I impulse bought some 24/26mm H&R sways to go with my PSS10s only to realize they might be big for street with the occasional autocross. So today I impulse bought (Ebay BIN ) a used 20mm rear sway bar. Would this work well with my old stock 20mm front bar or should I look for a 22mm bar? Any thoughts? I can get my hands on a 21mm front bar too.

 

No recommendations on the front 20/21/22mm bars?

 

here is what was used on various 993 versions
993 Swaybars
US:
- Carrera: 20/17
- Carrera M030: 22/20
- Carrera S/4S: 20/17
- Carrera S/4S M030: 22/18
- Turbo: 22/19

ROW:
- Carrera: 21/18
- Carrera M030: 22/20
- Carrera S/4S: 20/18
- Carrera S/4S M030: 22/20
- Turbo: 22/21
- RS: 23/20 (adjustable)

the bigger rear bar relative to the usal sizes just makes for less understeer.

You might look for 22 fronts from an M030 car, they do regularly pop up for sale

 

Thanks Bill. I was just wondering whether I was wasting my time going from a 20mm to a 21mm front bar or possibly inviting handling issues with 20mm rear/20 or 21mm front bar.

 

Since you're not getting much feedback, I'll add my guesses.

The general trend in the factory spec is a proportionally larger front sway vs rear.

(Thanks to Bill)
ROW:
- Carrera: 21/18
- Carrera M030: 22/20
- Carrera S/4S: 20/18
- Carrera S/4S M030: 22/20
- Turbo: 22/21
- RS: 23/20 (adjustable)

So, if you use the same size front to rear, how is that going to affect the handling? And is this something you're after?

To me, looking at the specs I see that RS is 23/20, a bigger proportion of front vs rear over M030. I would imagine the effect is to make the car more neutral, to minimize understeer and move the balance toward oversteer. I could be wrong though.

You're proposing 20/20. To me that seems like you'd be going in the direction of the handling balance of a proverbial Honda Accord,,, lot's and lot's of push...

I have the M030 22/20 sways, if you were closer (or visiting nearby sometime) you'd be welcome to drive my car to get a sense of the handling.

Have you tried the H&R sways yet? I'd be curious to try those, myself.

EDIT: Here's a good thread, on this page there's a post by jimbo3 saying he did exactly what you're proposing and found too much understeer to his liking (for aggressive driving, anyway.)
https://rennlist.com/forums/993-foru...ignment-3.html

 

Thanks Mongrelcat. I was thinking the opposite - the car would be softer up front relative to the back causing less under steer or perhaps even over steer. Perhaps I've got things backwards. I think I'll just look for a 22mm front bar new or used rather than experiment with the 21mm bar. As for the H&Rs, they are installed. The ride quality is pretty good on the street set on 4r/3f (soft side) and was even ok on 5/5. It was a little rough over our heavily patched roads but nothing alarming but it makes a better highway car than city car. I did a high speed autocross with the 4/3 settings and I think it pushed some but the reality is I'm along way from knowing what to tinker with when it comes to suspension. I'm only guessing that if I go full stiff on the back to correct it that the ride quality will not be good. This is where a set of M030 bars comes in. I'm curious to see what the difference is but I'll crank the PSS10s up for the next autocross while I collect parts.

 

keep in mind spring rate of a bar is diameter to the 4th power -- so a mm up is a considerable rate increase.

 

I WENT from stock to sport bars after I put in the M030 springs and Bilsteins. This was just right and noticeblay increased tossability. 20/17 vs 22/20 is a BIG difference since the roll resistance is proportional to the square of the diameter - 20/17 squared is 1.39 vs 22/20 sq= 1.21. Almost 20% less undesteering effect from the sports bars, and not a huge ride diffeerence (at least on my car where the Bilsteins and sports springs are - well - taut, anyway). I don't get the spring rae analog, but as a torsion bar it is square I believe.
Charlie

 

I would try and keep 'balanced' sets upfront and rear - either in OEM that are used in various versions of our cars or aftermarket, but keep the differences in diameters recommended by Porsche (if using oem or H & R if using H & R, TRG etc). There is usually a reason for the differences in sizes front and rear. Although it is fun to play around with different sets/settings, (ie trying 20/20 which would give you oversteer), and fun to have some oversteer, it is only fun when you're driving slow enough that it doesn't make a difference. You only need to loose control from too much oversteer in a high speed turn driving at your limit to understand why other people have selected these sets for your vehicle...IMHO

 

The noted understeer was (is) due to camber differences (aggressive in the rear, very mild in the front), not from having 20mm bars at both ends. I was pointing out that even the larger bar in the rear didn't completely overcome the understeer from the camber issue, but it helped. Since then, I've dropped the front tire pressure to 34 (from 36) and that seems to help a (very) little bit. One of these days, I need to get to the shop for some addt'l front camber....

 

And that's a lesson to me to not be guessing in threads that I have no clue about, sorry.

 

The 20/20 will have less understeer/more oversteer than 22/20

I don't know if the origianl poster wants that or not. When I bought mine it had th RoW M030 suspension including 22/20 bars. I t was preety good for a stock suspension.