Sway bars & torsion bars

[larkja]

I've been looking through my Hayes manual and this forrum but not able to get what I'm looking for. (I have an '82 SC)

I plan on upgrading my suspension and asked a question earlier - great responses, thank you.

I understand that the 911s use torsion bars instead of springs. Unfortunately, I'm not exactly sure how they work, where they connect, how they adjust, etc. Also, are they front and rear?

Same goes for the sway bars. Pelican seems to use torsion and sway interchangeably so I'm a little confused.

Are there any diagrams you have come across that will show me how these suspension components work? Also, when I upgrade, how the new pieces are installed and how/why they work better? i.e. larger sway/torsion bars.

Thanks,
Jim

[Rot 911]

Here is a diagram of your front suspension. Part number 21 is the torsion bar (one on each side) and part number 22 is the sway bar.


Here is your rear axle, part number 34 is your torsion bar, again one on each side:

[djmcmath]

Torsion bars -- like springs, except they use the rotational force instead of a linear force. I guess on a materials level, it's the same internal forces, but they're arranged differently in the car. Anyway, the t-bars have splines at both ends. Setting the splines places a preload on the "spring," which allows the car to settle at whatever height you want it (within reason).
The fronts are really easy to get at: pull the 11mm adjusting bolt (#19), remove the adjusting end cap (#18), and pull them out.
The rears are a bit more challenging, as there's some fairly serious disassembly that needs to go on to get them out. The bar (#34) sits inside the tube (#1), and comes out through the end cap (#35) and spring plate (#26). To get the bar all the way out, you have to remove the little round t-bar hole, which is easy, and the rocker panel, which is hard (not shown in the above pics). The get the spring plate off, you have to pull either the height adjusting bolts (#31, 32) or the toe/camber adjusting bolts (#27 and ... hmmm, can't find 'em). You'll need to align the car after replacing/upgrading torsions anyway, so pulling all of the bolts out, replacing the bushings, and cleaning/painting the spring plate is a good idea.

Sway bars aka Anti-Roll Bars -- connect one unsprung side to the other unsprung side. Normally, the sways are unloaded. They transfer a difference in load from one side to the other. When you go into a corner, weight transfers to the outside wheel, compressing that side of the suspension. The sway takes that change in chassis-control arm position and loads up the other side, in effect "transferring" some of that load to the inside unladen wheel. Thus, sway bars reduce body roll when cornering. It should be noted that if the sways are too big (in relation to the springs/torsions), the car will tend to "dive" in corners. The big bonus in sway bars is less the size and more the adjustability. If you can preload a bar to a certain point, you can adjust the oversteer/understeer characteristics of the car to your liking.

Does that help at all? I'm sure the experts will come past in a few minutes to correct my technical errors, but I'm hoping to have answered at least a few questions.

Dan

[larkja]

Thank you. Very helpful. Last question. For a simple suspension mod (sounds like the rear torsion may be a bit of a challenge), would front and rear sway bars be the best first step? Looks like those may be easy to change out. I have the stock '82 SC components. Any thoughts on sway bar diameters so the car doesn't get too messed up?

My next project will probably bet the torsions - once I am a little more familiar with the car and have a few more PCA DEs under my belt.

Thanks again,
Jim

[jluetjen]

Larkja, before you start changing sway bars and T-bars, what is it that you are trying to accomplish? You said "upgrading" -- in what fashion? It's not like stiffer is better and rock solid is best. Suspension tuning is about balance and hitting the "sweet spot". The "sweet spot" will change depending on the tires, venue and driver -- so changing things without a plan is a good way to mess things up.

[anthony]

I'm planning on putting Carrera sway bars on my SC. The Carrera bars are slightly thicker and should be a nice upgrade. I figure it will be fairly easy to swap them over and on the plus side, the Carrera bars were cheap. I already had the front and found the rear on ebay for $35.

If you upgrade to through-body sway bars the installation can be quite involved. And through-body sway bars aren't inexpensive.

[larkja]

I am planning on getting more involved with PCA time trials. I drive the car on the weekends and will be driving to and from the track. I will not be purchasing two sets of tires/rims - I know, I'll be compromising.

Rather than doing engine mods, which means I'll just get into more trouble sooner, I wanted to start with the suspension. I have driven the car on the track with the SCCA (HPDEs) and was pleased with the performance, but it seemed a bit cushy.

I would like a solid, stable platform that will grow as I get better. So I'm thinking adjustability might be a way to go - maybe more expensive, but better in the long run.

Thanks,
Jim

[randywebb]

get Sanders hollow torsion bars if the cost is not a problem

SRP makes the best sway bars, followed probably by Tarrett.

read some posts - you search on polybronze, poly-bronze

it is cheaper to read than to buy....

[larkja]

I appreciate the info. So, based on my application, would you recommend sway or torsion, or save and wait a while longer and get them both at the same time to avoid the "nose dive" issue.

Thanks,
Jim

[djmcmath]

Stock sways on an '82 aren't too bad, iirc. Seems like some SC people upgrade to the Carrera torsions, which is affordable because the Carrera people are spending money on new Sway-A-Ways.

I probably overstressed the "dive" issue -- I've only read about it, and can only discuss it from a theoretical standpoint. I've never heard of actual racers complaining about sways that were too big -- but then, I can't think that I've sways bigger than about 22mm popular in our application, either. (shrug) Try a search -- seems there's a lot more data on this topic than I feel comfortable trying to expound on.

Dan

[jluetjen]

I would like a solid, stable platform that will grow as I get better. So I'm thinking adjustability might be a way to go

I think that this is a good overall strategy. Surprisingly, any 911 fits your first objective -- "a stable platform that will grow as I get better".

When you lap or do an autocross course -- how consistant are your times? If you are doing autocross -- how consistant are your last couple of runs? Unless you are lapping consistantly within the same 1/2 second (excluding traffic) or have similar consistancy on your last autocross runs, a stiffer car may hurt your driving more then help it. The benefit of a "cushy" car to a novice driver is that it gives BIG AND CLEAR SIGNALS TO THE DRIVER WHAT IT IS DOING . This allows the driver to feel what the car is doing; Which corner is losing traction? Has the car settled yet? How close am I to the limit? As the suspension gets stiffer, the signals come faster and get more subtle. Experienced drivers can feel them and react, novice drivers are oblivious to the sensations. The result will be that a novice will overdrive a stiff car.

My suggestion would be to start with a good set of adjustable sport shocks. Adjusting the shocks will have a far more noticeable affect to the driver during the critical transition stages of cornering without affecting the fundimental ballance designed into the car's set-up by the factory. Adjust the shocks and tire pressures as needed to dial in the balance of your car. As you are driving try to be very sensitive to the messages that the car is sending with it's suspension motions.

For example as you are driving a certain corner (or corners) you may notice the car rolling over onto the outside rear tire and causing oversteer. By modifying your style of throttle application and line try to manage that process so that you keep your speed up without overtaxing the outside rear. Maybe you roll a little more speed into the corner entry to keep the weight towards the front, or maybe you trailbrake a little, maybe it's less brake and throttle and just a higher average speed. Moving to a stiffer suspension will reduce the signals and make it harder for you to learn these techniques. Driving in rain makes the car's signals one or two magnitudes smaller -- which is why racers usually disconnect one or both sway bars when racing in the rain.