Ideal torsion bar setup for street and light track use?
 

I know this has been discussed many times before but I am looking for more specific advise.

I doing mostly aggressive street driving and would like to take the car to the track in the future and it be able to out perform my driving abilities. :D

The car is pretty much full weight around #2700 with only minor suspension mods such as late Carrera sway bars and a strut tower brace. It is a '77 911S.

What torsion bar front and rear would be ideal to give me the extra performance I am looking for without beating me to death when you run over a small dip or imperfections in the road.

I am also running 18" wheels.

Thanks for any advise.

Personally, I would go with smaller wheels (like 16") and leave the stock torsions in place. After you verify that your bushings are ok, and replace those that need replacing (most likely the rear spring plate ones and, possibily the fronts as well). Then take your car to a shop that specializes in setting up 911 race cars, tell them what your intent is, have them lower/align/corner balance as needed.

My '73 is running stock torsions with 19 mm front and rear ARBs. I am running 15" wheels with 55 series Yoko ES-100's. Jeff Gamroth (Rothsport) did a great job getting me setup to get the most at AX and still have a (more or less) comfy street ride.

What extra performance do you desire? And why 18s? What size tires are you running? Is the rear flared?

I am running solid 22/30mm bars and the ride is just as good as original but I attribute that to the Elephant Racing suspension bushings I had installed. My car is heavier than yours so you might want to go a little smaller but I think your 18 inch rims will cause a rougher ride than bigger bars because of less sidewall flex.

22/28 up to 22/30. I'd avoid the 23 in front for all but the serious track car. The front bar at 22 are a little jarring. I had 28 in the rear and then chaged to 30's. I saw little degredation in ride quality with the change in the rears. I suggest getting new shocks at the same time. You can try to match with Bilstein sports or HD's, but I recommed getting them revalved to match your car's weight, torsion bar size, and driving requirements. Calling Bistein direct or SmartRacing will help in getting the setting you want. Most likely your ride is rough already from 18 wheels.

I have 21/26 and I do pretty much the exact type of driving you're talking about. The ride is perfect for the street and has done well in multiple autocross and one track event. I didn't want the "jarring" of the 22 up-front as 89911 describes. Honestly, selecting the rear size was the hardest part as the 21 in front was a no-brainer for me.

Thanks for all the advise everyone. Any other opinions are always appreciated.

Given your intended use, I'd go 21/27. Your 18s will degrade ride quality and stiffer bars in combination with that are going to be harsh on the street.

The 21/27 will give a big increase in control over your stock setup and will be a big improvement for the occasional track day.

If you get the opportunity, it's a good idea to take a drive in a car similarly setup before you make the changes. But note that the car must have other similar items for it to be a valide test (18 inch wheels, same shocks and bushings).

Chuck is right on. Too often we opt for way too stiff suspension when appropriate street use is desired.

Everything here is a compromise. There are engineering trade-offs for every situation and set-up. The poster is asking a very difficult “what fits all” question. Some of these can’t be answered without experimentation. Chuck’s admonition to drive similarly set-up 911s is right on. Even then, you should be prepared to adjust again.

None of this should be cast in stone. Your driving style and track needs will change over time. You will want to have your suspension set-up follow that progression.

Best,
Grady

I agree with 21/27. If your circumstances call for more track use or extremely smooth roads, 28's in the rear might be in order. Opt for heavier torsion bars over the typical heavy duty sway bar options; there's less impact on road harshness.

Sherwood

I have 21/27 on my SC and really like the set up. Bilstein HD in front and Sport in the back.

If you keep your 18" wheels, you will not have a lot of rubber helping softening the ride. anything over 22/29 will rattle your fillings out.

Also remember that you can add stiffer sway bars from some more stability without compromising the street ride at all.

George

Sounds like 21/27 is the best starting point for me. What is the stock torsion diameter on my car? '77 911S
Thanks again.

Not sure, what your bars are, but the 86 carrera is a direct bolt in upgrade. Not sure if the G50 equipped Carrera is, but the 86 is for sure. 85 and earlier are smaller. A set of Carrera bars generally can be found for around $150 or less from Carrera owners who upgrade their track cars. If you want more than that, you will need through body bars, which means cutting into the tub. Not necessary in my opinion, especially for what you want to do.

Cheers, George

Added to avoid confusion:

George,
Torsion bar is for chassis suspension (like a coil spring).

Antiroll (sway) bar is also a torsion bar but to control weight transfer when cornering.

Not the same.

Sherwood

Geez. It's not that I don't know that. I misunderstood the question and yes, my post above talks about sway bars.

Stock torsion bar diameters for 77 should be 19/24 or something even less.

George

George,
I was confused by your sudden seque to sway bars when we there was a question about stock torsion bar sizes. Sorry.

Sherwood

Sherwood.

The "Geez" above was directed to myself, sorry if I did not make that clear! No need to be sorry, as I was completely misunderstanding the question!

Cheers,

George

I guess nobody knows what the stock torsion bar diameter is?
I was thinking something like 19/24? Or am I way off?

19/23

I've got 22/28 and the front is just a little bit much for the street IMO. As suggested 21/27 or even 21/28 would be good.

I'm a big fan in starting with torsion bars and shocks, when you want to improve your suspension, and then moving on from there.

I see you already have Carrera anti-sways. I think you'll find that they are more than adequate, for your use, when combined with the bigger torsion bars.