Torsion bars and sway bars...which one!!??

[rdane]

I am rebuilding/upgrading a stock '79 Coupe.

I have already replaced the shocks, ball joints and added turbo tie rods.

Looking around underneath the car the bushings are looking pretty sad.

I want to use the car for the occasional DE days, a number of track days and maybe some autox. But in general it is a 3rd car used as a fun toy when the sun shines and I can sneak in a quick 3/500 mile sprint in over a weekend.

Car is light years ahead of where it started as of now. Torsion bars and sway bars seem to be next on everyone's list.

I understand the use and need for both I *think*.

I don't want to fiddle with changeing settings. I suspect I'll not have the time or inclination to get that involved. On the track I need seat time not wrench time. The car drove well enough to thrill me when I started this project so I am easily impressed But I do want to make the best car for my own use.

With my limited understanding it would seem stiffer torsion bars and new bushings are a given just considering their age. Sway bars? New versions of the old ones or new adjustable bars?

Are the sway bars something I am going to be excited about in the end (shocks and Turbo tie rods are) and consider it money well spent @ 1600/$1800?

I have had two shops tell me that adjustable sway bars are the next step. Another tells me that you needn't bother till you get new bushings all around @ $1000. No one has suggested Torsion bars yet. Opinions?

Thanks for the input!

[jluetjen]

My recommendation is to replace the bushings and spend the rest of your money on DE's and driver improvements. The bushings should be in good shape so that the car will be predictable. If they're shot, then your wasting your time and money making other updates.

Once the car is predictable (ie. new bushings), the biggest improvements can be found in the driver. Making the car stiffer (either with the T-bars or Swaybars) will just make the car less forgiving. And forgiving is something that a novice driver wants in a car.

Once you find that you can lap at least 5 laps within the same 1/2 of a second (and I'm being generous, within the same 1/10 should be your target), then you are consistant enough of a driver to think about making changes to the car. At that point you will know that the car is always pushing here or loose there. That's when its time to start spending money on tuning the suspension.

[Green 912]

Increasing the spring rate (thicker torsion bars) will have the most dramatic and positive effect on the cars handling. Adding only fat, tight sway bars will make the car feel tight but in reality when pressed by spirited or on track driving will handle less well. The suspension you now have is an independent suspension why would anyone want to connect them with stiff sway bars? Install thicker torsion bars and replace the bushings if needed at the same time then use the sway bars only to tune the handling characteristics. (Under and over steer) the more torsion bar spring rate the less sway bar correction for roll and tuning needed.

IMO. Increase the torsion bars a little and only change the sway bars if the ones you now have are not adjustable.

Edit,
John is spot on and brings up a good point not addressed in you questions and one I neglected as well. I instruct and Tech for PCA Potomac and we allways recomend that you start learning with a car that is as close to stock. As you learn the car will "tell" you what you need to do to change the handling. My pet peve is big fat sways installed only because the owner was able to handle that and T bars were too hard to do. Porsche built well made cars that realy only need changing if we plan to use them for other than originaly intended.

[widebody911]

Holy cow, bushings for $1000? I'll do 'em for half that!

If you're going to take it apart far enough to do bushings, replacing the torsion bars are an obvious 'while you're in there' job.

If you upgrade to bigger sway bars before bigger torsion bars, you run the risk of ripping the mounts out. That's what happened to me.

[avi8torny]

I think you are well on your way to having a great setup for the occasional DE. I did everything you did plus last winter I replaced all the bushings with plastic. If I had it to do over again I would have used the neatrix in the rear. They don't make replacement rubber neatrix for the front. The one thing you will have to do with the plastic bushings though is to slightly machine them to make them fit properly or else they will bind and squeak. Shops will do this for you if you ask but remember...you pay by the hour.

While you are in there, buy a used set of Torsion bars like the 22/29. The won't degrade the ride at all and it will handle better..much better. I went with 23/30 hollow in the targa which works great for me....not hard to do if you have the time and good working space.

I did NOT change my sway bars and feel that the stock one's are perfectly balanced with this setup.

If you are going to do the rear spring plate bushings, I would recommend replacing the banana or trailing arm bushings with the OEM parts not the monoballs. When I took mine apart the rubber practically fell apart in my hands. They will cost you about $80 from the dealer and you will need 4 of them....2 for each trailing arm. Well worth the investment.

Keep us posted.

[Superman]

I'd agree that seat time is more critical than all those suspension issues put together. Stiffer torsion bars will improve handling pretty painlessly. I am not a sway bar man. I'll admit their adjustability is very nice when sorting out the car, making it handle neutral. Stiffer sway bars without first installing stiffer torsion bars is a grave mistake. It will make your car handle more poorly, and will also result in some offensiveness in ride characteristics. I think you would deeply regret plastic suspension bushings, but who knows, maybe not. They are hard as rocks and cracks in the road will feel like hammers against your frame. Neatrix bushings are the way to go, IMHO.

Sport shocks are also a good idea, particularly if you are going to stiffer torsion bars. So, I think it is:

1. Shocks
2. bushings
3. torsion bars (along with the bushing replacement
4. sway bars (adjustable ones, if you must)

So, I guess I disagree with the folks who place sway bars in the #1 position.

[rdane]

Thanks a bunch guys! Glad I wasn't totally off in what I had been thinking with bushings first then Tbars.

I did put on Bilstein sports and changed the tires to 225 fronts and 245 rears (previous were same tire and 205/225). With new shocks and tires the car went from a fair amount of understeer on the skid pan (no spins in the pouring rain) to a fair amount of over steer on the street. No problem whipping the rear end around a corner now if I like.....which I am not sure I do like. Skid pan would be WAY different now!

Going to take another DE day to make the decision if that is good or bad. I was told a little over steer is good today. What do you think on that one?

Sounds like Sander's bars and bushings. Any idea what that will do to handling?

Wings? Don't have one and have spent a reasonable amount of time around 90 and 100mph and have yet to feel the back end is loose when the car undertsteered. Is that going to change as the car is set up now? Do I want/will I feel a wing?

[89911]

I have replaced every bushing in my car with poly and I have never really had a problem with ride quality and noise. I took a lot of care in fitting these with the proper conformity, maybe that is why. The rears have not been a problem over the past 3 years. The front A-arms groan a little when starting out, but that is about it. As far as when you should do the improvement, maybe I should ask, " When do you want your car to start handling better!" Trust me, it doesn't take long to realize you standard suspension is too soft for serious track use. Go 22/29 with the t bars. I run 22/30 with 27mm hollow sway bars, reinforced at all the body points.

[89911]

Originally posted by avi8torny
I .


I did NOT change my sway bars and feel that the stock one's are perfectly balanced with this setup.

Are you nuts? Your torsion bars are almost twice the size of those itty bitty stock ones. Since you've stiffened the suspension exponentionally with the bars, how do you expect the amount of force that the sway bar transfers to the other side of the suspension is going to do anything?

(I know Tom. Just justifying my 27mm sway bars!)

[Green 912]

More Tbar = less swaybar! Swaybar is for tuning not corecting problem setups. Standard practise is, given a set car weight, as you increase the T bar you should decrease the sway tension as it is undesirable and less required.

89911, it's OK you can keep them, just set em' out.

[Randy W]

I've listed this before on other similar threads - Here is the order in which changes are made by the best suspension guys I know:

1, Springs (torsion bars and tires) - depending on track and conditions
2. Shocks - matched to the springs selected, surface, and transitions.
3. Sway bars - for fine tuning according to driver style.

Tire choice is listed with torsion bars as their effect is extremely important and they act like springs dependent on sidewall height. Alignment is obviously important along with a weight balance and must be done for optimum tire contact patch dependent on speeds and transitions expected. Bushings/monoballs simply allow all the above component to work optimally and improve driver feedback - a full cage is similar in its effect. Turbo tie rods, strut bars and the like also have a similar but much smaller effect.

[APKhaos]

Guess you see that there is a consensus here - Randy summed it up best IMHO.

Also happens to be the order in which I did mine. Making these changes in phases [TBars & Bushes, revalved shocks, sways] really adds value in that you will understand the new characteristics at each stage, and gain a far better appreciation of suspension dynamics as a result.

Its not clear if this is your first DE season, but if it is you can learn a LOT driving the stock setup. At the max, you might consider Tbars and bushings & maybe shocks, just to overcome the slop that is sure to be there in your current rubber bushings. Street Poly bushings really worked well for me - no added harshness.

Seat time and instruction are the best bang for the buck - by an order of magnitude!

[jluetjen]

Since you've stiffened the suspension exponentionally with the bars, how do you expect the amount of force that the sway bar transfers to the other side of the suspension is going to do anything?

Actually sway bars don't transfer weight from side to side -- they transfer weight from end to end. So in a right hand turn, a stiff rear bar will transfer weight from the Left front corner to the left rear corner (less any chassis flex). A similar affect can be achieved by using stiffer rear springs in the rear. The difference is that the springs will stiffen the car in 2 wheel compression also (for example when squatting under hard accelleration or when the suspension is compressed while crossing bump that spans the car) while the stiffer rear sway bar will not have this affect.

The popular opinion is that 911's need stiffer springs (T-Bars) prior to stiffer sway bars. My own personal observation is that many people left to themselves will overspring a car. Since I haven't tracked my 911 yet I haven't had a chance to test this and develop my own opinion. (Note that have raced other cars though.) But I do tend to have a healthy skepticism of "conventional wisdom" for no other reason then that following it provides no advantage beyond the norm. I just have this mental image of lemmings marching off cliff.

I tend to agree with Randy, but I'd like to add that I think that his point assumes that the car's suspension is already "up to spec". The reality is that bushings often wear imperceptively during a car's life. But once you take a 20 year old car on the track you may possibly find all sorts of wierd behavior if they have worn out of spec. This is the only reason that I put bushings first. If you car is up to spec (none of the components worn out of spec), then I think that Randy's going down the right path.

If I could be so bold, I would like to add a point 0 to Randy's list though -- tire pressures. The car is only held to the road by the tires. I have found that the most drastic affect to a car's handling can be achieve with only 1/2 a pound of change in a car's tire pressures. In fact this is the primary tuning method for Showroom Stock race drivers whom generally can take a showroom stock car's performance to a level that would astound most non-racing drivers. If adjusting the pressures (and as a result the temperatures) does not solve your problem, then I would agree to start down the list that Randy suggests.

[Randy W]

John, you bring up some good points. Tire pressures are important and should be checked after every run or session at the track. Although they do influence spring rate somewhat, pressures are really more tied to weight, alignment, track conditions, and driver style. Once all the other suspension variables I listed are upgraded, assuming that the rules allow it, more attitude can be adjusted into the car via shocks and sway bars than can be adjusted via tire pressure. Given the ability to adjust these other variables, most competitors only change tire pressures from their optimum settings for that particular tire/car for changes in track conditions (heat/rain/rubber build up) than for anything else.

I did not mean to imply good bushings are not important, I simply wanted to clarify that upgraded bushings are not as important as most people think. For most people with mild suspension upgrades, bushings have a job to do and that is to keep that $150 alignment in check. In my blue '72S with 72K miles I have OEM rubber bushings throughout - most of these are original and 30 year old, they still allow the car to be driven comfortably over long distances, and I've won about 20 autocrosses with this car over the past four years. In my white dedicated autocross/DE white '72 RS look I have added front monoballs and replaced all the bushings (except the inner trailing arm) with Weltmeister ones and they do exactly what I needed them to do - keep all those expensive components working at their optimum and improving driver feedback, at the expense of lots of harshness and noise.

I agree with you John that overspringing a car is a danger for many. Interestingly, for a pure track 911 lots of people have found that a big enough torsion bar is not available for the rear, so they go to coil-overs if they can. In my experience there is maybe a greater danger of using too stiff a sway bar. With less and less compliance coming from modern tires with shorter sidewalls, there is a real danger of reducing compliance to the point where the car cannot use all of the suspension that is being thrown at it, especially on a bumpy track. This is a very interesting thread and shows just how many variables are invoved and how much of a journey it is to getting a car set up "just right".

[69911e]

John is right(as are all 69 911E drivers); I found most people follow each other(right or wrong).
The goal of suspension design is to be as compliant as possible, not as stiff as possible.
When tuning these are my guidelines.
Springs should be just big enough to keep suspension geometry within desired specs in bump.
Sways should be just big enough to keep suspension geometry within desired specs in full cornering.
Shocks just big enough to keep tires in contact with the ground.
Remember other correctly tuned cars which have a wider or narrower track and wight should not necisarily have the same suspension parts as you.

[pwd72s]

Randy? Maybe Evren will weigh in if he reads this, but he is very happy with the suspension set-up you suggested on his 911E. I just wish he'd driven it when I did...before the mods were done. I think he'd be deliriously happy! With no sway bars, stock torsion bars, it handled like a '56 Buick...

[Randy W]

Paul, glad to hear that set-up met Evren's proposed needs. Ed is right of course (as are all early 911 drivers - toungue seriously in cheek ), compliant as possible for your needs is the key. My two early 911s are set up entirely differently - the white car is more capable, but the blue car is more fun...

[racemor]

This is a really good thread for me right now as I am planning to revamp my suspension this coming year. Randy makes a good statement:

"shows just how many variables are invoved and how much of a journey it is to getting a car set up "just right"."

These variables can also make it really easy to screw up the handling of our cars that the factory engineers spent years getting right. While I know that these things can make them better, getting the combination right is what matters. What is a good starting point? I know that it is dependent on the power your car makes, various tire and wheel combinations, etc. I was planning on using the specs used for the '73 RS as a basis for torsion and sway sizes for my stock engined, narrow bodied car. Is this a good starting point?

[jluetjen]

I was planning on using the specs used for the '73 RS as a basis for torsion and sway sizes for my stock engined, narrow bodied car. Is this a good starting point?

racemor, I think that that would be a good strategy. I would then evolve it from there based on your own particular needs. As I mentioned earlier, after you are capable of lapping the course consistantly is a good time to start thinking about changes. At that point I'd start thinking about what parts of the course I want to improve and how can I change the the car to do that. If you're making changes before the driver is consistant, you'll never know if the results were due to the driver or the car!

I've found that just because 2 drivers achieve the same performance, they may not do it the same way. A famous example were Alain Prost and Ayrten Senna. Prost would "drive with the front of the car" and liked a car that had a slight degree of understeer. Senna "drove with the back of the car" and generally had a little more oversteer dialed in. I've read that their car set-up's would often be significantly different. But yet both of them might be within a 1/10 of a second and find the other's car to be virtually unraceable.

[Randy W]

Well, there has been some confusion in books regarding this but my research indicates the '73 RS touring had the same brakes, torsion bars and sway bars, as a '73E with S package. The only change was from Koni to Bilstein shocks. Some of the '73 RS lightweights (sport) and factory race cars of that period also used 19/26 torsion bars and 18mm (or 19mm) through the body type sway bars - which is a good place to start I would think.