Sorry I'm pretty much useless at anything mechanical, and this is going to be a stupid n00b question. I've read through some posts and it seems to be the general consensus that adding a rear swaybar to a pre-88 will significantly improve handling.

What I'm wondering is what symptoms( or issues) will it fix and does it have any adverse effects?

The swaybar will increase the spring rate of the inside spring and decrease the rate of the outside spring. Adding a rear swaybar will actually make the rear lose traction. If you're not careful, you can get into trouble in the rain, snow, or just going too fast around a turn (say hello curb, or another car). It's deceiving because your car will corner flat and feel like it has more traction too.

In short: your car will not push (understeer) through a turn, it will be closer to balanced.

Thanks for the info! It sounds like the overall effects of adding the swaybar are more negative than positive.

Is this loss of traction outweighed by the decrease in understeer? I'm guessing the answer is probably that it depends on the application, right? If so would it be beneficial in everyday around town driving or in autocross?

The results are more positive than negative.

A Fiero without a rear bar is prone to understeer. Most factory cars are setup this way because it's safer.

A rear bar can balance the car. When it's first installed, the car will feel totally different.

It is most benificial on a V6 Automatic Fast Back car. But any automatic car will see a benfit from it. It will reduce understeer (front end push) by keeping the car more flat in turns, but when you are at your limit of a corner, it can cause the back of the car to slide out on you. Can be very scary the first few times it happens. But also can be fun once you get use to it. I personally love driving in the rain and sliding the car around. If you try to do that in the dry with a stock fiero the front will push way before the back is gonna slide I personally would rather have the drive wheels slide than teh steering wheels anyway. But that is just me. (sorry about the spelling tonight)

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David hotrodfiero@shaw.ca
85GT 2.9 4spd

Here's one for you...

I have seen post daying the '86 had a 7/8" bar in front and no rear bar. Which I think is correct. Most posts on this subject insist you put that front bar on the rear and put a larger 1" bar up front. I won't say who, but one post insists on a 7/8" or 1" up front and one a full 1/4" larger in the rear. "You want to stiffen up the rear..."

What's the optimum for a pre '88 that you want to handle like a steel roller coaster...stick to the road with CONTROL!?

TIA

Brent

[This message has been edited by rabid-wombat (edited 08-17-2002).]

Any recommendations on installing a rear sway bar on a 1988 coupe? I have a front sway bar from a 1984 Fiero that I would like to use. I'm open to suggestions about mounting this critter.

Is it better to have a bigger sway bar on the front or rear? Or should they be the same size?

When I was asking about suspension upgrades, people told me it was better to have the rear bar be smaller than the front.

Ed

It is most benificial on a V6 Automatic Fast Back car. But any automatic car will see a benfit from it. It will reduce understeer (front end push) by keeping the car more flat in turns, but when you are at your limit of a corner, it can cause the back of the car to slide out on you. Can be very scary the first few times it happens. But also can be fun once you get use to it. I personally love driving in the rain and sliding the car around. If you try to do that in the dry with a stock fiero the front will push way before the back is gonna slide I personally would rather have the drive wheels slide than teh steering wheels anyway. But that is just me. (sorry about the spelling tonight)

Why would it be best on the automatic. Reading the torque steer thread, they feel that the automatics handle a little better.

Trev

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"You obviously have a great economy with words, I look forward to your next syllable with great eagerness"

having a smaller rear sway bar on a front mounted rwd would make more sense to me. but on a midengine, a larger or same size rear sway bar would help even more b/c the weight is mainly in the back particularly on the passenger side does this make any sense to ya'll? I think thats the configuration i will go with... looking at performance videos of mid engine vehicles show that there are always more sway in the rear than the front. also I would think that the front is where you would want a little more sway than the rear. wow you guys got me thinking now.. what you are trying to do is balance out the car when turning, especialy at high rates of speed. I will tell ya that my car without the rear sway bar will kick out the right back end even on dry pavement and I have a stock 2.5l. but I will eventually put a larger engine in (as soon as the economy moves in my favor). I will definatly have to beef up the suspension then.

[This message has been edited by atarian (edited 08-17-2002).]

I think you need the bigger bar on which ever end of the car that has more weight to control.
Front engine cars need a bigger bar in the front.
Fieros need a slightly larger bar in the rear.
Most suspension theory assumes the engine is in the front, with the fiero this is not the case.
But that is just my opinion.

tstroud

this came up awhile ago. The whole reason for the larger front bar in a fiero is so you maintain some of the safer driving characteristics found in the car. People who drive competitivly find equal bars more useful

Trev

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"You obviously have a great economy with words, I look forward to your next syllable with great eagerness"

The 88 cars came with the rear anti-sway bar stock. If you put polyurethane bushings on the front anti-sway bar and end links you will balance out the cars handling even more and make the back end less likely to swing out on you in a hard corner.

The benefits of the rear anti-sway bar from a performance stand point out weigh the negatives. The car will feel more stable and planted in everyday driving. It’s only at the cornering limits that the rear end of the car can swing out on you and it only usually happens if you brake or let off the gas while in that hard corner with the fiero. Going with a larger tire in the back will also give you more rear traction too making the likelihood of the rear swinging out even less on dry pavement. When things get slippery though that all changes!

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'88 coupes did not have rear bars from the factory. '88 Formulas and GT's did.

The theory behind how to size front and rear anti-sway bars is a good bit more complicated than "big front, small rear". Whenever this tpic comes up somebody always pipes up and says "You always want a bigger bar on the front than the rear". Rubbish!

To give the car balanced handling, first it needs balanced traction. This is accomplished by matching tire width to weight distribution: 45/55 F/R weight distribution matches with a 45/55 F/R rubber distribution. 205-215 front and 255 rear tires do this well. This give each end of the car the same grip per pound of weight.

In order to use the tires optimally, the roll stiffness of each end of the car must be matched to the roll moment, so that the same lateral G yields the same degree of body roll at each end. This can get comlicated as suspension geometry relative to roll center location and CG height determine roll moment, and the calculations to determine roll stiffness involve motion ratios for both springs and anti-roll bars, as well as lever length of anti-roll bars.

Anyway, install it and see if you like it. If you don't like it, change it.

quote Originally posted by Will: '88 coupes did not have rear bars from the factory. '88 Formulas and GT's did. The theory behind how to size front and rear anti-sway bars .......Anyway, install it and see if you like it. If you don't like it, change it.

Will, I should have asked you to add input on a previous thread... Thanks for this, it is good info ...PC

IF you drive at 8/10s or less you don't need a rear bar at all!!!!
only if you want to driver near the 10/10 limit do you want the rears to breakaway first so you can then control a drift!!!!
this an't safe and sane on the streets!!!
but on a deserted road IT IS FUN!!!!
if at the limit fronts breakaway first YOUR LOST!!!!if the rears do it first you still can control the car!! thats why you want a bigger front bar and a front sized rear so the front just balances rears new bar with a slite rear breakaway bias so it will drift eazy in a controled mannor.
auto-X only like equal bars or bigger rears to keep looser than fronts by a lot for lots of overstrearing on tight cone tracks
but most will not like a street setup like that

GPL sim is a good way to learn about balance in effects of changing F/R bar stiffness
here is a free demo down load of it at watkins glen track http://www.papy.com/gpl/gpl.download.index.html
scroll down to the demo
also get the 1.2 update patch and the speed fix and patch for your vidio cards type
once you can keep the car on the track go to the pits and play with the bars

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Question wonder and be wierd

[This message has been edited by ray b (edited 08-17-2002).]

Here's a brief explanation of how suspension setup affects handling.

When you go into the corner the car will transfer weight to the tires on the outside. This means that more of the car's weight is supported by the outside tires than the inside. Since the outside tires have a lot of weight and the inside tires don't have as much your traction isn't as good as it would be if both tires had the same amount of weight on them.

Spring rates affect the amount of weight transfer. Softer springs transfer less weight to the outside tires. Stiffer springs transfer more weigh to the outside tires.

Now let's talk about understeer and oversteer. Understeer is when the front has less traction than the rear of the car. It slides and the rear sticks. Oversteer is the opposite -- the front has more traction so it sticks and the rear slides. Ideally, we want both ends to have the same amount of grip so they'll both stick equally. If we push it to hard into a corner, we ideally want the car to slide perfectly sideways. We don't want to go straight (understeer) and we don't want the back end coming around (oversteer).

How do we change the understeer / oversteer characteristics of the car? By giving one end more traction than the other. How do we do that? We change spring rates. Let's say you have really stiff front springs and really soft rear springs. When you go into the corner the front is going to transfer lots of weight to the outside and therefore have less grip. The rear isn't going to transfer as much weight to the outside so it's going to have more grip. You now have understeer.

What do sway bars do? They actually do the exact opposite of what SCCA Fiero said it does. When the car rolls to the outside of a corner, the sway bar increases the spring rate of the outside spring and decreases the spring rate of the inside spring. This transfers more weight to the outside tire so you have less grip at that end of the car. The bigger diameter the sway bar is, the stiffer it is, and the more weight is transfered to the outside.

In the case of the '84 - '87 Fiero, this is how it comes from the factory. The front sway bar adds spring rate to the outside front in a corner, giving the front less traction. If we add a sway bar to the rear, we will transfer more weight to outside rear in a corner. This gives the rear less traction so we add oversteer or decrease understeer. Since the front and rear are better balanced it's a net gain in cornering grip. We could get the exact same affect by increasing the rear spring rate instead of adding a rear sway bar. This is important to remember. Sway bars exist because they allow you to have the suspension soft enough to be comfortable soaking up bumps, but they add spring rate in the corners to reduce body roll.

Everything making sense so far? If it is, you should be able to see that such blanket statements like "the front sway bar should always be bigger" or "the rear sway bar should be bigger because that's where the weight is" are complete nonsense. The sway bar and the spring rates are interrelated so it's impossible to talk meaningfully about one without knowing the other. With the right selection of springs and bars you could set up a Fiero to handle well with a front sway bar only, a rear sway bar only, a front and rear sway bar, or no sway bars.

With all that said, what size sway bar should you add? I've heard that if you bolt a stock front bar on to the rear of the car you get a little too much oversteer, so you'd want to increase the size of the front bar at the same time to balance things out. Yes, oversteer is fun and it makes you feel like you're driving hard and going fast, but a neutral handling car is going to be faster through a corner.

I said at the beginning that this is a brief explanation and as long as this is, believe me, it's brief. There are entire books written about this stuff. Two good ones are Fred Puhn's How To Make Your Car Handle and Carol Smith's Tune To Win. Suspension tuning is complex I have left out a ton of stuff like body roll, roll centers, mass centers, camber curves, shocks, etc. I wrote some shock stuff in this thread the other day if you're interested in that.

I hope this helps.

Oh, mindscape: The best bet for you is to find a stock rear bar and brackets from an '88 GT or Formula. It'll bolt right on. The spring rates on many '88 coupes are identical to the GT and Formula. One others the front is just slightly softer. A stock bar from a GT or Formula will be perfect for you.

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Doug Chase
Duvall, WA
'88 Fiero Formula 5-spd (autocrosser)
'88 Fiero GT 5-spd (daily driver)
'85 Fiero GT 4-spd (rally car)

quote Originally posted by SCCA FIERO: The swaybar will increase the spring rate of the inside spring and decrease the rate of the outside spring.

I just got the words in the wrong order.

Any chance you could provide us with a size or maybe even part number for a rear sway bar then? Or would I really be better just looking thru junkyards until I find one on an 88?
Just curious! Thanks!

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87 GT V6 Fiero Automatic

quote Originally posted by Banner: Any chance you could provide us with a size or maybe even part number for a rear sway bar then? Or would I really be better just looking thru junkyards until I find one on an 88? Just curious! Thanks!

if you only have a 87 why do you want a 88 part???
it will not fit or work right on a earlyer car!!!
for your 87 you move the front bar to the back and get a bigger aftermarket bar for the front

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Question wonder and be wierd

Simple. I don't want to take the front bar off and move it to the back, and put on a new front bar. I just want to put a bar on the back myself.

Doug seemed to indicate that you could take the rear bar off of an 88 and put it on the 87. I might have been mistaken on that though.

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87 GT V6 Fiero Automatic

[This message has been edited by Banner (edited 08-17-2002).]

quote Originally posted by Doug Chase: ........In the case of the '84 - '87 Fiero, this is how it comes from the factory. The front sway bar adds spring rate to the outside front in a corner, giving the front less traction. If we add a sway bar to the rear, we will transfer more weight to outside rear in a corner. This gives the rear less traction so we add oversteer or decrease understeer. Since the front and rear are better balanced it's a net gain in cornering grip. We could get the [b]exact same affect by increasing the rear spring rate instead of adding a rear sway bar. This is important to remember.... [/B]

So... if I understand this right...Adding weight to the rear of a fiero means that I need wider than stock tires in the rear to keep the ratio of front to back tire support weight the same as stock.. An then I need to add heavier springs (coil-overs)to the rear to support the extra weight added to the rear...( and that would also keep the unequal length axles from moving up and down as much under hard acceleration).. and adding(replacing the stock one) a thicker (stiffer) bar in front to counter the effect of the heavier springs that were added to the rear.. which would then bring everything back... well, close to.. the stock (front understeering) car ..Then I could begin the fine tuning to achieve the precise handling that I wanted by replacing the heavier front bar with a lighter ( stock ) one, or adding a small bar to the rear (which would stiffen up the rear even more) to promote a more neutral handling car... ???
TIA...PC

Doug and I have both left out a couple of things thus far.

Tire traction is not linear. A tire with 100 lbs of load on it may be able to absorb 110 lbs of lateral force without sliding, while the same tire with 400 lbs of load on it may only take 350 lbs of lateral force to slide. The more weight on a tire, the less lateral force, proportionally, it can absorb. If you think about it a little, you realize that you can relate a tire's holding force to contact patch pressure rather than total load. Contact patch pressure is also caled ground pressure. This gives you a tool to use in suspension setup. Sizing tires to be proportional to weight distribution is really just equalizing ground pressure between the front and rear. A Fiero with the same size tires all around will have higher ground pressure in the rear than in the front, giving the rear less holding power, relative to the weight with which it's loaded. This is why F1 cars are so touchy: the tire sizes which they are allowed to run don't give them enough rubber in the rear to properly deal with their rear weight bias. This makes the window of good suspension setups very narrow and makes the car hard to dial in.

A Fiero with the right size tires, but the wrong suspension setup will obviously still have bad manners. For example, in a car with extreme roll stiffness in rear, but almost nothing in the front will oversteer. However, what hasn't been mentioned is the interaction between front and rear suspensions. On a car with no front roll stiffness, the roll moment will try to roll the chassis to the outside. Assuming sufficient chassis stiffness, the roll of the front end of the car will be trasnferred by the chassis to the rear suspension and resisted by the rear roll stiffness. This grossly overloads the outside rear tire, giving it less traction proportional the force with which it's loaded and causing it to slide--oversteer.

This leads to my philosophy of good suspension setup: match the tires to the load they have to carry, then match the f/r roll stiffnesses to the f/r roll moments to that each end of the car will roll the same amount with the same lateral acceleration, preventing the transfer of load from one end of the car to the other, keeping each tire loaded as optimally as I can. That's really the crux of suspension tuning: just make sure nothing in the suspension gets in the way of the tires doing their job.

The above mentioned F1 car will be set up with a good bit of front roll stiffness to transfer load from the outside rear to the outside front. At low speeds anyway; at high speeds the chassis tuning is impacted far more by aerodynamic downforce and its balance front/rear.

Excellent explanation Doug.

quote Originally posted by Will: [B........A Fiero with the right size tires, but the wrong suspension setup ... [/B]

Got it.. Thank you Will and Doug I am really glad that you take the time to explain things. This is the part that I was missing in creating my vision of what I wanted from my Fiero. Keep up the good work ...Thanks again.. PC

quote Originally posted by SCCA FIERO: I just got the words in the wrong order.

That's what I thought. I figured that somebody with the username SCCA Fiero probably knew how sway bars work.

Banner, I told mindscape to dig up an '88 rear bar because he has an '88 coupe and it'll bolt right on. An '88 rear bar won't work on an '84 - '87 because it needs to mount where the tie rods attach to the frame.

One thing that I left out above is that the stiffness of a sway bar is dependent on three things -- bar diameter, bar length, and arm length. If you have a 1" bar with a 1 foot lever arm it's going to provide a lot more resistance to twisting than a 1" bar with a 2 foot lever arm. Similarly, it's going to be easier to twist a 1" bar 10 degrees if it's 10 feet long than if it's 4 feet long. How to Make your Car Handle has the formula for calculating sway bar stiffness.

When you attach a sway bar to the car you have another variable that affects the effective stiffness of the bar -- where the bar attaches to the suspension. On an '88 the rear bar attaches directly to the strut. On an '84 - '87 the rear bar is typically mounted to the center of the control arm. This gives the wheel more mechanical advantage on the bar so the bar is effectively softer.

For these reasons it doesn't necessarily make sense to compare just the rear bar diameter on an '88 vs. a pre-'88 because there are a lot of variables that aren't accounted for.

Suspension setup is tricky and no matter how much math you do beforehand it still involves a lot of trial and error to get things right. On my rally car I'm on the second set of springs and my second try at shock valving. I'm sure I can get better from this but right now it's good enough that my driving is definitely the weakest link.

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Doug Chase
Duvall, WA
'88 Fiero Formula 5-spd (autocrosser)
'88 Fiero GT 5-spd (daily driver)
'85 Fiero GT 4-spd (rally car)

[Edited for clarity]

[This message has been edited by Doug Chase (edited 08-18-2002).]

quote Originally posted by Doug Chase: On an '84 - '87 the rear bar is typically mounted to the center of the control arm.

Typically.... just not on my car.

I mounted the bar a couple of inches further back from the usual position. I used '88 end link brackets on the back of the struts and ran ~11" long rod-end links. The setup is very nice, but has perhaps a taste too much oversteer. I'm thinking of using a modified #588 Addco bar (XJ6 Jaguar) on the front to give me some room to put a REALLY big battery under the spare tire.
https://www.fiero.nl/forum/Archives/Archive-000001/HTML/20020511-2-010981.html

Doug Chase has the correct facts and explanation of the effects of sway bars on the Fiero, or any other car for that matter.

I would like to re-emphasize one of his points, however , and add another one that was not mentioned by anyone yet.

When you add a anti sway bar, or increase the size of one, you are DECREASING the traction on that end of the car for cornering. If that brings the car into "balance" for steady speed cornering, as on a skid pad, it "COULD" be an improvement. However, I have ALWAYS found that you can improve the cornering traction of American made cars enough to get balanced steady speed cornering with no rear sway bar, just by improving the camber, caster, and toe of the front suspension, and adding solid pillow blocks and endlinks to the front sway bar. This IMPROVES the front suspension instead of lessening rear cornering traction, which increases the total "G" force the car can develop cornering, with neutral handling at a highter level.

Always remember that the STIFFER you make the suspension at one wheel, the POORER the traction will be at that wheel, for cornering, braking, AND accelerating.

Obvioously, a certain amount of stiffness is neccesary to avoid the car from turning "turtle", but there are usually better ways to get a car neutral then just to add bigger sway bars and stiffer springs.

Fieros already come with a tendancy to oversteer at the limit of traction from the rear getting too loose, and adding more sway bar on the back WILL MAKE THAT WORSE.

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Gerald Storvik

http://www.8shark.com/

how does making the sway bar links affect the stiffness of the bar? or does it make much difference as long as it tight?

very interesting thread.

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Two 88FORMULAS Red & Yellow
SSFiero@Aol.com

Hmm. perhaps I f I put larger (wider/taller) wheels/tires on the rear I will need a small swaybar on the rear? Especially if I go larger on the front? Todays' performance tires are better at grip than those of 15 years ago, and the 7/8 inch swaybar was for 'average' drivers.

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John DuRette
85 SE

putting solid pillow blocks on the front sway bar and putting solid endlinks on the front bar, (heim joints or ball joints) increases the bar effective bar stiffness about the same as 1/16" larger bar diameter would.

The actual bar stiffness is not increased at all, you are just getting rid of all the mushy slop of the rubber or poly doughnuts, so weight transfer is instant instead of the car having to lean over a few degrees before the slop is taken up. This results in less body lean by a few degrees before the bar is fully loaded. Since the actual bar rate is not changed, there is no loss in front traction as a larger bar would do, and rear traction is increased at the same time. This is one of the few mods that actually has no negative effect. The instant weight transfer with this mod results in a car that is noticeably quicker to respond to steering inputs, has slightly less body lean, and better rear traction for accelerating, braking, and steady speed cornering.

This mod, along with added caster and negative camber, can result in a Fiero that has virtually no tendancy to "push" or understeer, with more neutral handling right up to the limit of adhesion, and less severe looseness in the rear at that limit. I would theororize that wider rims/tires on the rear would further reduce or eliminate the oversteer at the limit of adhesion.

My advice would be to only use a small rear bar and larger front bar if the car is going to be equipped with actual racing tires (for road racing or autocrossing) that have significantly more grip than regular street tires. The increase in cornering power of this type of tire results in more body roll, and then larger bars become neccesary.

Any Fiero with this type of setup will achieve higher numbers on a skid pad than with bigger bars and/or stiffer springs.

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Gerald Storvik

http://www.8shark.com/