Kika

Ever since Gonzilla (Damn you!) let me drive his car, I got to thinking and doing some research on 993 sway bars.

There are a number of good threads on the topic, This is what I found:
Please correct if the numbers or assumptions are incorrect, I found all this info in previous threads and manufacturer websites. (don't shoot the messenger!)

Stock US C2 bars are:
Front: 20mm Rear: 17mm

Optional Bars include:
Front Rear
M030 22mm 20mm
993 RS 23mm 20mm (5 way and 3 way adjustable) ref: Van1 and ToSi
964 RS 24mm 18mm (5 way and 3 way adjustable) ref: ToSi
US Turbo 22mm 19mm
Euro Turbo 22 mm 21mm

Aftermarket
H&R 26mm 24mm (adjustable)
Tarrett 23.1mm 20.2mm (adjustable)
TRG 25mm 19/22mm (adjustable)

My car is primarily street drive, but I want good handling characteristics, but not a dedicated track beast.
Advice seems to be:

- Money no object: RS sways
- High Value: Euro TT sways
- Less aggressive maintain comfort : M030

- TRGs are very large bars, COULD/MIGHT interfere with other suspension components
- 1mm increase is about 20% stiffer (see post #3,ToSi below)
- Rear M030 bar may be made adjustable by drilling additional hole for 25% increase in stiffness (ref Tosi)

Questions:
- M030 and Turbo, both Euro and US have 22mm fronts; Are these actually the same bar? if not, what is the difference?
- Although Euro TT rear is 1mm larger rear than M030, I suspect for most of us street driver, the difference is inconceivable.

If I can find a set of Euro Turbo bars, that seems to be a great bolt on, otherwise, fall back to M030s.

Van1

I thought RS bars were 23mm front / 20mm rear.

For street driving I'd keep it simple and non adjustable. M030/RoW turbo is a good bang for the buck. I use a 22mm front M030 bar (original to car) and a RUF 21mm rear bar (probably same as RoW turbo or close). Combined with PSS10s I am satisfied with how it all works at the track.

Kika

I found a variety of sizes listed for the RS bars, Pelican lists them as 24 Front 18 Rear on their website.

ToSi

993RS is 23mm front / 20mm rear. The 24 / 18 sizes are from the 964RS.

Holding everything else constant, increasing the diameter by 1mm increases the stiffness of the bar by ~20%.

You can make the rear adjustable by drilling a new mounting hole further inboard (~25% stiffer). Be careful with drop links as this will add more load to them, ideally re-clock the mounting bracket & links so they are close to vertical at rest.

Haven't been able to find an answer - anyone know the hole spacing on the RS rear bar? Difficult to approximate from photos, looks like 15 to 20mm?

Photo below, 'adjustable' M030 20mm rear bar:

Kika

Thanks Van1 and ToSi, I will try to keep the initial post updated with the correct info for reference.

so: are the M030, and Turbo front bars, at 20mm in fact the same bars?

Cupcar

The expensive part of the RS kit is the drop links. The RS bar mounts under the control arm instead of above it as is standard so the links curve and the front are different as well.

The parts book shows the same part number for the Turbo and M030 front 22 mm bar 993.343.707.01

BTW, a 23 mm bar just clears the brake booster in my car. So beware of bars larger than this.

JMR

I ran TRG's with RS rear drop links for years without interfering with any suspension components.

Mark in Baltimore

+1. Have TRG's and love them. No clearance issues.

Kika

JMR, Mark,

thanks for the input, I think it was a Bill Verburg post that I read where he had some clearance issue with the TRG bars.
NOTE: Bill's car is heavily modified, and may not be representative of the average 993.

cgfen

Thank you for calling them Anti Roll Bars and not just sways....

FWIW
i tried the Euro Turbo ARBs and they worked fine with obviously diminished body roll, but they contributed to too harsh a ride, so I bought the 993 RS ARBs.
no complaints about these bars.

With a C4S you can use original front drop links and for the rear you must use non-stock RS-type drop links.

Craig

Cupcar

Answer = 15 mm

Bill Verburg

As Cupcar mentioned, the bigger front bars in a car w/ vacuum boosted brakes tend to rub on the vacuum can, I had that issue w/ the TRG bar and to a lesser extent w/ the RS bar

In front the RS drop link and stock have the same curved shape, the RS is just more robust.

In back it's best to use the curved RS or angled Tarret drop links when the bar is mounted below the transverse suspension links to use the softest setting.

jstyer

Bill, would the only solution to prevent the larger bars from rubbing on the vacuum system be to just switch out to the turbo/C4 system?

Bill Verburg

No that is a very involved project, the vac can can usually be adjusted a bit but the bigger the bar the more likely permanent rubbing will be.

JMO, the RS are thy biggest I'd want to use and even those are in the neutral holes, but that also depends on the spring rates, shocks and wheel/tire setups.

again JMO but stiffer springs and matching shocks w/ smaller(RS) sways are the way to go. You would be amazed and how well even the very heavy duty Cup springs do even on the street w/ matching digressive shocks. It's sort of difficult to compare but I swear that my car w/ 600/750# Cup springs/shocks rides as well as the setup it had when I bought the car which was full RoW M030, of course there there is much less wheel travel but on reasonably surfaced roads I don't have an issue, friends have the same sort of springs w/ Motons on their 993 dd's and report similar impressions

nile13

Kika, I think for the street car the bar choice will heavily depend on the rest of your suspension and width of the tires.

I've tried several combos and happen to like the current M030 bars on the car for street and autocross. The issue with stuffing the largest possible bar in the back (like 22/21 Euro TT combo) is that you making an already understeering setup understeer even more. Unless, that is, you've worked that issue out with springs and tires.