Write-Up: Front/Rear (Addco) Stabilizer/Sway Bar Installation

I'm going to guess swaybars aren't engineered with the idea of shifting the weight balance of a car, although I've got no argument with the idea of a perfect 50/50 weight balance. If we're talking about using a solid rear bar instead of a hollow rear bar, all else being equal besides weight, IMO engineers would rather have the weight savings and a miniscule improvement in fuel economy. CAFE regulations being what they are.

The question is, why do we see the consistent use of lighter, hollow bars up front, and heavier, solid bars in the rear? If the object was to reduce weight overall, we'd see more hollow bars in rear, as they're lighter for a given torsion resistance.

If the object was only to use stiffer torsion rates up front, the easiest way is to use a thinner, solid bar. But you don't see that very much. What you do see is lighter, hollow bars up front. They're trying to lighten the front end of the car.

While it may seem like a single part weighing 15 lb may not matter much, when you add up a few hundred parts, it makes a huge difference. I once visited an R&D lab used by one of the big 3 where the engineers were spending lots of time and money developing a plastic oil dipstick - for the purpose of weight savings. I think they were trying to save about 3 oz in that case.

If we've got weight to spend in the back, why put it in a sway bar, and not into useful structure? Why not a chassis stiffener instead?

The addco swaybars are solid and measures 7/8" (22.2mm). The ones they sell are different from the bars used by GM.
I will have to plug in my desktop tonight. I have the specs for all the g-body bars. IIRC, the only production vehicle to use a 22mm bar was the STS, and it is hollow. I believe the F41 package gave you a 20mm solid rear bar.

Jack the R wrote:

Abaddon, is the GM front bar solid as well?

Do we know that the GM bars are not actually the same bars as Addco?

The front bar is solid, only the rear is hollow. It's even listed this way in the GM parts catalog, along with the diameter. Mind you the smaller bars on the rear (our factory 17mm) is hollow, the larger 20 or 22mm you can get are solid. I made sure of this before I purchased them.

Go back to page 10 for the P/N's of the GM F41 bars......I can also get them at a descent price, but you'd be better off getting them from MonsterParts if you can get the shipping free.....

Abaddon - Now I'm confused. You're saying the PAU front bar you got is solid, and the PAU rear bar is hollow? And the rear bar is 20 mm, not 22 mm?

Sorry for the confusion....The stock rear bar on the Riv is 17mm hollow, and the front is solid. The PAU F41 bars I installed are both solid. I just went outside and measured them with my micrometer....the front is roughly 31mm and the rear is roughly 21mm (1mm of paint?).

So, I guess to answer your question, both F41 bars are solid.....

Maybe the Addco front bar is solid. I don't know how to tell for sure.

AA, have you got a micrometer handy? How about measuring your bars?

turtleman wrote:

Can anyone speak for the addco bars being tighter than the F41 or even the FE2/3 bars? They are the same dimensions so someone would pretty much have to literally compare them either on the car or something like what AA described for a test. Has anyone experienced both kinds? Addco claims that their bars are tighter than any of the applications, including the cars with the FE2, etc bars so logically, that says the Addcos are the tightest but is there any more knowledge of this besides Addco's word?

I already have FE2 bars (rear installed - front waiting) but I want the tightest I can possibly get.

I could, but I assume no one would read it. This is why cramming every post made about a subject into a single, unsearchable thread doesn't make sense to me. The info has been around since we were on regalgs.org. It also hilights the flaws of the ± system. If people are giving +++ to erroneous information, some members (the ones who skim through threads) will fall upon it and use it and/or perpetuate it.

1) the addco bars are solid. Period.
2) they measure 1.25" and 7/8". I measured them with a vernier, along with the stock bars when I did the swap.
3) The swaybar diameters originally listed by abaddon are incorrect (Thanks for going to measure to correct, but it would be great if you could edit your original post). They are 30mm and 20mm front and rear, respectively. I originally pulled this info from the gm parts catalog.

The FE2 suspension components are NOT a viable, cheap alternative to addco swaybars as some posts might suggest, though they are stiffer than stock. They are stiffer than stock, but possibly not enough to justify your time and money unless you score them for very cheap.

I have never heard of the stock sway bars being hollow. That's not to say that it aren't, but I am 99% sure the stock 17mm rear bar is solid. I just went to check my fiancée's stock riv and tapped on it with a mag lite. It sounds solid to me, but it's still attached to the car. Although I swapped out the stockers for the addcos a few years ago (07), nothing indicated to me it was not solid. The stock one looks like a coat hanger, but it's only 2/3". If someone has the stock rear off the car, please rap on it to confirm. If not, I will cut this one in half to lay this to rest once the owner of my previous riv returns my Addcos. Regardless, assuming the wall thickness is .25" the difference is negligeable (i.e. 2%).

Scott, just to confirm, you are aware that when it says "holl" next to a p/n such as a swaybar it just gives you the "Hollander" interchange number ? It's not an abbreviation for hollow. If you do have a gm parts catalog that specifies the 17mm bar is hollow, please post it. I saw no such info in the parts catalog when I looked in 06.

The largest front bar gm offered for the G-body was 30mm (FE2/FE3). The largest, and stiffest, rear bar GM offered was 22mm hollow. If you can get your hands on the FE3/FE2/F41 front and FE3 STS rear bars, I think they would make a great upgrade if you can get them for cheap. I believe it is safe to assume a wall thickness between .125" and .25" for the stock STS rear FE3 bar. Most hollow bars I have seen had .25" walls, and lets face it, GM wasn't going to produce a bar that is softer than their 20mm OEM bar. So the addco bar isn't much stiffer than the STS OEM bar.

==== edit: stiffness figures edited to account for stock bars being hollow =======

for reference:
assuming all OEM rear bars have a 3mm wall thickness; and
assuming all OEM front bars have a 5mm wall thickness

30mm front is 27.5% stiffer than the 28mm stock front
20mm rear (FE2) is 76.5% stiffer than the stock 17mm rear
22mm rear bar (FE3) is 144.9% stiffer than the stock 17mm and 23.1% stiffer than the FE2 20mm rear

02018 1.25" (31.75") front ADDCO: 99.4% stiffer than the stock 28mm bar or 56.3% stiffer than the 30mm bar. This is considering they have the same overall and lever length. The addco had a very slightly different bend to them, but it should not affect stiffness dramatically.
02015 7/8" (22.2mm) rear ADDCO: 254.2% stiffer than the stock 17mm bar, 62.7% stiffer than the 20mm bar or 44.6% over the FE3 rear bar

Rickw wrote:

I have no argument whatsoever regarding the effective measurement of one sway bar over another. It certainly can not be compared by outside diameter only, I agree.
But what I experience with the ADDCO rear bar ( in this somewhat stock configuration) is a reduction if not almost complete elimination of understeer from the front
So I've been slightly apprehensive as to what to do the front, without reversing the progress i made.

As you can see, the upgraded front bars provide substantially less stiffening than the upg rears, so you won't be going back to the stock "proportion" regardless of whether you go to a 30mm or addco front. I think you will find that going to an addco swaybar will give you a very nice balance but, as I previously stated, if you can find a 30mm bar on the cheap, go for it. Just keep in mind it isn't pleasant to change and you'll probably only want to do it once

Is the F41 bar an FE2 or FE3 bar?

I got the front Addco bar yesterday. That thing is heavier than hell! Judging by the weight compared to the FE2 bar I have here, there's no doubt its solid.

If you aren't going to do anything with the OEM bar, would mind cutting it in half?

Why cut the bar in half? Unless you just want to find the wall thickness if it is infact hollow.

Weigh it, the density of steel depending on alloys is 0.280–0.291 lb/in3., compute the volume of the anti-sway bar as best you can. (would be easier if it was a straight cylinder of course) Do the math and see how the numbers come out. The difference between a hollow and a solid anti-sway bar of the same OD should be quite a bit.

If I had the stock one out of my car I'd do it myself for fun, but...

Cheers.

Thanks for the info on the end links. I'm debating changing out the front bar, but will at least most likely change out the rear bar.

Quote :

Why cut the bar in half? Unless you just want to find the wall thickness if it is infact hollow.

Weigh it, the density of steel depending on alloys is 0.280–0.291 lb/in3., compute the volume of the anti-sway bar as best you can. (would be easier if it was a straight cylinder of course) Do the math and see how the numbers come out. The difference between a hollow and a solid anti-sway bar of the same OD should be quite a bit.

I know it can be calculated, but I just want to know if the OEM bar is hollow. I suspect it is. And cutting it would seems easier vs. calculating the exact volume of the bar, as it's no where near straight.

Maybe you could calculate a theoretical thickness, then we'll see what the actual measurement is after it's cut?

I am probably missing it somewhere, but what are the Addco part #'s for the front and rear bar (kits) for the 95-99 Rivieras? I started looking through this write up, but didn't immediately see them. I am sure they are somewher.

They should be in this write-up. Take a closer look.

You ever gave the Red Mark to my reply...... I'll just say that when I joined this site I didn't expect someone to spoonfeed me information.
I spent month's reading and taking notes before I even made a post and most of my posts by then was to help people with what I learned.

I'm sorry if I forget the P/N's of the damn Sway Bars. But I repeat, if you look through the thread they are here. What is the problem with that.

Larry, you have a problem with reading or is it just easier to dis someone and get what you want.

I'll saw this FE3 up. Nobody needs it. I'll barrow a mic from somewhere and measure it.

Rickw wrote:

They should be in this write-up. Take a closer look.

I know Rick, I was too lazy to look through all 12 pages , and thought someone would know off the top of their head. I now know the rear bar is part #2015. Need the front bar part #

Rickw wrote:

They should be in this write-up. Take a closer look.

You ever gave the Red Mark to my reply...... I'll just say that when I joined this site I didn't expect someone to spoonfeed me information.
I spent month's reading and taking notes before I even made a post and most of my posts by then was to help people with what I learned.

I'm sorry if I forget the P/N's of the damn Sway Bars. But I repeat, if you look through the thread they are here. What is the problem with that.

Larry, you have a problem with reading or is it just easier to dis someone and get what you want.

Rick,
Why are you giving me attitude? Are you having a bad day? You would not say that to my face, so why are you saying it from behind a keyboard?

I'll copy this here in case you didn't see my post from above.

You ever gave the Red Mark to my reply...... I'll just say that
when I joined this site I didn't expect someone to spoonfeed me
information.
I spent month's reading and taking notes before I even
made a post and most of my posts by then was to help people with what I
learned.

I'm sorry if I forget the P/N's of the damn Sway Bars.
But I repeat, if you look through the thread they are here. What is the
problem with that.

Larry, I'm not giving anyone a hard time nor do I have an attitude. Read the words.

What is the red Mark? And I know attitude when I see it.

I enjoyed this mod so much I ordered another set for Melissa`s white riv. After driving both rivs back to back for the last few months, this mod makes a significant difference in handling. Even Melissa can easily tell the difference and prefers the suspension on the green riv. I would say it's definitely an underrated upgrade.
But first, I need to subtly slip on just the STB on her car to see if she'll notice a difference...

^^^ I agree. I knew there was some difference, but I didn't realize the full potential until I autocrossed last summer. The car doesn't roll as much, and the handling seems more nimble when you change directions.

Absolutely fantastic handling mod for the price. You can take corners soooo much faster. Car is wayyyy more stable too.....love it.

(I know I've said this once before...deal with it )