Rear sway bar.

[hrspwr]

Yeah, you're liable to read all kinds of mis-information on that subject. Anyway, here's my experience, rear sway bars are meant to limit the amount of body roll and do a great job of it. I would never again own a vintage Mustang without a rear sway bar, they are that good. I'd love to take someone who thinks they cause oversteer for a ride in my car, it corners extremely well, yet sticks like glue, with not even a hint of oversteer. Also, if they are so horrible, why do prety much all new cars come with them? To each his own, but until someone can really show me a car (any car) that works better without one, I'll stick by my experiences.

All I can add to this is that I upgraded the front bar and added a rear bar, and my '66 handles great.

 

[Edster]

Thanks for all the info!!! I didn't want to start a fight!!! Seems like to me that leaf springs may need a sway bar to control the warpage. Its how i pictured it in my mind. Wouldn't a " neutral" between oversteer and understeer be the most desirable? Have the car when you want it where you want it.

 

[jlangholzj]

Thanks for all the info!!! I didn't want to start a fight!!! Seems like to me that leaf springs may need a sway bar to control the warpage. Its how i pictured it in my mind. Wouldn't a " neutral" between oversteer and understeer be the most desirable? Have the car when you want it where you want it.

pretty much, although it does slightly depend on driving style as well...usually you NEVER want understeer for competitive driving but if you do, and you know the limits, its workable. Also sometimes a little bit of oversteer can help you as long as you know how your car handles. Generally you want it somewhere right in the middle and really I don't think you're going to notice a little bit of oversteer as much as some of these guys are cranking it up to be.

The live axle does help somewhat with weight distribution but there is still lots of performance to be gained by adding a rear sway bar. Even though there's already a "bar" across with the axle, there's still no relation to the frame from the axle other than the suspension components.

really unless you've been driving dump trucks down a race track....you shouldn't think it "oversteers" too badly.

 

[Hack]

Thanks for all the info!!! I didn't want to start a fight!!! Seems like to me that leaf springs may need a sway bar to control the warpage. Its how i pictured it in my mind. Wouldn't a " neutral" between oversteer and understeer be the most desirable? Have the car when you want it where you want it.

Yeah I wasn't originally trying to start a fight on here either, but some people seem to be really strong advocates of rear sway bars and seem to want to attack if anything negative is posted about rear sway bars. I think if your car understeers a lot and you want to improve the cornering balance a rear sway bar is a great idea. But I think you should base the decision on how your car drives now, not on some "internet expert's" opinion. That's why I was trying to post general information rather than directly telling you whether or not you should put a sway bar on your car.

Yes neutral or as close as you can get it is good - if you are going to be in a performance driving situation and you take the time to gradually explore and learn the capabilities of your car in a safe way.

If your car is set up very well you will be able to balance it between over and understeer at the limit by using the throttle. The way I would say it is this: with a well-setup suspension (at the limit of traction in a hard corner) you can step slightly on the gas and the front will start to slide, let off the gas slightly and the back will start to slide, or at a neutral throttle setting all four wheels can be made to drift. Due to weight transfer you can manipulate which end of the car will stick better with the throttle. When you push a little on the throttle more weight goes to the back tires and helps them grip. When you let off the throttle more weight goes to the front and helps the front grip.

This is where "trailing throttle oversteer" comes into play. A non-expert driver is coming fast into a corner. They realize they are going too fast while in the middle of the corner and let off the gas. Then the weight of the car transfers to the front and the back tires let loose. The car spins or slides backward into the wall. This is a potential danger with a neutrally balanced car, and this is why car factories set up all cars to understeer still today.

I'm not saying classic Mustangs are dangerous or anything. I'm just trying to explain how front and rear swaybars work. I will try not to lose my temper again and go after anyone for mocking me or making incorrect statements.

 

[robbz28]

So let me get this straight...if i put a rear sway bar on my car, it will explode? Damn....

j/k

 

[Smitten65]

Only when you spin out backwards on corners and hit the wall with your gas tank ruptured by the broken sway bar!

 

[ace_xp2]

The live axle does help somewhat with weight distribution but there is still lots of performance to be gained by adding a rear sway bar. Even though there's already a "bar" across with the axle, there's still no relation to the frame from the axle other than the suspension components.

It's the leaves themselves that generate anti-sway, and they do it precisely because there's a "bar across". When both wheels lift the leaves will experience compression but no warp, generating one rate. When one wheel lifts the leaves experience compression and warp, generating a new, larger rate.

 

[jlangholzj]

It's the leaves themselves that generate anti-sway, and they do it precisely because there's a "bar across". When both wheels lift the leaves will experience compression but no warp, generating one rate. When one wheel lifts the leaves experience compression and warp, generating a new, larger rate.

The torsion you're talking about in the leaves isn't nearly as large as you think it is and i doubt that it would have enough effect in order to act like a swap bar. Torsion in itselft is an applied torque at a radius over the moment. Both the radii of that application and the moment of the square springs make a pretty negligible effect. Vs spring rates being an applied force per distance, that in itself needs to be integrated if its a non-linear spring (i've NO clue what ours are but I'm assuming it would be non-linear providing they're multi-leaf). Is the principle idea kinda the same? yes. Are the torsional forces acting enough? Most likely not. You're most likely seeing more effect from the compression forces than the torsional.

 

[ace_xp2]

As I mentioned before, that depends on initial spring rate, leaf width, bushing durometer, etc...
However, I will provide a few references here:
http://www.howeracing.com/p-7665-howe-full-leaf-springs.aspx
Here Howe makes reference to going with a lower than usual rate as necessary due to this effect.
http://forums.corner-carvers.com/showthread.php?t=10528
This is where I first read of this effect, and while it is admittedly hearsay, Bossbill has been around long enough that I would trust his reference of high durometer bushing= sway bar removal.

 

[jlangholzj]

As I mentioned before, that depends on initial spring rate, leaf width, bushing durometer, etc...
However, I will provide a few references here:
http://www.howeracing.com/p-7665-howe-full-leaf-springs.aspx
Here Howe makes reference to going with a lower than usual rate as necessary due to this effect.
http://forums.corner-carvers.com/showthread.php?t=10528
This is where I first read of this effect, and while it is admittedly hearsay, Bossbill has been around long enough that I would trust his reference of high durometer bushing= sway bar removal.

Oh I'm not denying the effect itself is there, I just don't think it would have a significantly noticeable effect as say adding a sway bar. Really the only way to know is to have a GOOD driver in the car with both scenarios.

Usually when we set a car up for racing, the corner weights and the initial settings are pretty universal...but after that its all drive time and adjusting from there. Its usually a solid week of drive time just in final set up to get everything ready for comp. No different in our cars

 

[ace_xp2]

Interesting, since the reference is that just bushing durometer increase roughly equalled the amount earned by a rear bar. Also, Howes statement should've provide a hint as to just how much of an effect it is...
As they said they must go with a lower rate than they would with coils, as otherwise roll stiffness would be too high. Not much point in adding bar when you've already got so much roll resistance you're cutting back on spring rate.

 

[65 fastback]

You won't find a rear sway bar on 99% of early Mustangs being driven on the track.

Tim

 

[jlangholzj]

I've seen plenty of early mustangs being driven with rear sway bars at all our local track events