Rear sway bar question

[polara71]

Thank You John, I got through half of that and my mind started to explode......

Good stuff there though every one here should read this

 

[Zymurgy]

Thanks for all the input guys. I did change the factory sway bar in the front and it now has a 1 inch PST set up.

Currently what I am trying to improve is the feel of the car in the corner. It feels very good turning into the corner, when I add some power I feel the rear twist and it feels loose. I am certain the addition of the rear sway will improve the overall feel of the car.

Unfortunately I never knew what the factory front sway bar felt like with the rebuilt front end, because I did it at the same time. I am certain what I have is an improvement over the factory, so I feel the addition to the rear sway bar will compliment the new front.

 

[Big_John]

When my sons and I were doing some autocrossing with the Neon, we added some huge hollow sway bars (front and rear) and got the roll stiffness so tight that the car would pick up the inner rear wheel on a hard corner. Note the air under the right rear tire.

 

[1978 NYB]

Since we are talking about sway bars.....

Anyone know of a part number or manufacturer for a Formal front sway bar mounting bushings?

I know AZ has universal mounts available.

 

[saforwardlook]

This is a very complex subject. That was the number one "take away" from my discussion with the suspension engineers. There are so many factors that affect the drivers' perception of a soft comfortable ride balanced with a steady feel to the car with minimal sway on bumps or turns and expected accuracy of tracking through a corner when turning the wheel.

There are a huge number of factors that affect all this. Recall the bias ply tires were the norm with disadvantages compared to radials. Then there were torsion bars up front and leaf springs in the rear on Chrysler products, while GM used all coil springs back in the 70s. Then there were shock absorber settings and those could vary front to rear, with again the emphasis on a smooth ride. Then there were weight distribution issues. Also to consider was safety. In the U.S., most of the cars were front heavy compared to the rear, which tended to make a car plow through turns. The obvious solution was to add a rear sway bar as one option, but doing so could compromise safety. U.S. drivers tend to brake going into a corner and turn more to keep on track, but adding a rear sway bar can cause a car to more likely swing out in the rear leading to accidents - powering through a turn with a rear sway bar would lessen this, but few U.S. drivers at least, are likely to do this. Lawsuits were to be avoided at all costs, so rear sway bars were added with careful consideration. Front sway bars lessen sway of the vehicle, but worsen plowing - adding a rear sway bar can lessen this but with safety considerations.

It is kind of like adding a performance cam to an engine and then expecting a large increase in acceleration and power, but often times one ends up with a sluggish car that performs more poorly than stock unless a bunch of other things are done to make the powertrain work as an optimum system - the need to consider torque converter stall speed, rear axle ratio, air/fuel ratio adjustments, timing adjustments and so much more to end up with what you were going for. So it is with adding a rear sway bar - it is important to know what you are doing to end up with a well balanced and safe handling vehicle. Both powertrains and suspensions are designed as systems, and require consideration of all the multiple variables when setting out to improve the performance or handling. I agree that the important message is to balance the upgrades and not strive for single large steps without understanding exactly what you are giving up when trying to improve one performance aspect.

Nonetheless, everyone "knows" that adding a performance cam and adding a rear sway bar will fix all your problems - just ask the guys selling the stuff. Often, just the opposite is the result. That is why engineers are needed to do the systems engineering once the most important goals are set to achieve and the tradeoffs that can be accepted are decided.

Steve

 

[Zymurgy]

Thanks for the advice. Well I am willing to be the guinea pig here and I give a full report.

By the way what is the fun in the corner if you don't try get your car set up to at least attempt to power on through it. This is my main objective in the first place.

 

[tbm3fan]

I didn't see it anywhere so what is the size of your front and the size of the rear?

 

[bajajoaquin]

When I worked at Chrysler Engineering starting back in 1969, I did investigate putting a beefier sway bar on my newly acquired 70 300 coupe. I talked with the suspension engineering guys about this installation, and they said that use of a beefier sway bar on a C body coupe especially was not necessarily a good thing, since it made the car plow in turns more than the standard front sway bar. Rear sway bars were used on the 4 door sedans as an option to improve this plowing tendency if special ordered, such as the police units, as I understood them at the time, but even there, they were not overall that much more helpful they said. It was partly a weight distribution thing too as I recall. As it was, they were struggling with rear wheel hop with the leaf springs on the coupes under panic braking conditions in part for the same reason.
Steve

(edited to add: to be clear, I think Steve is spot-on here. The following is not meant to sound like a contradiction)

My recollection from racing is that it's a bit counter-intuitive. More bar makes that end flatter in the corners, but does so by putting extra load on the outside wheel, causing less overall cornering capacity.

The money section of that link seems to be:

The primary function of the anti‐roll bar is to adjust the understeer/oversteer balance of the car during cornering, which it accomplishes by fine‐tuning the amount of load that transfers to the outside tires at the front versus the rear. A stiffer anti‐roll bar at one end of the car will increase the load on the outside tire at that end. If both bars are made stiffer, the load transferred will remain the same, but overall chassis roll will be reduced, which may require a camber adjustment. Remember, one of the primary goals is to find a good balance between grip at the front and rear of the car.....

If you increased the roll stiffness at the front of the car by adding a thicker bar, in order to bring the back of the car in balance, you would want to add some roll stiffness at the rear of the car as well. My nickle would suggest that, in this case, the thinner PST bar would be the place to start. But either way, it's something you should talk to Firm Feel about and make sure that you're getting something balanced, not just big.

 

[Zymurgy]

The front bar is one inch. The feel firm rear is 7/8. The feel firm has 1 1/8 and 1 1/4 bars for the front. Not planning on changing the front.

Order placed, if on shelf ships immediately, if not 10 days.

 

[bajajoaquin]

That sounds like a good place to start.

Taking this back to a general question about "should I add a rear bar?" it seems like the answer would be "not unless you've added a bigger front bar. Which then begets the question: should I add a bigger front bar?

Steve made a comment about using bias-ply tires as OE in his post, and the link talks about needed camber changes. One of the big differences between radials and bias-plies is the stiffness of the carcass. Radials are much softer (this is why radials tend to have lower sidewall aspect ratios).

On the 235/75-15 that is very common here, I'm going to guess that the sidewall would flex much more than the old bias tire that was originally on it. Therefore, you would want to reduce body roll to keep the tire more vertical (less camber change). So if you wanted to take advantage of the handling improvements of the radial tires, then, you would want to add more bar front and rear.

Someone here also posted advice for changing the alignment specifications to accommodate radials. I'm positing that both of those changes could be done to good effect when you switch to radial tires, and it would improve the ride and handling without necessarily changing the "character" of the car.

 

[Zymurgy]

Well I took a day off work today and installed the feel firm rear sway bar. Direction not too great and had some incorrect info, but common sense made the installation a relatively smooth. It did take most of the day.

It is a well engineered bar. Tomorrow will be the test drive.

 

[Cbodyuser]

Well?? How does the car drive now with the rear bar? Where's the update?

 

[Zymurgy]

I wish I had an update. Unfortunately I have had fuel delivery issues that I was working on at the same time. I still haven't had a test drive.

I believe I am nearly there, depressing to think I did not drive her a single day in May.

 

[Zymurgy]

Finally a test drive. I could not be happier.

1. The car is amazingly flat in the corners. I can power out of the corner and it is solid as a rock. Big difference.

2. At high speeds (over 90mph) solid. Before it would feel like it is as kind of floating.

3. When driving over a short bump as speed, the rear tires would seem to leave the road and hop. That feeling is gone.

4. This has all been achieved with no change in the overall comfort that I enjoyed before I installed the bar.

5. Would definitely recommend, but not if any other areas need attention first.

Extra info. The other areas I would do before the rear bar. Complete new front suspension with 1 inch front sway bar. New stock style shocks (not the expensive ones). New leaf springs 1 inch higher than factory. Rebuilt steering box with "sport" option.

 

[saforwardlook]

Sounds really good and some good advice too on making sure the rest of the suspension is up to snuff. What was the front sway bar diameter on your car originally - 7/8" or ?? Do you think the new rear springs with a 1" higher stance helped some of this improved feel too - in other words, did you do the springs and rear sway bar together or separate to evaluate?

Did Firm Feel rebuild your steering box too or someone else? I had some problems with their rebuilt steering gears in the past and have switched to Steer & Gear, but maybe Firm Feel has upped their game a notch?

This is really good input and I will probably be making the same changes to some of my cars too to improve stability and cornering. Thanks for keeping us updated.

 

[Yatzee]

I put one of these on my C-body and you really need to give this a bit of thought before installing. First, the links should go in front of the axle and be exactly verticle on installation. When these are installed properly, the downward/upward force is perpendicular to the springs exactly the way they should be. When you mount the sway bar on top the stand-offs you will notice it may be on the short side to reach the frame rails. Again the sway bar must be parallel to the springs as much as possible. I refused to drill into the bottom of the sub frame as I could see there wasn't a great amount of thickness here and had visions of frame distortion or just plain ripping out. Either case, the bottom curved metal of the frame would be seriously compromised by drilling holes - just the right place for cracks to start in the frame rail. I took pieces of stiff cardboard and bent them to get patterns for U-saddles to bolt to the sides of the frame rails. Leaving the legs of these templates fairly long, I was able to move the U-templates in or out to support the sway bar rear swivel mounts at exactly the right spot to maintain parallelism and have the drop links verticle. The U-channels were then trimmed and bolted through the sides of the rails and the sway bar swivel mounts bolted to the face of them. That was two years ago and general inspection shows no negative results doing it this way. Be sure to use a minimum of 14g metal if you do it this way. You will notice when bending the templates that the frame tapers slightly but any good metal shop can bend and supply them cheaply. Mine were $20 the pair and fit perfectly as the shop used my U-channel templates. These sway bars work fantastic when installed properly but as stated earlier the front links must be verticle and the sway bar return links parallel to the springs with the car sitting on it's tires, not jacked with the axle dropped.

 

[Zymurgy]

Sounds really good and some good advice too on making sure the rest of the suspension is up to snuff. What was the front sway bar diameter on your car originally - 7/8" or ?? Do you think the new rear springs with a 1" higher stance helped some of this improved feel too - in other words, did you do the springs and rear sway bar together or separate to evaluate?

Did Firm Feel rebuild your steering box too or someone else? I had some problems with their rebuilt steering gears in the past and have switched to Steer & Gear, but maybe Firm Feel has upped their game a notch?

This is really good input and I will probably be making the same changes to some of my cars too to improve stability and cornering. Thanks for keeping us updated.

The front suspension and sway bar were big the steering box the biggest because of its poor state. I used steer and gear. Original 7/8 front bar one inch from PST. Leaf springs done 2 years ago. A member Dave recommended the 1 inch higher leaf, as much of a reason that you can load that cavernous trunk and if you lower it an ich from weight your still good. Plus I hate bottoming out the rear. It has never occurred with the new ones.

 

[SF-66TC]

I put one of these on my C-body and you really need to give this a bit of thought before installing. First, the links should go in front of the axle and be exactly verticle on installation. When these are installed properly, the downward/upward force is perpendicular to the springs exactly the way they should be. When you mount the sway bar on top the stand-offs you will notice it may be on the short side to reach the frame rails. Again the sway bar must be parallel to the springs as much as possible. I refused to drill into the bottom of the sub frame as I could see there wasn't a great amount of thickness here and had visions of frame distortion or just plain ripping out. Either case, the bottom curved metal of the frame would be seriously compromised by drilling holes - just the right place for cracks to start in the frame rail. I took pieces of stiff cardboard and bent them to get patterns for U-saddles to bolt to the sides of the frame rails. Leaving the legs of these templates fairly long, I was able to move the U-templates in or out to support the sway bar rear swivel mounts at exactly the right spot to maintain parallelism and have the drop links verticle. The U-channels were then trimmed and bolted through the sides of the rails and the sway bar swivel mounts bolted to the face of them. That was two years ago and general inspection shows no negative results doing it this way. Be sure to use a minimum of 14g metal if you do it this way. You will notice when bending the templates that the frame tapers slightly but any good metal shop can bend and supply them cheaply. Mine were $20 the pair and fit perfectly as the shop used my U-channel templates. These sway bars work fantastic when installed properly but as stated earlier the front links must be verticle and the sway bar return links parallel to the springs with the car sitting on it's tires, not jacked with the axle dropped.

Yatzee, a little difficult for me to visualize what you're explaining. Could you possibly provide some pics similar to Zmurgy's so we can see the difference and what you are referring to. Thanks in advance!

 

[CanCritter]

x2 on the pics if possible...not a fan of drillin frame at that point..definite stress point