jskylarwilson

Hi All,

I just changed my suspension to PSS10 (Thank you Juha!), and just ordered a new 21mm sway bar for the rear to replace the factory 17mm.

I'm looking at the front, and wondering if I should replace the 20mm front bar with a 21mm. Will there be a noticeable difference for street driving? Is a 1mm thicker bar much different?

I'd love to hear your thoughts.

Thanks everyone,

Skylar

Martin S.

I put the M030 (RoW) 22m sway on the front of my 993 NB coupe, back in the day. I also put a 993 Turbo 21mm rear bar on to complete my upgrade to M030 RoW suspension (shocks and struts). All of this was done at ANDIAL in Santa Ana, CA. It worked great on the street and at the rack. So I can tell you from my personal experience that a 22mm front and 21 mm rear works. The standard M030 (RoW) sway bar thicknesses is 22mm front 20mm rear. The 993 RS is 23mm front and 20mm rear. Pete at ANDIAL suggested I try the 21mm rear turbo bar as it provided enough "meat" on the bar to drill a second hole making the rear adjustable, on the cheap.

From my personal experience, I think a 21mm front bar is too small, with a 21mm rear bar. 22mm, or 23mm would be ideal.

If I were you, I'd buy a 23mm 993 RS sway bar, and if you want to stay consistent with 993 RS specs, order the rear 20mm bar. This has worked for so many people...I have very seen a complaint about how these sway bar sizes work. The Porsche Factory designed them after all.

You may want to Google sway bar rigidity math. A 1 mm difference is huge. Check out the URL below and you'll get a good idea of the impact of changing the size of a sway bar.


Sway Bar Rate Calculator | GTSparkplugs
www.gtsparkplugs.com/Sway-Bar-Calculator.html
Enter any The Dimension A-E in INCHES and the tool will calculate the sway bar's torsional stiffness for the bar. Press CALCULATE to find other values.

phoneyman

I asked a very similar question a while back and the general consensus was: there are better things to spend money on, mostly track time or a really good alignment/corner balance, etc. I have a 21mm ARB in the rear and the stock up front. If youre a serious track-oriented driver and really dial in your suspension, then its worth getting a different front ARB, preferably one that is adjustable. If its a street driven car, spend time adjusting your coilover settings and heights before investing in a new front ARB.

nile13

For street driving it doesn't much matter. Leave things alone. Once you _know_ what the car's not doing right, start thinking of "improvements".

Start with better tires.

Martin S.

Do it once and do it right. This way you don't revisit the project, it's done. The 993 RS sway bars are right, Factory engineered and produced, and they are on the 993 RS after all. And best of all, they fit. Once installed, corner balance at the appropriate ride height and you are set. The front bars are 5 way adjustable, the rears 3 way adjustable.

Below are the part #'s you'll need, Sunset Imports sells all of this. Can't vouch for the prices...Just call Sunset and tell them you want the 993 RS sway bar parts. The list below came from them, back in the day.

1
993.343.707.81
RS 23 mm Front Stab Bar
$350.00
1
993.343.069.80
RS Drop links Front
99.71
1
993.343.070.80
RS Drop links Front
99.71
2
964.343.792.06
RS 23 mm Front Stab. Bush
4.60
1
993.333.707.81
RS 20 mm Rear Stab Bar
332.50
2
993.333.073.80
RS Drop links Rear*
142.12
2
477.411.313.C
RS 20 mm stab bush rear street
17.90
$1,046.54

clib

I agree with doing it right from the beginning.
But Are you planning to track the car?
If just street maybe wait and see how you like the PSS change first. I have the RS adjustable bars and am very happy with them and they have helped on the track a lot. But they do function as additional springs and will roughen the ride a bit. Comparing my buddies otherwise identical set up (pss9) and ROW sways there is a noticeable difference in ride comfort.
And replacing the front bar has to rank very high on the PIA scale, for me at least.

Martin S.

23mm front, 20mm rear bars will stiffen up the ride. Not the best for cushy street comfort.

I forgot how comfortable a street 993 can be...got a ride in a pal's Carrera S last year, mighty sweet.

I went over the top on mine (What was I thinking?):
-993 RS bars
-Tarrett Adjustable drop links
-MCS double adjustable suspension
-All ERP links in the rear
-993 RS Club Sport flywheel and clutch

I admit it, the car rides rough on the street...but on a track date, it's heaven. If I ever convert the car back to pure street (Not gonna happen) ...I'd put on the new struts/shocks Porsche is selling...and stock sway bars.

Edward

Hi Skylar,

First off, yes, 1mm difference in diameter makes a significant, felt difference in sway bars, IMHO.

With the fine PSS10s, you don't really want to short-change yourself with a less-than-optimal sway bar setup. You already ordered a 21mm rear (superb choice, btw, as I also have the Porsche RoW 21mm bar), and the 21mm front is not a great match given what you have, and may arguably induce more oversteer than you may like. Put a 22mm M030 front bar (heck, you can prob find one cheap used!), and the 21mm rear will be the perfect compliment. And don't forget to get bushings.

FWIW, I have PSS9s and the 22mm/21mm bars for quite some time now and the car has crisp turn in and handles wonderfully neutral (can induce over or understeer easily with driver input). I think you'll enjoy it once it's all setup.

Edward

Rick

I can check to verify if anyone is interested...the C2S I just picked up apparently has RS sway bars (I'll measure)...i would be open to a trade/cash. The car has PSS9s and will only be driven on the street so RS sways are a bit much.

NYC993

No.

Sway bars are used as tuning tools to dial-in desired under/oversteer for a particular driving style or particular track and conditions. Simply making a sway bar stiffer on one end doesn't address anything.

Juha G

Skylar, get the 993 RS bars and be done with it! I don't see any benefit of going with odd sized aftermarket bars.

Will there be a difference on the street? Hell yeah! They will definitelt make a difference to how the car feels and handles, plus you'll be able adjust the RS bars to find a setup that you like. You can dial out the inheritent understeer the C4S has with setting the front bar softer and rear bar stiffer.

Edward

So by the first part of your statement, you concede that sway bar dial in over/understeer, correct? But in the latter half, you claim that a stiffer bar on one end doesn't address anything?
Perhaps you mean to say that the OP "stiffening" only one end of the car's roll dynamics it will not "improve" his handling overall?

WRT RS bars, heck, we can all throw money at our cars, so sure, go for it if that makes you feel like you've arrived. It depends on what your stated mission is so one should always clarify one's goals, then execute a plan to meet that objective. But I will respectfully disagree that just "going for it" with RS bars is somehow the go-to answer. Moreover, the M030 bars are not aftermarket question marks but OEM units that demonstrably work great, are a guaranteed no-brainer fitment, and (if at all a concern as it is for some) far cheaper than many aftermarket alternatives, and certainly less costly than the RS ones. Not being contentious, mind you, but merely offering another angle for consideration outside of "RS" or a perceived notion of "getting the best."

Edward

NYC993

Correct. Although he did replace the rear sway bar. But without knowing how the car behaves overall and if the 1mm will actually make a difference in the right direction, it won't change much if anything. I agree that if you want to play with sway bars, just get RS ones. But again, I'm not sure who drives on public roads to the point of experiencing difference in roll bar settings.

NYC993

If by street you mean the ring, then sure.
If we are talking about dialing out "inherent understeer" why not leave the stock softer front bar in place?

Martin S.

Here is the real world. The 993 RS 5 position front bars are not as easy to adjust as the 3 position rears. I generally leave the front bar in the middle setting, same with the rear. However if I am on a twisty track and I want to throw the rear end around a bit, I move the setting to full stiff in the rear, leave the front alone.

If I am on a very fast track such as California Speedway, or Willow Springs, I move the rear bar to the full soft position...

And sometime just for s#@ts and giggles, I'll run one of the faster tracks with the rear bar in the center..get a little tail action.

General rule, if the bar is too stiff on the front, you'll be picking up the inside wheel...always better to have four wheels on the ground. I had TRG front bars before I went to 993 RS...they were about 25mm, maybe even 26mm...can't recall. They were adjustable, but I could never get them right, always picking up a wheel, breaking drop links....since I went to the 993 RS bars and Tarrett adjustable drop links a few years back....problems over.

General the adjustment of the bars is reciprocal, that is, if you are up to messing with the front bar. Tighten the front bars loosen the rear bars, loosen the front bar, tighten the rear.

In conclusion, if you are adjusting your suspension with a butt dyno, your intuition may be way off. You need a data logger with wheel sensors if you really want to know what's going on, but that's a topic for another day.