Stock sway bar diameter sizes on IROC's
 

After a lot of going back and forth I've decided to rebuild the stock suspension on my 1988 IROC after I get some money saved up.

I've already installed Hotchkis subframe connectors, lower control arms, panhard rod, and a BMR torque arm. Other than those changes my suspension is all stock.

I'm going to get some stock replacement springs (probably from Moog) and Bilstein shocks & struts. I'm also going to rebuild the steering system as well - probably with some more parts from Moog. Then I'll install poly bushings all the way around.

My question is about the sway bars - what diameter came stock on IROC's. I've read in different magazine articles (from when thirdgens were new) that the diameters changed for different years.

Was there a standard set of sway bars that was used for a car with the LB9 or L98? Or was sway bar diameter a computer selected parameter (like the factory springs were selected) based on the options that a particular car had.

Re: Stock sway bar diameter sizes on IROC's
 

I Think from 85-?? the front was 34, and rear 22. and ?? - 92 36 & 24 IIRC Some 1LE's got 23 rear sway bar to correct an under-steer in the Players Challenge.

Honestly I do not remember if it was 88 or 89 when it changed... I do recall that the WS6 cars got the 36/24 starting in 86, HOWEVER the Iroc got the "Wonderbar" and the Firebird didn't...

Re: Stock sway bar diameter sizes on IROC's
 

Thanks for the reply. Thats what I thought - the WS6 Firebirds got the biggest factory sway bars 36mm in the front and 24mm in the rear.

Re: Stock sway bar diameter sizes on IROC's
 

My 85 IROC was equipped with a solid 34mm front and 24mm rear.

JamesC

Re: Stock sway bar diameter sizes on IROC's
 

Was 22mm a stock rear size for a third gen? I've commonly seen 23 and 24, and many of the early Z28's had 21mm rears. I don't even see an energy suspension bushing listing for 22mm.:huh:

Re: Stock sway bar diameter sizes on IROC's
 

Maybe it was 24... My bad.. I would have to go through the parts catalogs again...

Re: Stock sway bar diameter sizes on IROC's
 

1982, 9 (f/r)
Base - 27mm/12mm
F41 - 29mm/12mm
Z28 - 31mm/21mm

1983, (f/r)
Base - 27mm/12mm
F41 - 29mm/12mm
Z28 - 31mm/21mm

1984, (f/r)
Base - 27mm/12mm
F41 - 30mm/12mm
Z28 - 32mm/21mm

In 1985, (f/r)
All cars except Z28 - 27mm/18mm
F41 cars - 30mm/18mm
Z28 - 32mm/23mm
IROC-Z - 32mm/24mm

The 1986 cars got: (f/r)
Sport Coupe - 30mm/18mm
Berlinetta - 27mm/none
Z28 - 34mm/23mm
IROC-Z - 32mm/24mm

The 1987: (f/r)
All Coupes - 30mm/18mm
Z28 - 34mm/23mm

1988: (f/r)
Sport Coupe - 30mm/18mm
Z28 - 34mm/23mm

1989: (f/r)
Sport Coupe - 30mm/18mm
Z28 - 34mm/23mm

In 1990, (f/r)
RS - 30mm/18mm
Base IROC-Z - 34mm/21mm
16" rim IROC-Z - 36mm/24mm

In 1991, (f/r)
RS - 30mm/18mm
RS with 16" rims - 34mm/21mm
Base Z28 - hollow 34mm/21mm
Z28 - solid 36mm/23mm

The MVMA report for 1992 does not list anything for stabilizer bar. I would assume that 1991 and 1992 would be the same.

Re: Stock sway bar diameter sizes on IROC's
 

Why is there an IROC-Z category for 1991? Thanks for posting though, I'm glad to see that there is yet another factor making the 1990 IROC the cream of the crop. ;)

Re: Stock sway bar diameter sizes on IROC's
 

Thanks for the information Scott. That really helps me out a lot. At least now I know what should be under my car when I go under and start measuring for some new poly sway bar bushings.

Is there a reason the later 1990-1992 IROC's & Z28's got bigger sway bars than cars made earlier from 1982-1989?

Did the later thirdgens have softer spring rates than the earlier cars so GM made up the difference by installing bigger sway bars on these cars?

Re: Stock sway bar diameter sizes on IROC's
 

Humm, well, that info throws me for a loop as I've never heard of an IROC with a 32mm front bar. Perhaps I haven't been paying attention.

JamesC

Re: Stock sway bar diameter sizes on IROC's
 

http://www.iroc-zpostforum.com/NewsIROC350.htm

This link is to an old magazine article for a 1987 IROC with the L98. Says this car has a front sway bar diameter of 34mm and poly endlinks.

I thought that thirdgens didn't come stock with any kind of poly materials.

Also says that for 1987 the rear sway bar was reduced from 24mm to 23mm due to the addition of a poly bushings used on the rear sway bar.

The the rear sway bar diameter was reduced because the stiffer rear poly bushings on the sway bar made the car oversteer slightly during quick manuvering situations.

Re: Stock sway bar diameter sizes on IROC's
 

My 1990 had blue stabilizer link bushings from the factory. I'm assuming that blue is not regular rubber. Squirrels chewed them completely to bits, must have been good since they didn't touch anything else on the car.

Re: Stock sway bar diameter sizes on IROC's
 

https://www.thirdgen.org/1985_IROCZ_..._November_1984

This is a link to a 1985 IROC with the LB9.

Says the rear sway bar diameter is 24mm and that was 1mm larger than the non-IROC option Z28 rear sway bar.

Re: Stock sway bar diameter sizes on IROC's
 

My 1983 Daytona 500 Edition Trans Am with the WS6 package.
1-1/4 front / 13/16 rear

Re: Stock sway bar diameter sizes on IROC's
 

32mm / 21mm Many times The Firebird got the upgraded suspension before the Camaro.. The WS6 for example, IIRC starting in 1986 (maybe 1985) the sway bars were 36mm & 24mm for WS6 equipped cars, and it was not until 1990 that the IROC got the 36/24

Re: Stock sway bar diameter sizes on IROC's
 

See post #9
https://www.thirdgen.org/forums/susp...iscussion.html

Re: Stock sway bar diameter sizes on IROC's
 

My guess would be that the sway bar sizes generally increased as tire sizes grew.

Re: Stock sway bar diameter sizes on IROC's
 

That was true, and for the most part you can point to when they increased the size of the wheels, the size of the bars did increase. I think it was less because of one caused the other as much as when you increase the size of the wheels, to get the benefit of having those larger wheels you need to change other suspension components in order for the larger wheels to actually matter more.

The thinner the sidewall of the tire means that the suspension has to actually work more to do the same trip, obviously a taller tire would mean that the tire absorbs more of the energy from a non-perfect road. To change the tire, and not the suspension would only give you partial benefits to the larger tire, likewise to make the sway bars larger without changing the size of the wheels, would also be less beneficial than doing both.

Another thing to consider is larger sway bars with smaller wheel diameter may not have the desired results that someone would expect. Like mentioned previously the tire absorbs a lot of the road, if you put too large of a sway bar with too small of a wheel, the loads put on the tire may not be appropriate or good for the tire.

The Larger 16" wheels also had the added benefit of having a larger patch of tire that came in contact with the road. Ideally if a 245-50R16 tire would have 60,000 square mm of contact with the road, then a 215 wide tire would only have about 45,000 sq.mm in comparison. Without trying to figure out the exact math, the the lateral friction the tire would be able to withstand before sliding would have increased by about 1.3x. I suspect that it is something that has diminishing returns, A 12" wide tire will definitely be able to take more lateral g's than a 6" wide tire, but I am not convinced that with everything else being equal that the difference would be double. Of course I might be wrong and it might be more than double. Then you have to worry about wet surfaces vs dry surfaces and a myriad of other things to consider...

IIRC magazine articles of the day claimed a lateral .9g to .93g with the 3rd generation F-body. Which is still impressive when comparing numbers with some of the cars of today.

Re: Stock sway bar diameter sizes on IROC's
 

Thanks for the info. Even today I still surprise people that yes a thirdgen factory high performance model (Z28, IROC, Formula, Trans-Am etc.) with stock 16 inch wheels and good z-rated tires is able to pull a little over 0.9'gs. This is without all the magnetic shocks and wider tires that more modern performance cars have.

GM really did their homework when they designed 3rd gens with respect to handling and road holding. I've had my car for over 10 years and I really love how stable my car is. You really have to try to do something stupid to get the car in an unflappable situation. It can be done easy enough if your foolish but, these cars are very stable to start with.

Re: Stock sway bar diameter sizes on IROC's
 

My car would be 31.5mm not 32mm. Were the 36mm 24mm hollow or solid?

Re: Stock sway bar diameter sizes on IROC's
 

The 36mm was hollow, the 24mm not sure... I know that they were hollow more for weight savings than anything. The majority of the torsion is placed on the outside of the sway bar, it has to do with leavers, the center of a twisted rod has close to zero torque, the outside has to move further for every degree of twist, therefore it has to resist more... (I never weighed one) but if you could make a 32mm solid sway bar weigh the same as a 36mm sway bar by making it hollow, the hollow 36mm sway bar would give better performance than a solid 34mm sway bar.

Again this is one of those things that would have to be tested to get real world numbers. I could speculate all day long, but the truth is you need to know what kind of steel it is, how much carbon, iron & other elements. Then you have to know the flexibility of that material, and then you cannot assume that a 36mm tube is not necessarily the same material as the 34mm solid. And you still need to know the thickness of the tube to calculate loads and tensile strengths in order to calculate which is better.

Therefore, to really get the truth about which is stiffer, get one of each in good condition, and put 100# of torque on it and see the deflection, the one that bends the least is the stiffer.

If I also remember right the sway bars are soft steel, they were not made from spring steel, or hardened steel.

John

Re: Stock sway bar diameter sizes on IROC's
 

Here's a roll-up of sizes, but some of the info in this seems to conflict with info posted earlier:

https://www.thirdgen.org/forums/faq-...-sway-bar.html

Re: Stock sway bar diameter sizes on IROC's
 

Hollow/solid.

JamesC

Re: Stock sway bar diameter sizes on IROC's
 

Why 31.5 mm? I have been trying to find out the stock sizes for the early third gen Trans Ams and most sources say 32mm

Re: Stock sway bar diameter sizes on IROC's
 

So how much do you think the suspension as far as the struts go play into that? Is it mostly because of the sway bar size and wonder bar or is it good because the stiffer springs and better struts?

Also. anyone know who sells the 36mm bushing kits? the part store guys can only get 34mm

Re: Stock sway bar diameter sizes on IROC's
 

i measured it and confirmed what the gm dealer said its 31.5mm / 1-1/4

Re: Stock sway bar diameter sizes on IROC's
 

Moog K6459.

Re: Stock sway bar diameter sizes on IROC's
 

Interesting. I've never heard of a 31.5 on a thirdgen.

JamesC

Re: Stock sway bar diameter sizes on IROC's
 

Just put the calipers to my stock 91 B4C (non-1LE):

36mm front
23mm rear

What's odd is the front sway goes from perfectly round to slightly oval on both sides before going back to 36mm right into the bushings. This results in a 37-38mm reading for a brief portion of the bar. This is consistent on both sides of the bar so I can only imagine this is how they were stamped out.

Re: Stock sway bar diameter sizes on IROC's
 

I've got a set of the Spohn chrome moly ones and I just picked up a 36mm hollow and 24mm solid bar from an 89 iroc. Strangely enough the all original tpi iroc had these bars, a WonderBar and a 9bolt dif w/ 2.77 but no 1le brakes or alum driveshaft.
Anyways I'm not quite sure which set to sell and keep. The car is still being put together so I can't test them and the Spohns are brand new so better to sell before I install them. The car in an 88 hardtop with a ls1/auto all adjustable spohn going in...
But the real reason I wanted to post is that I had an 82 FB v6/auto with full interior option load but it had no sway bar in the rear at all. Holes were there with slugs in them for the brackets but not tapped. Installed a bar real easy.
Seeing the original list maybe having no bar was fairly uncommon, maybe not... I think the front was a fair size thou 28mm?

Re: Stock sway bar diameter sizes on IROC's
 

It's pretty common for 82-84 Sport Coupes to have no rear bar. I have not seen an 85 or newer without a rear bar, though. Some early Firebirds have no rear bar, others have tiny bars. Here is a picture of a 12mm rear bar that I pulled from an '83 Firebird SE. It's the only one I have ever come across in that size.

Edit to add - IROC's came with different size bars during their 6-year run. I have seen '85's with solid 34 fronts, while later ones had hollow bars. Most of the rears I have seen on earlier IROC's are 23mm

Re: Stock sway bar diameter sizes on IROC's
 

85 Trans Am got a 25mm rear sway,.... That's the largest rear sway ever offered on a ThirdGen. That car also got a 34mm Solid front bar too. Pretty sure that 85 was the only year that a front 34 solid and 25mm rear sway were offered.

Me either, and I've been under more IROCs than I care to try and remember.

Not accurate,...... that dealer don't know ****. If he looked in the books he would know that's false information. Your 32mm bar rusted and you lost a 1/2mm. Measure again in a couple other spots. ( use a caliper, not a wrench )


Edit:

That just looks funny !!

:driving:

Re: Stock sway bar diameter sizes on IROC's
 

it measured 1-1/4 / 31.5 and the vintage dealer book confirmed
and it was not rusted

Re: Stock sway bar diameter sizes on IROC's
 

:bs:


I see that you re-posted without bothering to actually check. So; I'll do you a favor and show you what the "vintage" ( 82-87 ) GM part number book REALLY says:

http://berlinetta.info/help/FrontSwayBarSize.jpg


No Sway Bar ( Front OR Rear) was ever offered in 1/2mm increments. Regardless of your lack of acceptance to the fact that you are wrong,....... Your stock bar is/was a 32mm.

:driving:

Re: Stock sway bar diameter sizes on IROC's
 

I own a 1983 trans am pace car not a berlinetta
1-1/4 is in inches /standard. That was the measurement

Re: Stock sway bar diameter sizes on IROC's
 

Double post

Re: Stock sway bar diameter sizes on IROC's
 

Berlinetta:

27mm in front
No rear sway bar


I see you just bought aftermarket "1-1/4 front and 13/16 rear energy suspension bushings" for your car last month,..... Those would be the aftermarket suppliers measurements - not factory spec.


http://www.earlythirdgen.com/forums/...php?f=3&t=1348

Some random internet post (& and the GM Parts book ) still not enough for Ya';.....


http://en.wikipedia.org/wiki/Pontiac...rd_generation)

I could post countless other web pages documenting other 83 Daytona owners detailing thier sway bar sizes, but you get the idea. I really don't understand why you would ever thing I was trying to steer you wrong here Chris; What-ever dude. :rolleyes: Just don't be surprised when other people call you out on this......



:driving:

Re: Stock sway bar diameter sizes on IROC's
 

1) We need to calm down, this is not life and death.
Here are the sway bar sizes as per the IPC 1992
FIREBIRD
BASE (FE1)
Front
82-84 27mm
85 30mm
86 (2.5L) 30mm

MID (F41)
30MM
82-84 30mm (Trans Am & S/E)
85 32mm
86-92 34mm

WS6, WS7, WY6, WY5 (FE2)
82-84 32mm
84 Special - 34mm (I assume anniversary Ed)
85 34mm
86-92 36mm

Rear:
BASE (FE1)
82-84 NONE
85-92 18mm

Mid (F41)
82-83 12mm
84 18mm
85-92 21mm

WS6, WS7, WY6, WY5 (FE2)
82-83 2.8L, 2.8-1 - 18mm
82-83 305G,H,S - 21mm
84 21mm
84 Special - 24mm (I assume anniversary Ed)
85-92 24mm

Re: Stock sway bar diameter sizes on IROC's
 

We take our sway bar sizes seriously!:thumbsup::thumbsup:
Seriously, there is one missing from the list. John in RI mentioned earlier the 25mm rear, found on (some?) 85TA (and maybe some 84's). I found one today. First one I have seen, so I snagged it. From an '85 TA, WS6 (16" rims, 4 wheel disk, etc) that interestingly enough, had an LG4. Odd combo. Was a fairly late build, April '85 on the door sticker. Shots:

Re: Stock sway bar diameter sizes on IROC's
 

the trans am handles better with 1-1/4 front and 13/16 rear energy suspension bushings

Re: Stock sway bar diameter sizes on IROC's
 

All I can go on is what the IPC shows...
There are 2 explanations to your findings.
1) There was a 25mm rear sway bar, but there was no replacement part, and it was replaced with a 24mm.
2) it is an aftermarket bar.

Oddly enough, the WS6 & WY6 was called a "Performance Package" and the WS7 & WY5 was a handling package... In theory, you could get WS6 with a V6 on an S/E, as it is specified with having a special rear sway bar in 82-83 the 12mm..

John

Re: Stock sway bar diameter sizes on IROC's
 

Just trying to clear up some of the invalid information that gets posted here - it's a real bitch sorting thru posts when you need answers and keep finding the same "wrong" data mentioned over and over again.

NICE SCORE ! :thumbsup:


I got my 25mm rear sway from an 85 TA,....... It's ready and waiting to get restored so I can install it in 'Mean Green'. I also re-checked and the front sway from that 85 Trans AM & it IS a 34mm SOLID bar. This make/model/year was the only car I've ever found this combination in, however; I've read others stating that the set-up was also used in the 85 IROC too. I have never owned an 85 IROC & not been able to confirm this; my parts book doesn't show a 25mm from 82-87 for Camaro.




:driving:

Re: Stock sway bar diameter sizes on IROC's
 

My 85 IROC was equipped with a solid 34 mm front and a 24 mm rear bar.

JamesC

Re: Stock sway bar diameter sizes on IROC's
 

Thanx for that post Jim - I'll keep that as a mental note !

To help confirm the size/existance of the 85 TA 25mm Rear Sway:

http://berlinetta.info/mypics/GreenCar/25mmRearSway.jpg

http://berlinetta.info/mypics/GreenC...earSwayBar.jpg


:driving:

Re: Stock sway bar diameter sizes on IROC's
 

Although there was a 25mm sway bar, there is no part number for it in my IPC... I would be interested in seeing an older parts catalog from 1985 or 1986... Mine is from 1992, and I know that some things have been deleted, for example the part number for the Aluminum Firebird Hood is missing, there is a reference to (Steel) that is still present, but the Aluminum part number is gone.

John

Re: Stock sway bar diameter sizes on IROC's
 

Also For your enjoyment, I found the 1992 Camaro IPC pages as well... Unfortunately they are on Microfiche, so I have to take a digital picture of them, thus why they are inverted colors.

Re: Stock sway bar diameter sizes on IROC's
 

Here's the info from my "82-87 -'F' Parts" book. ( shows a Camaro on the cover )

http://berlinetta.info/help/RearSwayBarSize.jpg


As you've found with your later version of the parts number books,..... there's no part number for a 25mm bar in this book either. The sway bar information it not continued to the next page, it ends at the bottom of the page shown.

:huh:

I also find it odd that there's no 23mm rear sway listed. I can't even count the number of 87 and earlier Z28's I've owned with a 23mm rear bar on the back.



:driving:

Re: Stock sway bar diameter sizes on IROC's
 

Hello everyone, if this helps any my 1985 IROC originally came with a 32mm (1 1/4") solid front with polyurethane bushings and the rare 25mm (1") rear sway bar. The car is an early production and has a rough cast iron thermostat housing instead of the later smooth steel housing used on later TPI engines. It also has the fog lamp switch in the lower part of the dash instead of being right under the head lamp switch. My other 1987 IROC has the 34/23mm combination, and my brothers old 1989 IROC had the 36mm hollow front and 24mm solid rear sway bar. One time I also came across a 1985 TRANS-AM WS6 in a salvage yard, with a solid 36mm front sway bar lying in front of the car.

Re: Stock sway bar diameter sizes on IROC's
 

Oh, and just one more thing if this helps with any, my 1985 IROC was equipped with the front BZW springs and rear NNN springs which I still have in storage.

Re: Stock sway bar diameter sizes on IROC's
 

Thats good info. I've read that GM changed the rear sway bar size to make the rear end easier to control and hard driving situations. Is it also true that the 1985 IROC's had a tire rub problem in the rear under hard cornering.