krismarsel1

My buddy has a 305 91 RS, and I have a 89 173 RS. He donated his stock sway bar to my car and I noticed it doesn’t drive as nice as it did. Were they different sizes? If so.. would it be worth keeping it and balancing it out with a new sway bar in the rear, or go back to stock.

Thanks

John in RI

iTrader: (167)

Install the thickest / biggest ones you can find,..... front and rear.

86firebird350

Were they different sizes? Most likely. V6 cars got the smallest of pretty much everything the factory offered (spring rates, exhaust size, sway bars, etc.) You can physically measure their OD to find out if they are different. I think the front sway bars ranged in size from 30 to 36mm, with some being solid and others being hollow. I'm not 100% sure on the size range so don't quote me on that.

Bigger is not always better with sway bars. In general, sway bars should be used as a "tuning" device AFTER you've setup your suspension and chassis (spring rates, shock valving, alignment, etc.). The link below is a good read on what sway bars are and how they work. Don't just throw the biggest one in that you can find like John suggested (hopefully he was being sarcastic).

http://www.stealthtdi.com/SwayBars.html

//<86TA>\\

iTrader: (14)

Yeah but honestly on a 3rd gen,.bigger is better up front 99.9% of the time. The rear is a different story

John in RI

iTrader: (167)

I was not being sarcastic,....... At all.

As long as the car still has the factory installed springs - install the LARGEST front and the LARGEST rear sway bar you can if you want to improve the cars handling.

** Using POLY bushings will also effectively increase the size of the bar a MM or 2. Example: POLY bushing with 23MM bar is about = to a rubber bushing & 24 MM bar.

If you replace the Springs with something aftermarket and have the knowledge and ability to PROPERLY adjust the car on the track - then worry about matching springs and sway bars. If your an every-day "Joe" than wants a better handling Thirdgen in under an hours time....... install the biggest bars you can get.

Largest factory Thirdgen bars =
34mm solid front
36mm hollow front
25mm solid rear

//<86TA>\\

iTrader: (14)

34 front is hollow.

John in RI

iTrader: (167)

Check the factory Sway Bar dimensions on the 85 Trans Am,.......

86firebird350

Note that the OP has the little 2.8 V6 powerplant, not a heavy V8. You definitely don't want a big heavy front sway bar on a V6 as there just isn't enough weight to induce enough lateral roll to warrant a big sway bar. Too big of a front sway bar in a V6 and the car won't be able to transfer the weight side to side and will reduce grip (as well as ride quality).

As a whole, I've found that bigger rear bars in cars like ours that don't have a lot of weight in the back is not a good combination (although V6 cars are a bit different and not my area of expertise). The stock 24mm sway bar on my GTA made the car VERY tail happy and overall it wasn't as stable in the corners as I'd like. This was with Koni shocks/struts, Eibach springs, solid strut mounts, poly bushings and end links, and new 245 tires. On the other hand, my base model Firebird with the L03 wasn't nearly as tail happy in the corners with it's 32/18 setup, and that car was stock suspension on much narrower 215 tires.

stealtht/a

iTrader: (1)

Weren’t the v6 cars equipped with front bars only ?
If so adding a rear bar would prob balance things out

TEDSgrad

iTrader: (4)

Provided we're talking V8. So you only need one front bar.
Rear you need to experiment (2 or more bars). Not every car is the same, nor is every preferred driving style the same.

//<86TA>\\

iTrader: (14)

I used a 36 front with 750lb springs on my 3.1 car and it was phenominal

John in RI

iTrader: (167)

That's my starting point..... way back in 92 with a factory stock (V8) 84 Berlinetta with no factory rear sway. Since then I've installed every sized bar made - while using factory springs - under a few dozen of these cars I've been threw.

Just a fact worth noting. Increasing the size of the front bar from a stock 32 to a "HP" 34 or 36 will increase understeer ( plow ) but when increasing both bars at the same time the this increased size to the front is more to "keep up" with the ( more important ) larger rear bar.

Edit--->
Since stock fronts only got as large as 36 and the rears as large as 25,...... I feel VERY CONFIDENT that there is never going to be a factory bar that is too big. Past experience has provided me with all the "proof" I'll ever need.


Quoted sections taken from "The Camaro and Firebird Performance handbook".

He installed a 91RS front bar,........ how big could that be ?? 32mm ?? ( I'm surprised the V6 Firebird bar wasn't bigger than the RS bar. ) He's gotta' get the largest rear sway bar that he can - period. ( same is true for every other Thirdgen owner. ) There's no way you can compare the way your 24 mm bar felt on a completely aftermarket suspension and POLY bushings/end links to the way an 89 Firebird is going to feel once it gets a larger bar in the *** end.

The only time I've ever had to reduce the size of my rear sway was after installing a 24mm IROC rear bar under my 95Z. ( BIG mistake ! )

86firebird350

John, I don't disagree with any of the materials that you've referenced. In fact, that's all very good info. I just think that you're trying to apply sound logic for setting up the suspension of a V8 3rd gen to a V6 3rd gen, which you can't do. The V6 car's smaller, lighter powertrain has a Cg lower to the ground and further back, requires a softer front spring, and has better weight bias front to back as a result. All of which has an effect on the sway bar combo that works best in those cars.

My point of contention with your post that I wanted to clarify was the generalization of "bigger is better" for sway bars (front AND rear) which is not the way to go about it. As I've pointed out before, sway bars should be used as a fine tuning aid for the suspension after the larger pieces of the suspension puzzle have been figured out. I don't doubt that the OP may need bigger sway bars, but to say he should put on the biggest sway bars available is wrong. I'll go back to my GTA as an example. Bone stock, the car pushed bad in the twisties but that wasn't because my sway bars weren't "big enough" to correct the understeer condition. It was because the stock bushings, shocks/struts, mounts, etc. were garbage from age and use and allowed more body roll than any sway bar could effectively mitigate. Once those areas were addressed, I found that the car would actually oversteer with that sway bar setup and would have needed a smaller bar in the rear to correct the problem.


I DON'T think that a V8 RS front sway bar is too big for a V6 car. Although since both are RS models, they may be one and the same. Like John said, it's probably a 32mm bar, tops. I also DON'T think that adding/upgrading sway bars should be the first thing you do in search of a better handling f-body. These cars are 30+ years old now and tend to need a little R&R before going gung-ho swapping in bigger this and that in the name of better handling. You'd be surprised what a good (or just new) set of shocks/struts can do for a car's ride and handling.