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Old 07-14-2003, 04:21 PM
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Sway bar logic

I just returned from the Columbus GoodGuys show and we had a debate going on about the need for sway bars. The arguements were one of three. First, only a rear sway bar is needed for rods with a new style IFS. Second, front and rear sway bars are best for any car regardless of type of suspension (except those suspensions that do not have a means to mount it) and Third, sway bars are best suited to cars that are experiencing tracking problems or extreme body roll. I want to reduce body roll on my 37 Plymouth sedan fitted with a Fatman Stage II IFS and do not know if I should get just the rear bar or both front and rear. What suggestions do you have to offer?

Swayman

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Old 07-14-2003, 06:08 PM
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Front and rear sway bars are a good idea for any car. Detroit doesn't use them on low cost cars to save money but that doesn't mean they wouldn't measurable improve performance. They work best (as all suspension parts do) with a very stiff frame. If you can still do it, box the frame rails along with adding sway bars.

On old cars I like to use Ford Courier pickup sway bars. See picture below. Add a 1/8" wall 1 1/4" square tube to frame, a couple of brackets on the axle and the Courier bar and hardware bolts right on.
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Old 07-15-2003, 07:05 AM
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Thanks Willys for the feedback and photo. I guess what you are in favor of having front and rear bars. I don't have the room to install the system you suggest because my exhaust pipes are in the way. I will look at other methods to add a rear bar. The frame is another matter. To stiffen the frame will be very difficult because the car is fully assembled. Could I stiffen the frame by bolting on additional steel? I could make a box section out of heavy gauge sheet steel that could be wrapped around the frame. It is not a pretty but might perform as well. What do you think?
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Old 07-15-2003, 07:23 AM
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No, I don't think a bolt-on box would be worth the effort. The IDEAL is a perfectly stiff frame w/ front and rear roll bars. No car is perfect but come as close as you can. Adding the bars will benefit regardless.
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Old 07-16-2003, 11:37 AM
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I think you would be suprised at how much just a front sway bar will do for reducing body roll. I would start there and you may not need to go to the rear.

There are some issues of physics to consider however. If you stiffen the front, it may tend to loosen the rear as far as cornering stability is concerned particularly if the rear has soft springs. I agree that a front and rear sway bar, tuned to the car is best, but not always necessary to get a significant improvement in handling. I use just a front sway bar because my rear springs are so stiff in my truck that they allow little roll anyway. The truck literally drives like a sports car.
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Old 07-16-2003, 03:28 PM
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My car weighs 1575 lbs in front and 1730 lbs in the rear. The body is not chopped.

The rep at Fatman told me the bar in the front is not needed with the typical Stage II package. He suggested a rear bar only. The rep at Chassis Engineering said the best is to have front and rear bars.

I'm new at this but my instincts tell me the higher and heavier end of the car is where the help should be, and that is in the rear. I have a better understanding of how to attach a bar in the rear thanks to Willys' photo.

I guess the thing to do is determine the best place and route for a bar and then go about the process of finding one to suit. Chassis Engineering offers various diameter bars. Any rule of thumb to get me started on how to determine which diameter will work best?
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Old 07-16-2003, 04:33 PM
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Well....... anytime you install a sway bar on a car front or rear it is going to improve the handling characteristics of the car. Now being that most front suspensions work on motion ratios and are typically heavier than the front, you are doing yourself a favor by putting one in the front. There is obvious exceptions to every rule but as a general rule of thumb you want to run one when available...........

Tony...
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Old 07-16-2003, 06:03 PM
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Well since the whole point of anti-roll bars is to improve cornering let me break it down a little more. If you are turning and not accelerating or decelerating, the amount of body roll is proportional to the weight distribution of the car. If for example you have a car with 60/40 weight dist. and only a front sway bar and take a hard turn without having to brake. Since the front end has controlled roll but the back end does not, the rear end will twist the car, also putting more roll into the front end as the body resists twisting.
Now when your racing and you enter a corner and brake, the car not only rolls from side to side but also rear to front, placing more stress on the front roll bar. Since this is the most likely situation (versus accelerating while turning ) and most cars are heavier in the front the front anti-roll bar is always a good deal larger. If the goal is to turn harder (faster) having anti-roll bars on the front and rear is of great benefit.
Even if your car is rear heavy you will definately benefit from a front sway bar.
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Old 07-16-2003, 08:40 PM
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jpd37: your car may in fact weigh more in the rear (I don't know why and would have guessed otherwise), but the facts are pretty well laid out by Johnny. The worst body roll you can induce is in a heavy front braking turn because this shifts the weight forward significantly. Even a hard turn without braking shifts weight forward because of the scrubbing action of the front tires causing weight transfer. This is where an anti roll bar helps, in the front. I think you may have gotten some poor advice from your vendor. He may be defending his product.

I have been road course racing for years and pretty well understand the principles involved. Even with a Porsche where the weight and traction bias is in the rear, the first sway bar goes in front. Ask any racer.

In any event, go to the wrecking yard and find a sway bar from an early S-10 or Ford (little) pickup, they are close to the right width and do a home fab and try it. If it doesn't work, take it off.
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Old 07-17-2003, 08:06 AM
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I put front and rear bars on the 36, very glad that I did. Prior to doing it every time a big truck passed me I could feel the car want to wander due to the air pressure on the car from the truck. After I did it I do not even notice it when a big truck passes, plus the car drives better and goes around curve without the body roll. I think the front is the most important but I did both. I used the Chassis Engineering kit which is straight across instead of having the big "U" in the front of a stock MII. My 2 Cents worth.
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Old 07-17-2003, 09:01 AM
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From all that has been said, I am convinced and will look into front and rear bars. I am trying to make the car as safe as possible to drive since I am doing a lot of long distance highway driving and want to feel reasonably comfortable and safe. For my situation w3hat diameter bar is most typical? I'm thinking minimum 3/4" diameter.

There is one more thing I have considered. Is it possible the rear springs could laterally deflect during a turn or in windy conditions on the highway? I am wondering if the rear springs laterally deflect then the body weight shifts and exagerates the side sway or roll effect. I have seen sway arms that mount between the rear axel and the frame to resist lateral movement, but typically on coil setups. Would this be a factor even on leaf spring designs?
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Old 07-17-2003, 09:06 AM
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You are right on track with your thinking...... Most typical diameters found would be 7/8- 1" in front and 3/4-7/8 out back. I couldnt see using any larger than that for a street diven vehicle. Chris Aslont chassiworks make a very cool torsional sway bar with billet end links....... a little spendy but a very cool piece..... Good luck with your venture!

Tony...
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Old 07-17-2003, 09:37 AM
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That lateral bar is called a panhard bar. I don't think you would see any difference with one on leaf springs which are quite stable in the lateral direction. In fact, the panhard bar swings through an arc as the springs deflect and would put undue side stress on the springs which want to go straight up and down. The only system that you could safely use on leaf springs is a watts linkage which prevents any sideways movement while not inducing a sideways arc of its own, yet allows free up and down movement. Not needed with leaf springs.
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Old 07-21-2003, 06:37 AM
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Thanks for the feedback. I was in Knoxville for the weekend checking out a 33 Ford under construction. I appreciate the info and will discuss my situation with Chris before I select the sway bars I'll use.
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Old 07-24-2003, 12:00 AM
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Definately get both front and rear anti-sway bars. Your car is not light and you need them to be safe. Considering this technology has been around for 45+ years, I don't understand for the life of me why any company would sell front suspensions without this vital part included , let alone for a streetrod, which automatically excudes performance and the average observer would expect superior handling in such a clearly altered-from-stock state. The auto manufactureres around the world have all but made anti-swaybars standard equipment on the vast majority of vehicles front suspensions since the early 1970's, often offering rears as optional. With the large wheel diameters and widths as on a typical streetrod this need is increased especially as weight increases. I wouldn't consider building a streetrod without a front antisway bar, it would be an insult to the car's image. And I would add a rear where-ever applicable. The last thing you want is lots of power with poor handing, that equals inevitable disaster.
I will not sway from this opinion,
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