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Rear sway bars, fact or myth?

Posted By: jcc

Rear sway bars, fact or myth? - 04/01/13 02:18 AM

New Improved- Does a rear sway bar ALWAYS improve the handling of a car?

OLD (Does EVERY car require a rear swaybar to handle better?)

YES or NO?

What say you? Define "handle" in your own way if needed.

I have an opinion.

Majority doesn't necessarily win

http://www.stealthtdi.com/SwayBars.html A reasonable middle of the road pun intended swaybar discussion
Posted By: amxautox

Re: Rear sway bars, fact or myth? - 04/01/13 02:24 AM

no

no
Posted By: amxautox

Re: Rear sway bars, fact or myth? - 04/01/13 02:25 AM

'handle properly'



'predictable'
Posted By: BigSugar

Re: Rear sway bars, fact or myth? - 04/01/13 02:30 AM

Quote:

New Improved- Does a rear sway bar ALWAYS improve the handling of a car?

OLD (Does EVERY car require a rear swaybar to handle better?)

YES or NO?

What say you? Define "handle" in your own way if needed.

I have an opinion.

Majority doesn't necessarily win




Why not just bolt one on and see for yourself ?

If you don't think it's an improvement you can always take it off.



Ron
Posted By: 5spdcuda

Re: Rear sway bars, fact or myth? - 04/01/13 02:44 AM

Personally I try not to use a rear bar on rear drive cars. An anti-roll bar always trys to lift the inside wheel. This can make trying to get the power down on corner exit pretty tricky especially if you have good power or marginal grip. As for defining "good handling" I see it as having good balance, sharp turn in and a good general feeling of confidence that it won't do anything weird.. Predictability is certainly desirable, but if the balance is really off it dosen't help your confidence just because you know ahead of time that the car is going to either try to suddenly swap ends or push itself off the outside of the corner.
Posted By: autoxcuda

Re: Rear sway bars, fact or myth? - 04/01/13 02:54 AM

Quote:

New Improved- Does a rear sway bar ALWAYS improve the handling of a car?

OLD (Does EVERY car require a rear swaybar to handle better?)

YES or NO?

What say you? Define "handle" in your own way if needed.

I have an opinion.

Majority doesn't necessarily win



No

No

Never absolutes on something like that. But they are an easy tool to make under/over-steer balance adjustments depending on the situation and driver preference.

It all depends on the rest of the handling system you are considering adding a rear sway bar to.
Posted By: runinonmt

Re: Rear sway bars, fact or myth? - 04/01/13 02:30 PM

I'm no suspension expert by any means but real world example: After noticing the improvement on my truck we bought a rear swaybar for my Stepson's '88 Ranger x cab. When he bought a new Ram QC in '03 the rear swaybar was the first improvement he made. He drives to Ft. Worth daily and he said the improvement on the onramps was impressive.
Ron
Posted By: Kern Dog

Re: Rear sway bars, fact or myth? - 04/01/13 08:21 PM

I know that my 70 Charger is more fun to drive with the current setup, which includes a rear bar.
I don't like understeer. I don't like excessive body roll either. The bar made huge reductions in both.
To those that run without one and are happy, are you also running extra firm leaf springs? If that is the case, it makes sense. The rear bar transfers spring rate from the outside wheel to the inside wheel in a turn. The use of a rear bar allows the driver to have a softer, more comfortable ride.
My car doesn't ride like an Imperial, but I like it. I'd rather have moderate spring/torsion bar rates and big sway bars for the street.
Posted By: RSNOMO

Re: Rear sway bars, fact or myth? - 04/01/13 08:33 PM

Quote:

I know that my 70 Charger is more fun to drive with the current setup, which includes a rear bar.
I don't like understeer. I don't like excessive body roll either. The bar made huge reductions in both.




Absolutely...

Got a rear sway on my '71 Satellite...

Big difference...
Posted By: Secret Chimp

Re: Rear sway bars, fact or myth? - 04/01/13 09:11 PM

Quote:

Personally I try not to use a rear bar on rear drive cars. An anti-roll bar always trys to lift the inside wheel. This can make trying to get the power down on corner exit pretty tricky especially if you have good power or marginal grip. As for defining "good handling" I see it as having good balance, sharp turn in and a good general feeling of confidence that it won't do anything weird.. Predictability is certainly desirable, but if the balance is really off it dosen't help your confidence just because you know ahead of time that the car is going to either try to suddenly swap ends or push itself off the outside of the corner.



Isn't omitting a rear bar on a RWD car really only of benefit on autocross where you have high grip + very tight turns? In any other situation I think you would want the roll stiffness.
Posted By: 72Swinger

Re: Rear sway bars, fact or myth? - 04/01/13 09:24 PM

Quote:

Quote:

Personally I try not to use a rear bar on rear drive cars. An anti-roll bar always trys to lift the inside wheel. This can make trying to get the power down on corner exit pretty tricky especially if you have good power or marginal grip. As for defining "good handling" I see it as having good balance, sharp turn in and a good general feeling of confidence that it won't do anything weird.. Predictability is certainly desirable, but if the balance is really off it dosen't help your confidence just because you know ahead of time that the car is going to either try to suddenly swap ends or push itself off the outside of the corner.



Isn't omitting a rear bar on a RWD car really only of benefit on autocross where you have high grip + very tight turns? In any other situation I think you would want the roll stiffness.

Usually in an Autox scenario a rear bar is a help. In theory in would make the car rotate in the tight turns of a tight turned course. I installed a rear bar on my Dart toward the end of last summer and it made a difference for sure. I can induce oversteer pretty easy with the throttle. And on long sweepers the car is definitely more confident and flat. One down side to it on my car is on turns where the pavement is broken up with cracks,seams or small potholes the rear is alot less compliant and wants kick sideways a little.
Posted By: Secret Chimp

Re: Rear sway bars, fact or myth? - 04/01/13 10:02 PM

Quote:

Quote:

Quote:

Personally I try not to use a rear bar on rear drive cars. An anti-roll bar always trys to lift the inside wheel. This can make trying to get the power down on corner exit pretty tricky especially if you have good power or marginal grip. As for defining "good handling" I see it as having good balance, sharp turn in and a good general feeling of confidence that it won't do anything weird.. Predictability is certainly desirable, but if the balance is really off it dosen't help your confidence just because you know ahead of time that the car is going to either try to suddenly swap ends or push itself off the outside of the corner.



Isn't omitting a rear bar on a RWD car really only of benefit on autocross where you have high grip + very tight turns? In any other situation I think you would want the roll stiffness.

Usually in an Autox scenario a rear bar is a help. In theory in would make the car rotate in the tight turns of a tight turned course. I installed a rear bar on my Dart toward the end of last summer and it made a difference for sure. I can induce oversteer pretty easy with the throttle. And on long sweepers the car is definitely more confident and flat. One down side to it on my car is on turns where the pavement is broken up with cracks,seams or small potholes the rear is alot less compliant and wants kick sideways a little.



I only know that the only situation where Miata owners omit the rear bar entirely is for autox because it helps keep the inside tire on the ground in extremely tight turns that transition to hard acceleration. Otherwise you want a rear bar to keep the car balanced at higher speeds. It is possible to have too much rear bar and get the wheel lifting at something more than a full-lock turn at 20 mph, but I don't think the answer is no rear bar at all.
Posted By: 5spdcuda

Re: Rear sway bars, fact or myth? - 04/01/13 11:38 PM

Your point is well taken. My response is simply that some cars like 'Cuda's are a little "tail happy" to start with and adding a bar can actually make the situation worse. If I were inclined to compete more seriously I would like to try some fiberglass springs with a lower spring rate with a light and adjustable rear bar. I think it might be a useful way to tune for different courses and road conditions. To digress for a moment, I've learned from experience that basic theory is almost always a good starting point, but you only find out what works by actually trying it. Driving style and preference certainly enters into it as well. The following is a good example of how theory and actual results can differ. Theory says that using stiffer springs or anti-roll bars at the front tends to increase understeer. This would probably be true except for the fact that most cars [ especially older ones with stock suspensions like were talking about here ] have so much body lean in hard cornering that they generate considerable positive camber even if you start out with some static negative camber. The use of stiffer springs and/or bars reduces the body lean to more manageable proportions and as a result understeer is often reduced and the car "turns in" better. As a side note live axles or beam axles don't experience much if any camber change with body roll unless it's so great as to actually lift the inside wheel clear of the pavement. One final note, Eberg's "Green Brick" was an "A" body with a relatively light weight small block and probably somewhat better weight distribution than most "E" bodies and he still choose to run without a rear bar.
Posted By: autoxcuda

Re: Rear sway bars, fact or myth? - 04/02/13 01:36 AM

Quote:

Quote:

Quote:

Quote:

Personally I try not to use a rear bar on rear drive cars. An anti-roll bar always trys to lift the inside wheel. This can make trying to get the power down on corner exit pretty tricky especially if you have good power or marginal grip. As for defining "good handling" I see it as having good balance, sharp turn in and a good general feeling of confidence that it won't do anything weird.. Predictability is certainly desirable, but if the balance is really off it dosen't help your confidence just because you know ahead of time that the car is going to either try to suddenly swap ends or push itself off the outside of the corner.



Isn't omitting a rear bar on a RWD car really only of benefit on autocross where you have high grip + very tight turns? In any other situation I think you would want the roll stiffness.

Usually in an Autox scenario a rear bar is a help. In theory in would make the car rotate in the tight turns of a tight turned course. I installed a rear bar on my Dart toward the end of last summer and it made a difference for sure. I can induce oversteer pretty easy with the throttle. And on long sweepers the car is definitely more confident and flat. One down side to it on my car is on turns where the pavement is broken up with cracks,seams or small potholes the rear is alot less compliant and wants kick sideways a little.



I only know that the only situation where Miata owners omit the rear bar entirely is for autox because it helps keep the inside tire on the ground in extremely tight turns that transition to hard acceleration. Otherwise you want a rear bar to keep the car balanced at higher speeds. It is possible to have too much rear bar and get the wheel lifting at something more than a full-lock turn at 20 mph, but I don't think the answer is no rear bar at all.



Are those Miata's in stock classes that have to run stock springs and stock width tires?

It all depends on the individual car and it's spring/shock/swaybar/tire setup. All results will very.
Posted By: jcc

Re: Rear sway bars, fact or myth? - 04/02/13 01:41 AM

My thinking has been, if adding a rear bar helps a lot, you likely don't have the proper front bar/spring combination in the first place. Of course I am sure there are chassis' not stiff enough to transmit roll resistance and a rear bar bypasses that shortcoming, but that's a different topic.
Posted By: Secret Chimp

Re: Rear sway bars, fact or myth? - 04/02/13 01:51 AM

Specific setups aside, I can't bear to see people arguing that rear bars should not be necessary as a general rule. Come on, guys. Our cars may be 40-50 years old but the general suspension theory we're working doesn't have to be...
Posted By: Supercuda

Re: Rear sway bars, fact or myth? - 04/02/13 02:54 AM

It really depends.

Best handling car I ever built was vastly improved with a rear bar. But unless you have major buxs you can't always get the exact setup you need, so you tune with what you can get.

If you like stiff springs, then you can get away with no, or a small, rear bar.

If you like to keep your dental work where it belongs you are probably running a rear bar.
Posted By: Kern Dog

Re: Rear sway bars, fact or myth? - 04/02/13 04:05 AM

I mounted a rear bar on my 2007 Ram 1500. I got one from a mid 90s Chevy Suburban and modified the mounts.
The truck certainly corners flatter than before. The 305-40-22 tires I run are wearing more even in the front now. prior to the install, the outer edges would get scuffed from aggresive driving. It seems that now with the truck having less body roll, the front tires are not rolling over as much.
I don't notice that much of a difference in turn in or in tight switchbacks, but in steady freeway on ramp type activity.
Posted By: autoxcuda

Re: Rear sway bars, fact or myth? - 04/02/13 04:11 AM

Quote:

My thinking has been, if adding a rear bar helps a lot, you likely don't have the proper front bar/spring combination in the first place. Of course I am sure there are chassis' not stiff enough to transmit roll resistance and a rear bar bypasses that shortcoming, but that's a different topic.



I think there is some truth to that. But do you carry sets and sets front and rear springs in 50 lbs increments out to the racetrack? And those springs should be rated with a Longacre type checker before install too. Advertised rates are rarely correct. Especially with leaf springs.

And it depends what track you are running at. And depends on your driving style and skill level.

I know at the tighter and slower Horse Thief Mile track at Willow Springs I liked running my rear sway bar.

But at the wider turned and faster Big Track at Willow Springs I like the rear sway bar disconnected. It got me in trouble the first time out with a decent motor. After that incident, I just disconnect one end link with two 3/4" wrenches. I should have taken the link totally off, but this time I just unhooked the end Oh well: http://www.youtube.com/watch?v=TLOrFexa6Fk
Posted By: patrick

Re: Rear sway bars, fact or myth? - 04/02/13 01:40 PM

Quote:

Quote:

Personally I try not to use a rear bar on rear drive cars. An anti-roll bar always trys to lift the inside wheel. This can make trying to get the power down on corner exit pretty tricky especially if you have good power or marginal grip. As for defining "good handling" I see it as having good balance, sharp turn in and a good general feeling of confidence that it won't do anything weird.. Predictability is certainly desirable, but if the balance is really off it dosen't help your confidence just because you know ahead of time that the car is going to either try to suddenly swap ends or push itself off the outside of the corner.



Isn't omitting a rear bar on a RWD car really only of benefit on autocross where you have high grip + very tight turns? In any other situation I think you would want the roll stiffness.



generally adding roll stiffness to the front promotes understeer, adding roll stiffness to the rear promotes oversteer. on my old M body, when I upgraded the front to the cop spec 1.125" bar, and hadn't put on the rear bar, the thing pushed like a plow, it just wouldn't turn. I actually went to a 1" rear bar, and it made it very responsive, possibly almost slightly biased towards oversteer. also, wider tires on the back relative to the front helps induce understeer, so you may need more rear bar if you run a staggered tire setup.

the big difference between miatas and mopars is the miata is IRS, while the mopar is a live axle. adding roll bars on an independent suspension makes them a little less independent, so how a miata reacts to a rear sway bar is somewhat different than how a live axle vehicle will...
Posted By: TC@HP2

Re: Rear sway bars, fact or myth? - 04/02/13 06:25 PM

In the simpilist terms, its the roll couple distribution.

Based on the front/rear weight bias, a car is going to want a specific roll couple percentage to produce equal force at all the tires.

Outside of that, the roll couple is simply the front springs and swaybars as a percentage of the rear springs, and if so equiped, rear sway bars.

You can achieve these same percentages without a sway bar, but, the use of a bar typically allows the use of lower spring rates to produce the same amount of roll resistance.

As noted, different cars on different courses with differing requirements will react in different ways to the addition or subtraction of rear sway bars. In classes I have run competitively, rear sway bars were never allowed, even if they did come that way from the factory. We just used the necessary spring rates to achieve the percentages required.

So the original post, no and no.
Posted By: feets

Re: Rear sway bars, fact or myth? - 04/02/13 10:35 PM

Just to throw a wrench in the works...

I have moderate springs (front and rear) in the hot rod. The front wears a 7/8" factory bar and the rear has a 3/4" bar. This is no hard core corner carver but it does run 245/45-18 and 295/45-18 Nittos for a little grip.

The car was nicely balanced. Sure, there's some body roll but nothing extreme.

I haven't driven it much since I put it back together. I know there has been some considerable weight loss up front. Removing the turbos, manifolds, wastegates, associated plumbing, and the large intake manifold made the front end sit noticeably higher. A little weight was offset by replacing the Eddy heads with irons but that didn't bring the front end back down.
Less nose weight should reduce the push a bit. I'll have to fiddle with it a bit more and see how it handles now.
Posted By: ek3

Re: Rear sway bars, fact or myth? - 04/02/13 11:47 PM

Quote:

In the simpilist terms, its the roll couple distribution.

Based on the front/rear weight bias, a car is going to want a specific roll couple percentage to produce equal force at all the tires.

Outside of that, the roll couple is simply the front springs and swaybars as a percentage of the rear springs, and if so equiped, rear sway bars.

You can achieve these same percentages without a sway bar, but, the use of a bar typically allows the use of lower spring rates to produce the same amount of roll resistance.

As noted, different cars on different courses with differing requirements will react in different ways to the addition or subtraction of rear sway bars. In classes I have run competitively, rear sway bars were never allowed, even if they did come that way from the factory. We just used the necessary spring rates to achieve the percentages required.

So the original post, no and no.

This totally sums it up....this is not only an opinoin , it is also the facts !
Posted By: Mopar Mitch

Re: Rear sway bars, fact or myth? - 04/03/13 04:32 PM

I've experimented with different size sway bars.. frint and rear,, as well as the bushings (combos between rubber and urethance).. and the shock settings (adjustable Konis).. and different torsion bar rates, and a few different rear leafs, and different ride heights.. and having the car properly balanced side-to-side, and trying to remove weight (where ever legal, per class rules of the SCCA Solo E/SP). Depending what you want to do with the car, a rear bar can be a major improvement, but all together, it has to be a "package" that will make the biggest difference for the driving you intend. I currently have 1.25 solid front bar, and 1.0" solid rear bar. But... i've played with the shock settings, and made my final decisions on how and where i drive the car. On a pylon autocross course... its great! On a hi-speed road course.. just a little chance of over-steer, but then I haven't pushed it hard enough to get oversteer.. could change the rear bar to the stock 0.75" bar, or simply soften the rear schocks. I'm very staisfied with the current setup of sway bars.. would change to a hollow front bar for weight savings (this wasn't available many years ago when I originally had my solid bar made), and change to an adjustable rear bar... things i may eventually do.

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