assuming same material, they should be only diameter-dependant, but the effective lenght is interesting for the actual amount of drill)

Only changing one sway bar is not the right way I think. In my humble "fast-road-driving" experience, the 964 tends to understeer for a RWD.
But the infos I have already state a thicker swaybar front, so going up there will increase understeer even more, right?

For example, HR offers 24 front and 26 back. This will change the ratio and increase the stiffness on both axis. This will give me more oversteer, but just the size change sounds pretty extreme to me, just the change in diameter is in fourth power in the stiffness. Assuming a 20mm front stock part thats about a 100% increase in stiffness for the front..
The back stock values i found are 18mm. Thats 330% increase. So just using the different swaybar sizes (HR for example) will change stiffness ratio (disregarding actual drill and materials) from (F/R) 1.52 to 0.7???? I must have a bad mistake in there. Thats just a lot! I know its just one part of the suspension but this should move the car to oversteer pretty good.

Since i haven't found a sway bar thread, maybe we can start a little discussion. I have no experience on the car itself, but at least I'm an engineer but nothing is better than some serious experience and testing.
If there is already something like this, please just point me there i wasnt able to find it.

race911

What spring/shock package? Who you're working with on that will be experienced enough to point you in the correct direction. In any case, you don't want to introduce too many changes at one time.

max3.2

Im changing from stock to bilstein HD and red HR springs for a first try.

Im working pretty much alone but Ive got some experience, not with porsche thou. my main problem is getting my stock setup. i know thats just good for a very first try, but i'd like to know from where i start.
i have worked with some friends racing subaru wrx and this kind of cars. but those are front engine awd so a complete different chapter. but i can tell what to change when im driving. thats what im working with

i talked to jeff about the HR - he said thats wayyyyy to much. thats what i was thinking, but why do they offer them to "improve handling from stock" (found them advertised like that)? i imaging those tuning kids messing up their whole car, a change like this can get dangerous (in my opinion)
but those are the only ones i can really find. pelican only has them rs parts for 92?? do they fit?

Vandit

I know the H&R sways were mentioned in the "Orange 964" thread and the owner said he installed them but later removed the rear bar for a different bar because the 26mm rear bar was dominating the rear too much. What exactly that means, I'm not sure.

Does anyone on here run H&R sways?

Steve Weiner-Rennsport Systems

We have them on some dedicated track & race cars.

ThomasC2

The stock rear bar is 20 mm. The adjustable, three settings, Cup bar is 18 mm.

Thomas

boxsey911

The general rule of thumb is to make a front axle understeer you stiffen a suspension component and to make it oversteer you soften a suspension component. You do the reverse on the rear axle. There is a useful table about this about half way down the page of this 964RS website:

http://carrerars.wordpress.com/

To find the set up you really like I would suggest that adjustable sway bars is the best way to go.

freedman

Ive got them and like them, running standard shocks and lowered springs

Big improvement, on my C4 at least

timtim

Very interresting thread... I am looking around for more than a year now - to find a serious setup for my sway bars.
A freind of mine who is really fast on track has had the H&R (24&26mm) and the car became quite nervous in critical situations. He changed back to the original RS Sway Bars and is more than happy now. The problem is, the RS bars are not deliverable in germany for the moment... so if you find some - go for it!!!!

Cheers Tim

ThomasC2

I think the H&R rear sway could be a better option for the C4 were you most often want more oversteer. On a C2 I think the factory got it right when they put on a thinner sway on the cup cars to get less oversteer and more traction. I think it was a big improvement to move from the stock sway to the cup sways. So going the other way and put on a 26 mm in the rear sounds really strange, but I really can't tell beacuse I haven'nt driven a car with the H&R sways.

Thomas

KaiB

FWIW I run HR sways (both at first hole). This season with the PSS10s, low car, slicks and aggressive set up...I wouldn't have changed a thing. Push occured in low speed corner entry, but could be easily countered with trail brake.

Mid corner and exit push at higher speeds was easily countered with either a left foot on the brake or a lift of the throttle to set the nose - and then throttle down to catch it.

With the new MCS suspension going in, we have decided to retain the HR sways.

ThomasC2

And your comment Kai shows another thing that we often miss out in our discussions. A chassie set up is a subjective thing. What suits one guy and his driving style could be horrible for someone else. Slicks or not is also a big factor. So there's no right or wrong in this, just find a set up that you like and feel comfortable with!

Thomas

KaiB

This is so exactly true that it should be posted ten times a day!

All of this is a system, from the tire patch up through the driver's feet and hands (and mind)...no single component should be isolated without a thought to how it will affect the rest of the system.

I like a bit of mid to end corner push at my current level - a dear friend and very fast racer does not and prefers a looser car. The springs Steve chooses for my setup will not be the springs he chooses for yours. Pickles and oranges.

But it's all good, and all fun!

FeralComprehension

Let's start from first principles. As I understand it, a swaybar setup serves two purposes: 1. To reduce roll in turns, 2. To adjust the front/rear grip balance.

Unless you're buying a fully integrated setup from a known-good supplier you really have no way of knowing how much of either you'll need until after you've driven on your new springs, so unless you want to wait to mess with your bars you need an adjustable bar setup. Additionally, unless you want to actually r&r bars for tuning #2, you'll need an adjustable setup. So make sure whatever you buy is adjustable!

It seems like the common strategy to overcome the engineered-in understeer that these cars have is to add a bigger rear bar. It works, but I don't think it's really optimal to do it this way, since a stiffer rear bar reduces rear grip, thereby promoting oversteer. Unless you need to reduce roll, wouldn't it be better to use less front bar, adding grip at that end and thereby reducing understeer?

IMO you want to use the least-stiff bar setup that will work for you; a stiff bar by its very design not only reduces the amount of grip available at the target end, it also reduces the independence of your suspension by adding spring rate on bumps which only affect one side of the car. This is not desirable, but it's inevitable, and lower-rate bars are better than higher in this regard.

I've considered just pulling the front bar off my 'C4 to see how that works. I don't race, so I don't think the additional roll I'd get would bug me too much, and removing the bar completely is far less expensive (not to mention lighter!) than adding adjustable bars. Worked great on my turbo Miata with springs that were ~3x the stock rate.

$0.03
FC

Nader Fotouhi

We have Bilstein HD+reds on a 93 C2 that is/was used for DEs. I asked many questions about sway bar sizes and found many answers. The major effect on grip are the shocks andsprings. Sways only allow fine adjustments after getting the shock/springs set.

One thing I did not like about the H&R sway was that the fronts are larger than rears which will not help the understeer on a C2. Given that Bilstein HD does not allow adjustment except ride height, I ended up using front H&R and rear 22 mm TRG with Tarret drop links. You will not set the fastest laps, but the car seems to be a lot more predictable with this combination and agressive track alignmnet.