mystert

The stock manual trans C2 91+ is 20mm. The RS sway bar is 18mm OD and 3 position adjustable. It looks that the stock 89-90 C4 sway bar is also 18mm. For a car that's only driven on the street (not worried about adjustability for changing track conditions), would this be a good lower cost option when paired with a 24mm front bar from H&R or a RS? Car is lowered with Bilstein HD and red H&R turbo springs.

Steve Weiner-Rennsport Systems

The H&R bars represent an excellent, cost-effective bargain for your purposes. The bushings don't seem to last as long as factory ones used with the RS bars, but they are not expensive to replace from time to time.

mystert

I wasn't worried so much about the front bar but the rear. I'm also not interested in adjustability because its a street car.


18mm 1990 C4 bar = 18mm RS bar ?

kreeshp

I've considered changing the sway bars on my C2 also but then I ask myself - what is the car doing now (running stock sway bars but on lowered suspension) that I want to change? If yours is a street car (like mine is), what is lacking that you feel the need to change the rear sway bar only?

I can't imagine driving the car even 9/10ths on the street.

mystert

I'm upgrading the front to the 24mm H&R bar and would rather spend $100 on a used 18mm C4 bar than $350+ for a 18mm RS bar.

Earlydays

All C2/C4's (non-Tiptronic) had 20mm bars front and back, with the exception of the M030 Sport option which had a 22mm F bar. The RS had a 5-way 24mm F bar and a 3-way 18mm R bar.
All 964 Turbos had 21mm F and 22mm R bars.

mystert

According to PET, the 89 and 90 C4 came with 18mm rear bars. Later tiptronics had 19mm and manuals had 20mm. The RS had 18mm adjustable bars.

Earlydays

I stand corrected: I was looking in the Porsche 964 Technical Specs Book I have and it does not mention the 18mm rear bar in the early C4.

mystert

So with that said, it's under $200 new for the 18mm C4 bar and over $350 new for the 18mm adjustable RS bar. I'm assuming most of us don't track our cars so maybe it's a good alternative for those who don't need the adjustability?

Earlydays

Do you already have the 24mm F bar and are trying to replicate the RS set-up with an 18mm R bar?
I would agree, if you don't track, or autocross the car you don't need the adjustability.

mystert

Exactly

Spyerx

stiffer bars all around will tighten it up a bit.

I have adjustable bars on 2 of my cars and well, i don't adjust them. I tend to adjust my dampers to deal with push and rotation on track. One less variable to mess with :-)

no_car

i ended up getting both H&R adjuatable front and rear sway bars, i'm still in the process of figuring out suspension setting including sway bar stiffness, its great to have the option to adjust it, but i do agree after i set the suspension once to my liking. i will pretty much wont change them again..

mystert

I did a little more research on the sway-bar sizes and I am starting to think that the 18mm rear bar on any non-RS car is way undersized. From what I've learned there are essentially two ways to set up a car, thick sway bars and soft springs, or thin sway bars and hard springs. See the following thread for spring rates-


https://rennlist.com/forums/964-foru...ing-rates.html


The RS front springs are 250-308lbs and it uses a 24mm front bar. That spring rate is in upper range of most common street spec springs and is why the 24mm RS or H&R bar works so well on the front end.


The RS rear springs are a whopping 375-508lbs and it uses a 18mm rear bar. That spring rate is WAAAY higher than most of the advertised aftermarket springs and doesn't need a thicker bar to reduce roll, the hard springs do most that work. The only common aftermarket springs with close to that spring rate are the PSS9's and H&R Super Cups. If your using one of the common street spec springs with a much lower spring rate you need a thicker bar. That must be why H&R offers a 26mm rear bar instead of the stock RS size.


I've seen many threads on here singing the praises of the RS rear bar but if you have any of the common street spec springs, your setup could probably benefit from a thicker bar than the RS.

cobalt

I am using H&R Supercup suspension (NLA) on my track car. Springs are 455 front and 685 rear with RS sways. It is a very nice relatively flat setup. I am running a similar setup slightly less stiff (don't hold me to it 250 F 450 R) not actual H&R parts on my C2 with TRG sways. IIRC they are 25mm front and 22mm rear 5 and 3 way adjustable. I found the TRG bars worked best with the rear at full soft and front at full stiff settings. So IMO the 22 mm rear at full soft is telling me that it is too much. Although it is a perfect setup on my car with the springs I have it offers me no adjustability.

Don't forget when you switch bars you will need to replace the drop links as well. It is cheaper to go with something from Tarrett for $275 front and $250 rear than buying the factory parts.