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620 sway bars


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Ok, here is an old update. Installed a rear sway bar from a Nissan Pathfinder. Guessing that it was about a 1990 model. Was from a 2 door Pathy, not the later 4 door. I dont know if that matters though. The bar was a freebie, so i thought i would try it. I purchase axle saddles for trailer axles from the local steel/trailer fabrication shop and added a couple of holes. Angle cut the ends so they didnt look so bulky, then welded them to my axle housing. Sorry, no pic of this. I didnt like how the sway bar angles came out with the pathfinder end links, so i found some shorter ones from a Nissan Sentra(93). I made a mount to weld to the frame near the spare tire for the end links.yello620003.jpgyello620006.jpgThis sway made a HUGE difference in how the truck drives.

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Find an earlier 620 in the yards to get the one for the front. 

Rear will be a bit more custom. 

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Seems like pre '77s had them stock. When they went to ball joint suspension/steering they droped it and it was then only optional from '78.

 

Adding or stiffening a front sway bar  will add understeer to your vehicle. A small amount of understeer is built into your vehicle to begin with as it's presumed to be the easiest to recover from by letting off the gas and applying the brakes. Not much sense making it worse.

 

Adding or stiffening a rear sway bar decreases oversteer so it would be advisable to add or increase rear sway bar if adding to the fronts to remain neutral.

 

In many cases people add them without knowing why except that race cars do it to improve handling. It does, but it's much more than that. Blindly adding one can ruin the handling

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Here is a wordier version of what Mike said:

 

"Tuning advice

Just like spring rate, you want to run as soft an ARB as possible while maintaining sufficient control of the car and body roll and the proper handling balance. Softer settings lead to more compliance and more grip on that end of the car. They also tend to be slower responding and easier to drive, but stiffer settings can be more stable and faster responding.

 

Front:
(1) Stiffer: Will increase overall car stability (reduces roll) and shift the car’s balance toward UNDERsteer (push), thus allowing the driver to be more aggressive with the steering. The compromise can be on bumps and/or braking. A stiffer front bar will reduce compliance, so when one tire hits a bump the entire front axle will be affected through a loss of overall grip.
(2) Softer: Allows more roll and will shift the cars balance toward OVERsteer (or less UNDERsteer.) And the front will improve in compliance, which improves performance in brake zones and over bumps.

 

Rear:
(1) Stiffer: As you add throttle through the corner while the steering wheel is still turned, the rear anti‐roll bar becomes very effective. Stiffening the bar supports the rear and shifts the balance to less UNDERsteer at corner exit. Again, the compromise is in compliance; a possible SNAP or FLAT OVERsteer may result if rear anti‐roll bar is TOO stiff.
(2) Softer: Allows more roll at the back of the car, which will be most evident at corner exit. If the bar is TOO soft, the car will exhibit exit OVERsteer. In this case, compared to a rear bar that is TOO stiff, the exit OVERsteer condition will be more gradual instead of a snap, hence the phrase “roll OVERsteer.”

 

Interactions

The roll control effects of an anti-roll bar or sway bar are similar to the effect of changing spring rate (in effect an ARB is just a special kind of torsion spring), thus the roll stiffness of the ARB is often traded back forth between spring rate to determine the optimum compromise. Stiff front anti-roll bars can also lead to increased front inside front tire lockup under braking."

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addco makes a front 1" bar and a 3/4 rear

 

YEAR     STOCK #front     DIAMETER     ENDLINK KIT       NOTE #        STOCK #rear          DIAMETER          ENDLINK KIT NOTE #

 

To 76

             887                 1″                    015                   13                               228                       3/4″                        015
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Lets say it may be a starting point but there are many many variables like springs, vehicle height, shocks, tires and rims, wheel base and wheel tread. Sway bars have to balance with each other as well. Simply throwing on a rear bar can drastically add severe understeer to the front.The vehicle will plough straight ahead instead of turning.Increasing the front bar increases the oversteer and the back will slide out on you in a hard corner. Often you never drive this hard to find out, but poor traction events like rain, snow or gravel will give you a surprise. Use with caution.

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Klassic; where did you find that info. Thats good stuff.

I can't find it at the moment.  You can google "the effects of anti-sway bars" if you want to find more.

 

1" up front and 3/4" in the rear seems to be a standard for most front engine RWD vehicles.

 

Lets say it may be a starting point......

I agree, I was just making the realization that I see that combination offered by the aftermaket for most vehicles.

 

I don't disagree with "proceed with caution". But at the same time, the best way to find out if a certain setup will work for your driving style is by trying it.  I would make the assumption that using a stock bar designed for the earlier 620 would work pretty well.  I'm not sure what size the Pathy rear anti-sway bar is, but if it is bigger than 3/4", then I would question the outcome.

 

 

And if it wasn't explained enough already, this one gives a good explanation:  http://www.autocross101.com/Sway_Bars_101.html

 

what is a roll bar

The anti-roll bar is essentially a transverse-mounted torsion bar designed to reduce body-roll during turns.  It exerts no influence on the suspension when wheels bounce in unison.  If vertical movement on one side exceeds the vertical movement on the other, the anti-roll bar exerts an opposing force.  Along with its primary function of reducing body-roll, the anti-roll bar will also reduce the combined cornering force and the adhesion limits of the side-by-side tires that are being acted upon.   Consequently, the location and stiffness of the bar can be modified to influence the oversteering or understeering characteristics of the vehicle.

 

Body Roll is reduced by torsional effect of sway bars as they transfer the pressure exerted on the inboard wheels. The weight is more evenly distributed to all four wheels helping the vehicle stay more level with the road and improving control in turns.

 

What is the purpose of sway bars? They tie the left side wheels to the right side wheels on both the front and rear of your car.

What do they do: In a corner your vehicle wants to roll over in the corner due to centrifugal force.

With out sway bars on an off-road vehicle this causes excess chassis roll that compresses the outside suspension and tire and causes the inside tire to go into droop.

While on an on-road car this excess chassis roll overloads the outside tire and unloads the inside tire lowering overall traction.

on a car or truck a sway bar accomplishes the same thing, but the big difference is that on a car on road racing, it keeps both the inside and outside tires planted squarely on the ground increasing traction, by allowing the suspension (leafs or shock) to apply there forward traction in a corner and here is were a posi rear end also comes into play

The weight of your car or truck also determines the size of sway bar you need to run. A heavy monster truck with heavy large tires will need a large heavy sway bar. While a small light weight on-road car will need a much smaller lighter one.Also to keep in mind with learning how to adjust and tune your sway bars is your setup and driving style.

You may want to run different size sway bars on the front and rear. There is no carved in stone rules when it comes to sway bar adjustment. It all depends on your conditions and driving style.

Keep in mind that your sway bars do not work by themselves. The effectiveness of the sway bar you run depends also on the weight of spring you run.

With the sway bar tying both the left and right side together, the sway bar must overcome the weight of the spring on the opposite side as one side compresses.

If a light weight thin sway bar is used this allows a lot of movement on the outside suspension arms and very little on the inside suspension arms in a corner.

 

While a thick heavy weight sway bar so stiffly connects both sides of your suspension resulting in what feels like a straight axle suspension.

The trick is finding the sweet spot between these two extremes. Sway bars do not change the overall traction of your rc car or truck, they just affect your side grip in a corner.

Besides springs chassis flex plays an important role in the effectiveness of your sway bars. The stiffer your chassis is the more responsive your car or truck will be to nay changes to sway bar settings.

Adjusting sway bars is a balancing act, increase stiffness to a sway bar on one end, reduces the side grip of that axle, while increasing the side grip on the other end.

The net effect of sway bars on both on-road and off-road vehicles is almost the same.

 

A softer front bar:

1. Increases front chassis roll.

2. Increases front grip or traction, while decreasing rear grip or traction.

3. Slower steering response.

4. Increases off-power steering at corner entry.

A stiffer front bar:

1. Decreases front chassis roll.

2. Decreases front grip or traction, while increasing rear grip or traction.

3. Faster steering response.

4. Decreases off-power steering at corner entry.

A softer rear bar:

1. Increases rear chassis roll

2. Increases rear grip or traction, while decreasing front grip or traction.

3. Less on-power steering.

A stiffer rear bar:

1. Decreases rear chassis roll.

2. Decreases rear traction, while increasing front grip or traction.

3. Faster steering response in high speed corners and chicanes.

4. Increases on-power steering.

 

SOME TECH STUFF

The stiffness of any torsion bar (and that's what an anti-roll bar is) can be approximated using this equation:

 

K = 1,178,000 x (D4 / LA2)

 

Where K = bar rate in lbs/inch D4 = diameter of the bar, raised to the 4th power, measured in inches L = center length of the bar, measured in inches A2 = lever arm length, squared, measured in inches and 1,178,000 is the rigidity modulus constant

 

When you are working with solid bars, D= the outside diameter (O.D.) of the bar. When you are working with hollow bars, D = the wall thickness of the tubing, NOT the O.D. of the bar.

 

So, if company "A" offers a 28mm. hollow bar for your car, and "B" offers a 28mm solid bar for your car, the solid bar will have the higher rate if the lever arm and center lengths are held constant. Do the math before purchasing a hollow bar. It may be lighter, but it's not as stiff as a solid bar if the O.D.'s are the same.

 

The stiffness of an anti-roll bar may also be calculated based on the torque force required to deflect the lever arm by 1 degree. The mathematical formula is different, and the unit of measure is Inch-pounds per Degree.

 

 

Side notes on front swaybars rates offered for stock subframe

Hellwig 1 1/8" tubular 600 lbs

Hellwig 1 1/8 solid 720 lbs

DSE 1 1/8" tubular 1532 lbs

Global West 1 1/8" solid 1279 lbs

Hotchkis 1 1/8" tubular 750 lbs

 

Rear sway bars

 

Hotchkis 3 way adjustable, 310 lb/in, 380 lb/in, or 490 lb/in effective rate.

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  • 7 years later...

My '78, also with ball joints, didn't come with a sway bar, but it is after all an option. I pulled one off another tuck and the threaded mounting holes were all there. Nothing wrong with a little less body roll.

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I sourced an aftermarket rear sway bar from RockAuto and scooped the last one. Kit was missing one bushing which they couldn't source so they refunded my purchase but I got to keep the kit. Measured it up and found a suitable replacement.😁

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