Will upgrading sway bars make justifiable difference?

[Trackrash]

Another thing to consider are bushings in your suspension. I found that with larger wheel and tires, not to mention torsions and sway bars, that the stock rubber suspension bushings are inadequate. They give a lot and allow uncontrolled movement of suspension pieces.

[richde]

I saw this on my current car's BBS, still shopping and researching for a 911....

TO REDUCE UNDERSTEER or INCREASE OVERSTEER:

Front tires:
- Increase tire pressure in 2.5psi increments
- Increase Section Width
- Lower the Aspect Ratio
- Reduce front tread depth

Rear Tires:
- Reduce tire pressure in 2.5psi increments
- Reduce section width
- Install higher aspect ratio tires
- Increase rear tread depth

Front Wheels:
- Install wider wheels
- Install lighter wheels

Rear Wheels:
- Install narrower wheels
- Install heavier wheels

Front Alignment settings:
- Dial in more negative camber
- Dial in More toe-out
- Dial in more positive caster

Rear Alignment settings:
- Dial in more positive camber
- Dial in more toe-out (Same as front)

Anti-Sway bars:
- Soften the Front
- Stiffen the Rear

Spring rates:
- Soften the Front
- Stiffen the Rear

Shock absorbers:
- Soften the Front
- Stiffen the Rear

Suspension Bushings:
- Soften the Front
- Stiffen the Rear

Brake Proportioning
- Reduce Front brake pressure
- Increase rear pressure

Weight Distribution
- Reduce front weight
- Increase rear weight

Aerodynamics:
- Increase Front Downforce
- Reduce rear downforce

---------------------------------------------------------------------------------

TO REDUCE OVERSTEER or INCREASE UNDERSTEER:

Front tires:
- Decrease tire pressure in 2.5psi increments
- Decrease Section Width
- Install higher Aspect Ratio tires
- Increase front tread depth

Rear Tires:
- Increase tire pressure in 2.5psi increments
- Increase section width
- Reduce aspect ratio
- Decrease rear tread depth

Front Wheels:
- Install narrower wheels
- Install heavier wheels

Rear Wheels:
- Install wider wheels
- Install lighter wheels

Front Alignment settings:
- Dial in less negative camber
- Dial in less toe-out (to toe-in if needed)
- Dial in less positive caster

Rear Alignment settings:
- Dial in less positive camber
- Dial in less toe-out (Same as front)

Anti-Sway bars:
- Stiffen the Front
- Soften the Rear

Spring rates:
- Stiffen the Front
- Soften the Rear

Shock absorbers:
- Stiffen the Front
- Soften the Rear

Suspension Bushings:
- Stiffen the Front
- Soften the Rear

Brake Proportioning
- Increase Front brake pressure
- Reduce rear brake pressure

Weight Distribution
- Increase front weight
- Decrease rear weight

Aerodynamics:
- Reduce Front Downforce
- Increase rear downforce

I always thought this was a universal guide, and a few things struck me as strange while reading here. The wildly upgraded spring rates of bigger Torsion bars (how the struts handle that, I don't know) and the use of T-bars to control body roll rather than upgrading sways. Especially seeing how easy it is to change a sway bar.

[stlrj]

Why anyone would like to increase understeer is beyond me.

[911pcars]

Originally Posted by stlrj

Why anyone would like to increase understeer is beyond me.

I suspect the proverbial racing stripe in the seat area is more easily created when negotiating curves at high rates of speed with an oversteering vehicle. I'd be a little nervous. Maybe more than a little.

A worthy goal is Neutral at all speeds with 2nd place being slight oversteer on slow corners and slight understeer at high speed. However, Porsches have their own peculiar road handling characteristics. Throttle-induced understeer is usually the answer to avoid backing into a tree at high speed.

Sherwood

[goldsc78258]

subscribed

[ToddM]

The suspension is a ***system*** and needs to be treated as such. Upgrading one component alone without taking this into consideration is a bad move. If upgrading step by step, it should be per an upgrade plan and parts should be chosen towards forward migration.

Reg. targa and cabs, you are always going to be limited by the lesser structural integrity of the chassis. I'd be reinforcing the chassis before I did major suspension modifications or heavily flogged the car. I am sure the extra weight of the 3.6 is not helping in this particular situation.

Best solution here is to get a coupe for DE, IMHO (and no, I am not trying to be smart ass with this comment)

[Steve@Rennsport]

Originally Posted by ToddM

The suspension is a ***system*** and needs to be treated as such. Upgrading one component alone without taking this into consideration is a bad move. If upgrading step by step, it should be per an upgrade plan and parts should be chosen towards forward migration.

Hmmmmmmmmm,....Sounds familiar,...

[sbrown.nw]

I would not go stiffer than 21/27 torsion bars in a Targa. I had 22/28 in my first 911 (78 SC) and they were too stiff for the chasis. I have 21/27 with the sport shocks and 22mm sways in the front and rear on my 72 Targa. The car seems very neutral with a little bit of butt sway so I might tighten up the rear bar one or two positions.

Opinions? TIA,

Scott

[Trackrash]

The one thing I learned, having BTDT, is it is all about what tire wheel combo you plan to run. Decide on your tires, then look at what others have done to their suspensions that work with those same tires on similar cars. Tire grip, wheel and tire width, etc. will dictate what you need to do to your suspension.
After I went to 7/8 x 16s on my 911 from 6/7 inch wheels the rear was way to soft. I upgraded to 26mm rear torsions and 21mm rear sways. It was perfect with street tires, even when autocrossing.
Later I put on a set of RA-1s and suddenly my suspension felt way to soft. I now have 22/28 torsions.
What can you learn from this?
It's a slippery slope.

Gordon

[Flieger]

Trackrash, what kind of 911 do you have? I have a 1971 911S with stock torsion bars 19mm front and 23 mm rear. I have Weltmeister adjustable anti-sway bars. The car weighs 2000 pounds without a driver due to the fiberglass panels. It has a 2.7 liter MFI RS spec engine and 16x7 front, 16x8 rear Fuchs

I think it is OK, though the worn-out hard rubber bushings may make it seem stiffer, along with the squeaking of the TBs.

Do you think I need to adjust the torsion bar balance to make up for the shift in weight distrubution to the rear, even though the total weight is lower? I have heard 21/24 bars are good.

How do your car specs compare?

[Trackrash]

Sounds like your car is similar to mine. I'm running Toyo RA-1s 205/225 16s with RS flairs. Engine is a short stroke 2.5 with webers. Weight is about 2000 lbs with out the spare, jack etc.
I doubt you will be able to tell the difference between 23 and 24mm rear torsions.
Again, a lot of it depends on how you are going to use the car. If you aren't tracking the car I would recomend stock 19s in front and 25s in the rear. 25s are stock size on the newer Carreras.
For track use you need something a lot stiffer.
The problem with using stiff sway bars with not so big torsions is front/rear pitching. The front and rear will dive and squat all over the place even if the car doesn't lean much to the side.
You really should consider upgrading the suspension bushings. My car's torsion arms were bottoming out metal to metal. New or hard bushings also limit the toe change in the rear under cornering or braking/acceleration, which really helps the handling and feel of the car.
Another factor is how much if any you have lowered the car. The lower you go the stiffer it needs to be.
You should also check the bump stops in the shocks. In a lowered car your front suspension is resting on the stops, making for a harsh ride.
My car rides better and handles WAY better after going to 22/28 torsions, poly graphite bushings, 24" ride height, and cut down bump stops. The only down side is it is harsh over small sharp bumps like the dots on the freeway. It is actualy smoother through dips and potholes.
Do some searches there are really good threads about torsion bar size like this one. 22/28 vs. 22/30
Here are pictures of my car, the white one a little down the page. Show me your narrow bodied early hot rod!

Gordon

[dfink]

Slow down in the corners and easy off in the straights and the car won't lean as much. Cut the top off and make it a cab. You are already too fast.

[Flieger]

Hello Gordon,

Cool Car.

Thanks for your suggestions. I am planning to upgrade to PolyBronze bushings but am $aving until the old ones basically fall out. College and other stuff is a real drag to pay for.

I have the car at pretty much a stock ride height. I had to lower the front a little after taking the weight off in order to get the rake angle right. I think I will go with the stiffer bars when the time comes because the car is for very agressive street driving on weekends and for autocrosses.

I agree about the sway bars. The proper way to control roll is through stiffer torsion bars (primary springs) Or to raise the roll center and lower the center of gravity but that can be expensive and complicated.

In the future, I am thinking PolyBronze bushings and 22/25mm torsion bars.

RSR trailing arms would be nice but I am dreaming now.

Maybe I will just stiffen the rear sway relative to the front to make turn in quicker

[Chris'85]

I saw one comment in here regarding coil overs. I have an '85 Targa and was toying with the idea of installling coil overs and removing the torsion bars. This is basically a street car that runs a few auto-Xs. Any thoughts on this?

[efhughes3]

Originally Posted by Flieger

In the future, I am thinking PolyBronze bushings and 22/25mm torsion bars.

Isn't that a bad combo? I'd think having such stiff front t-bars with only 25's at the rear would cause huge understeer.

[rfloz]

Originally Posted by Chris'85

I saw one comment in here regarding coil overs. I have an '85 Targa and was toying with the idea of installling coil overs and removing the torsion bars. This is basically a street car that runs a few auto-Xs. Any thoughts on this?

I assume you want coil-overs to get more stiffness than T-bars can give (you didn't say what you have now).

I have 22/29 T-bars (w/ 22/21 sways, re-valved Bilsteins) and can't imagine wanting the car any stiffer on the street. I do 10-15 autox's and hope to do 4-5 DEs's per year and so far I am happy with this set up. For a serious track/race car, with a cage, coil-overs probably make sense. For a street-driven car, it seems like over kill.

Bear in mind that coil-overs can limit front tire/wheels size. Serach for Jack Olsen's decision to return to T-bars in front after trying coil-overs for mjust this reason.

Also, see above about diminishing returns on making targas stiffer.

Edit to add - I recommend you go for a ride/drive in a more stiffly sprung car before you make your decision. If you are in the L.A. area or attend Orange Coast Region auto-x's, I'd be happy to give you a test ride.

[Eagledriver]

It looks to me like you would get the most benefit from lowering the car. You already have stiff enough suspension components. I'd also say that for DE who cares? It's more fun to drive a slow car fast than a fast car slow.

-Andy