Torsion bar question

I'm currently thinking 28/21.

For those of you who have gone to stiffer bars:

Would 30mm in the back knock my fillings loose?

Weltmeister or Sway-A-Way?

Are the weight savings from hollow bars meaningful?

Thanks.

------------------
Jack Olsen
1973 911 T (3.6) sunroof coupe
jackolsen@mediaone.net

[This message has been edited by JackOlsen (edited 02-05-2001).]

Jack,

As a dentist and purveyor of a professional opinion on this one, I would have to say it is highly unlikely that you will loose any metallic, ceramic, or resin based dental restoration as a result of your use of 30mm torsion bars. I'll let my collegue, 89911, chime in on this one too.

As for the resulting change in your suspension, I'll leave that to those who have more experience with such a modification.

Hope I at least made you chuckle.

Nicholas D. Shumaker, DDS


------------------
__________
Nick Shumaker
1982 911SC Coupe

Nick, Hey, how you doing. I will be out in Steamboat Spring Feb 14 to 18 at a conference by the way. The torsion bar issue is one that I think will change your car to a dedicated track car or a street drivable car. The decision you have to make is the sacrificed ride quality worth the amount of track driving done. I drive my car about 6 weekends a year at tracks and not much else. It wasn't as much an issue for me. If I was driving semi-weekly, the pounding would start to get to me. I also may sell the car sometime. You never know. The buyer may not exactly like the firm ride. So my decision was a compromise and I went with what B. Anderson and other had recommended. 22mm and 28mm. My car handled well with the 18.8 and 25 stock. Just some body roll.

About those fillings. Did you ever notice that ever patient that loses a filling has to tell you what they were eating. Like certain foods will void their warranty. Always a bagel or something. Hey, I get on this board to get away from work, back to Porsche talk!

------------------
8 9 9 1 1, The last of the line.

Jack,

I have 22/28 MM bars on my 911's; I used Sway-A-Way bars. IMHO, this combo is very drivable on the street and very enjoyable at Driver's Ed events.

I have a friend with 30 MM rears on a '88 Carrera. They are not to bad on the street, except for rough surfaces or "washboard" pavement when things get a little jumpy. Unless you are a heavy track "junkie", I would suggest stay with the 21/28 MM bars on your '73 911.

Regards, Bruce

To keep this on a Porsche note...

Do any of you know the sizes of the factory torsion bars that came on the SC's? Mine's an 82. I'm putting in the Weltmeister polygraphite bushings soon and I'm thinking about doing torsion bars too. Just wondering where I am at now.

Thanks in advance!

Nick.

------------------
__________
Nick Shumaker
1982 911SC Coupe

Jack, Actually I'm surprised you haven't done this already. I installed 22 front, 28 rear on my 78SC. I have noticed very little if any harshness to the ride quality for a daily driver. I did gain a significant amount of road handling. I strongly suggest the upgrade. Bruce Anderson suggests the 21/27 for the lighter pre-74 cars. Due to the increase in rear weight, with that 3.6, I would think 28's in the rear would be the way to go. After all the turbo's had larger bars to compensate for the extra engine weight.

I believe the installation of stiffer swaybars are what will knock your fillings, if anything. For a daily driver I would go with a small if any change to them.

I went with the Sway-Away solid bars and have been happy. I too posed the question of hollow v. solid a while back. Warren replied that the extra weight saved is not worth the cost and would really be insignificant on a car of the SC weight. I know yours is light, but i don't think you'll gain that much of an advantage. Your wallet will feel lighter, however.
Just my .02.
-----------------
Paul
78SC Targa

Hi Jack,

I think 21/28 is a fine idea for a dual purpose early 911 with a 3.6. I have 21/27 hollow bars in my '72S with 2.7 RS spec MFI engine and it is a good compromise for road and track with that weight of engine (probably 100 lb. lighter than your 3.6). If you want a track only car, I would recommend 23/31 hollow bars. That's what I have in my '72T with 3.2 - the cornering is flat, but it gets old over expansion strips on the highway. I personally feel torsion bars have more influence on ride quality than sway bars, partly because the later are usually adjustable.

Randy W

I'm putting 29mm rears on my '85, but I'm staying with the 18.8 fronts (stock). My car is mostly a street car, with limited AutoX and TT time. I was advised that too stiff on the front is not good for the street. The surface conditions on track are much more predictable than the street, so a heavier bar is ok for racing. But the potholes and other land mines that one encounters on the street can bend the stamped steel A-arms over time. I'll let you know how it works out. I can always go heavier on the front later.

I did the 22/28 on my 83 cab....noticeable difference in all driving. Smooth roads tracks nicely, but I also aligned, corner balanced and lowered it. Wash boards are a little harsh, but the ride improvement is worth it.

I will also be upgrading the sway bars to the 22 front and 20 rear 85 Carrera oem. This should be the last suspension work I will do. I am bumping the max on Street Stock classification.

GaryF -- Either your friend has it in for you or is uniformed. I tried the 28 on back with stock on front, and you cannot believe how fast the car rotated in a spin, or how short the to spin transition. To the point that a friend declined to drive it in an autocross. My technique had been to change something, then autocross it, before taking it to the track. It was a good learning experince. Fortunately, the fronts were easy to change before Watkins Glen. I use the car on the road frequently with 22/28 combination and probably could have gone to a 29 or 31. Remember this is an SC that weighs 2605 with 15 gallons of gas onboard and no driver and your car is probably lighter than that.

Alan
83SC

I have no direct experience with torsion bar swapping but it occured to me that for a street/track compromise, wouldn't it be better to have adjustable anti-roll bars rather than stiffer torsion bars?

My reasoning is that stiffer torsion bars would be effective at controlling dive and squat but less so at roll control, which is more the job of anti-roll bars. With adjustable anti-roll, you can stiffen it very significantly at the track and soften it again for the drive home and to work. Anyone care to comment?

Btw, what are the stock torsion bar sizes for a 1984 930? And what are the advantages of coilover springs compared to torsion bars?

Thanks for the input, everyone. It looks like 28/22 is the best overall street-track compromise. However, a few guys I've talked to with 28 bars in the back have said that they now wish they had gone with even stiffer rear bars. It's also been pointed out to me that the torsion bar equivalent of the coil-overs in the 964 that my engine came from would be 34.5 mm! Granted, my car is a lot lighter than the 964, and torsion bars and springs don't really lend themselve to apples-to-apples comparisons, but it's got me thinking.

Bruce Anderson suggests 28/22 for later cars, and 26 or 27/21 for earlier ones. He recommends Sander Engineering torsion bars, and he acknowledges:

"Some people have run much stiffer spring rates on the rear of their cars than what I recommend, and they swear by it, but I have no personal experience with this setup. They are running with the 22-mm front and 31-mm rear torsion bars."

This lines up with suggestions I've gotten from a couple of guys to go with 30/21. As to whether the new spring rates will cause extreme oversteer in my car, I'll let you know. But understeer has been the consistent tendency with Black Beauty (and its torquier engine and wider rear tires). I've got it set up fairly neutrally now, but that's with the front sway bar full soft and the rear sway bar full stiff. I suspect that even with the 30mm bars in back, I'll be able to get balanced handling with some more reasonable sway bar settings.

So, my new plan is Sander Engineering bars, 30/21.

------------------
Jack Olsen
1973 911 T (3.6) sunroof coupe
jackolsen@mediaone.net

[This message has been edited by JackOlsen (edited 02-06-2001).]

Jack,

I would seriously advise against 21/30. Nobody I know in autocross or track uses such a combination, nor is it advised by any of the mechanics/tuners in my ares (and being in Microsoft country, literally hundereds of 911s have been setup for the track here by Daytona class winning people). If your running full stiff on your front swaybars and full soft on your rears, you also have an imbalance now somewhere. Your site specifies 22mm front and rear bars - are these Weltmeister, or a through-the-body type like TRG or Charle bars? The later are what you want, and most serious track people run a bigger sway bar on the rear. What kind of shocks? Are they adjustable? A good minimum beginning choice for your car/purposes would be Double adjustable Konis (yellow) or better yet Penske, JRZ, or Moton. Red Konis won't do it in the long run, and as much as I like Bilsteins, they are not easily adjustable.

The usual order of choice/adjustment in setting up a suspension is: first - springs (torsion bars), next - sway bars (anti-roll bars) and lastly - shocks (adjustable). By choosing a 21/30 torsion bar based on your sway bars, you are starting off in the wrong direction and will be forever fighting a baseline built on oversteer. Since you have done so much that is right with your car, I'd hate to see you get this wrong. A 22/30 or 21/29 would be a better choice than 21/30. Email me if you would like further assistance.

With best regards,

Randy W

I'm certainly no expert here, but can't resist expressing myself anyway. Jack, it sound slike you have reviewed the literature fully. It seems to me that Bruce A. agrees with the post just above in that the first upgrade should be the torsion bars. It's high time for you to make this upgrade.

Further, while my car has a really fun oversteer at 20mph, it goes away quickly in autocross maneuvers where I have substantial understeer. I hate understeer. Feels like a 1965 Ford Galaxy 500.

And finally, while our roads here in Washington lave a lot to be desired (ruts, grooves, expansion joints, broken pavement and potholes, swells, etc), California roads are, I believe, much smoother. I therefore would not be scared of the 30mm rear torsion bar. If I lived in California. In Washington, those bars in my daily driver would probably cause brain damage. I mean further brain damage. Accidental brain damage. As opposed to my regular drain bamage.

------------------
'83 SC

I going with 28/22 with 22 sway front and back also new bushing from weltmiester along with solid motor and trans mounts. I also took the advise from someone on a similiar thread and sprung from adjustable springplates. I plan to have the car corner balanced when finished.

Skip 77 911 3.0

Jack,
I'd take a second look at that setup as others have advised. It seems like the car might oversteer on high speed sweepers, and this is where you cannot afford to oversteer. Your setup sounds more like an auto-X setup. Maybe you should consider going to coilover suspension at this point also.

21/30s have been ordered. If I run into problems with high speed sweepers, I'll swap 22 mm or 23 mm bars into the front for balance. As I understand it, the front ones are easier to change out. It'll be a while before this work actually gets done (with the brakes, etc, there are a lot of pieces to put together), and I want to get in an event or two first. But I appreciate the input, and will keep everybody posted.

------------------
Jack Olsen
1973 911 T (3.6) sunroof coupe
jackolsen@mediaone.net

Take about coil over on per-89 car. Is it a good upgrade without stiffen the chasis? I've heard that the strut towers were not designed for spring. Anybody done this conversion please give me some input.
Andy

Jack,
Just re did my entire front end with new everything--Turbo ties--ball joints--koni adj inserts--and 22mm welts...making the completion of 22/30 to handle that massive weight I have in the rear.
I'm meditating on what to do with sway--but they will be through body, and adj. all the way around.............S
Did you get the wiper assemb?

The only reason for going to coil overs is if you run out of suspension stiffness. There is a limit to how big in diameter you can go in torsion bar size. Coil springs can be made stiffer. With an early lightweight car, coilovers are completely unnecessary unless you have a monster engine and steam roller size tires. You'll run out of chassis stiffness and will be using the chassis flex as your suspension unless you cage it. Unless you're building a serious racecar the coilover conversion isn't practical.

------------------
Tyson Schmidt
72 911 Cabriolet