Complete GM F41 suspension upgrade

Ok guys. I've finally put together a complete list of P/N's for a GM F41 suspension upgrade, which I currently have on my car.
These parts are all taken from a 2005 Park Avenue Ultra with the optional Sport Handling package. No, it was not standard. As for fitments, I'm not exactly sure if '95 and '96 Rivs can benefit from the springs, so please do your research before attempting this.

This entire upgrade can be done without any modifications whatsoever. The only mod I suggest is bending the rear self leveling bracket to add a little more air into the rear shocks. Everything is bolt on and go. Here we go...

FRONT SUSPENSION

Springs P/N 22197216
Sway Bar (30mm solid) P/N 25649664
Sway Bar Insulators P/N 25699778 (you'll need 2 of these)
Sway Bar Insulator Clamps P/N 25699779 (you'll need 2 of these)

Factory end links will work, however I chose to simply replace the bushings with a sleeve of Energy Suspension Urethane bushings that I bought at Pep Boys. There are many different ways to upgrade your end links....


REAR SUSPENSION

Springs P/N 25655478
Sway Bar (20mm solid) P/N 25650388
Sway Bar Insulators P/N 25650389 (you'll need 2 of these)
Sway Bar Insulator Clamps P/N 25689592 (you'll need 2 of these)

Again, factory end links work just fine. All I did was buy Urethane bushings and used factory links.

Struts are the same. So I guess your strut choice is up to you. I used Delco struts, well, because I work where I do. My car is the Guinea Pig for this setup. I completed it last fall without knowing exactly if it would work. I can tell you, it does. I love it. Pair this entire setup with a Front Strut Brace, and you've got yourself a factory ride height, stock looking beast. Straight line handling is tight, without being jarring. It rides very, very nice. The car is now stable upwards of 130mph, and I get minimal body roll turning corners (unless you're hitting a corner at 70mph).
The road to my dealership has 2 very sharp curves in it. Most cars can only go 40mph through them. I can do 55mph without a problem, and stay in the same lane. One of the salesmen here has a GTO (newer one) he thinks handles good...he couldn't keep up with the Riv

Any questions, this is the thread to do it in.....Enjoy!

Thanks man!

Just put.a.parts request in at local buick dealership, wonder how much both sets of springs cost.lol

highwaywarrior wrote:

Thanks man!

Np. Sorry it took so long. I know for a fact that nothing will be in stock. I had to order everything. The Sway bars came from 2 different states, the springs I got from Lansing, Mi (GM distribution), and the clamps/bushings are probably stocked at local GM suppliers.

Cool

Fantastic! Thanks for the write-up. This is a great "one stop" reference.

I guess someone will just have to test if the FE41 front springs will work on the 95/96. From our previous posts, the rear springs are a match for all years but the 95 and 96 front springs may be different as the part numbers are different. Why, not sure. See part numbers below as an example.

ACDelco Coil Springs (RockAuto)
1995 & 1996 front 45H0354
1995 & 1996 rear 45H2107
1998 front 45H0286
1998 rear 45H2107

Strut (RockAuto)
1995 & 1996 503353 (ACDelco), 236007 (KYB)
1998 22064763 (ACDelco), 335045 (KYB)


If we get the Addco group buy going, I'll probably go ahead with those bars versus the FE41 bars as it will be affordable. But I am curious about the F41 springs. I wonder if the perch or other mounting is actually different, or maybe just spring rate? The struts are different too though *shrug*

Worst case, I wonder if it would be somewhat helpful or conversely cause unpleasant handling irregularites if one put the FE41 springs just on the rear of a 95/96? Any thoughts?

Someone may just have to try or at least compare a 1995 front spring beside a 1998+ spring to see if the dimensions and construction are the same. Would be great to see a 95/96 front spring photographed and measured beside a 97+ front spring.

Thanks again! This is great info.

Al

Juat got email from buick: special prder item, 150 each front spring, 118 inch rear spring, i will do it

Thanks again for this, Scott.

Is Abaddon the only one to install F41 sway bars?

Just ordered the front bar, bushings, and brackets for $155.70 shipped.

Not sure. It think one of the differences between these and Addcos are bar thickness and hollow vs. solid construction. The Addco bars are both slightly thicker, and both solid all the way through. The F41 front may be hollow. It is typical for GM front bars to be hollow for weight savings, hence the larger diameter. I wouldn't be surprised if they did the same for the PA Ultra sport package.

This is still a good upgrade for the money no doubt. I recommend using a hard urethane bushing up front, and a big link kit all around.

I highly doubt the bar is hollow. It's heavy as hell. No, I'm not cutting it in half....
I don't think anyone else has tried it. I started researching other GM bars that would fit the Riv back in '07 or '08. I've had them installed for that long.

Okay, maybe it is solid. I've read about it and no one seems to know for sure. I do know GM put hollow front bars on the F-Body Camaro, and C5 Corvettes including Z06. Just saying it would be an unusual move for GM to do a solid front bar for any sports car from this time. The PA is heavier, so maybe they made an exception here.

Interesting link claiming the F41 term gets misused. For example, there's a 22mm rear bar out there (bet it's the same as for STS):

http://www.elcaminocentral.com/archive/index.php/t-5319.html

Reading this doesn't say for sure, but sort of implies the smaller F41 bars are solid. Also there's a 36mm hollow bar out there that is very stiff and light, and hard to find:

http://gbodyforum.com/viewtopic.php?p=316915#.Ub4houuxI7C

According to this, GM made a solid 30 mm bar for early '90s Camaros. Good enough for me:

http://www.thirdgen.org/techboard/suspension-chassis/84259-sharing-some-spring-swaybar.html

General Motors calls it an F41 Sport Tuned Suspension for the Park Avenue Ultra. It's listed as such in the catalog. For some reason, I think it sounds like my upgrade is trying to be dis-proved. Please correct me if I'm wrong. I've done all the paperwork, all the cross referencing, measurements, and actual on car research for this. Every part number and description is directly from our parts terminals at the dealer. The entire above setup is on my car now.
I really don't see the need for further discussion about it really. It works, period.
Nobody here knows the difference between my setup and the Addco bars, nor will I know because I'm not buying another bar and swapping it out. I wanted GM parts, and I found the ones that work perfectly. I don't claim that this is stiffer or softer than Addco, but Addco doesn't make springs either.

Relax, I was doing a little research for you. In the first post you mention the rear bar is solid, but you don't say for the front bar. Kind of says you aren't sure. When there's missing info like that, I think it helps to make it clear for others deciding between this set and spending more on the Addco set. I was being skeptical, and I would expect you to do the same whenever there's any grey area.

If I were looking to buy this set, I'd want to know 100% if that front bar is hollow or solid. Right now it seems you're the only one with this set on a Riv, and it looks like a few members are interested it this. Saying it's "heavy as hell" doesn't mean a lot unless you have a hollow bar of the same size to compare it too. An actual weight would have helped here.

BTW, the links I provided support your thinking the bar is solid. I'm helping to prove, not disprove your upgrade. We did the same kind of research for the Addco set. No one knew exactly what we were getting at first.

I'm relaxed lol. You're right about the info, or missing info. I always seem to forget that EVERYTHING needs to be provided, and if something is missing, you're definitely going to be the one to question it. That's not a bad thing, it just reads contradictory sometimes...that's all. I also forget that none of you have access to the actual GM parts catalog that I do. Unfortunately, I can't copy and paste pages or images of it. Same goes for our Service Information.
So, I suppose I should be a little more descriptive with my listings.

Robo, I'm not a good example of cost. Charlie actually found out that GMpartsdirect sells the stuff for cheaper than I can even buy it for at my dealership. I believe he got the front bar, bushings, and brackets for ~$150.

ok.but ya gotta buy the springs an all right?

The springs complete the setup, yes. However, just installing both bars and bushings, it makes a HUGE difference in cornering. Add a STB to that, and it's even better. The sway bars alone don't really change the straight line handling. It's the springs that really firm up the whole thing. I just looked up the front springs on GMpartsdirect, and they sell for ~$90 a piece.

I did some quick shopping and found gmpartsoutlet.net to have the best deal for the front bar, bushings, and brackets shipped.

I plan on doing the addco in the rear. Still wondering what those ranchos feel like back there.

Anyone with Ranchos going to be in Lexington on the 27th?

Maybe Jack the R.

Front F41 bar & new bushings feel amazing. I wish I could try the Addco to compare.
I think just a little firmer and it might be perfect.

Wondering what cornering will be like once the back is upgraded.

One thing your fail to mention is that the spring p/n are the same as 1997 OEM riviera springs, so not everyone should be running out to buy them.  They are shared by G platform, and are also on the regular lesabre, aurora, etc.  For example, the front 98 Riv is 22197212 which is shared with the P/A "soft ride".  

Back when we were just a subsection of regalgs.org, I had made a spreadsheet with G-body suspension components.  The long and short of it was that several parts (e.g. the rear lower control arms, and bushing clamps) are the same across the G platform.  I started working on the part number list and came to the same conclusion that NONE of the factory stuff is going to be firm. Even the STS and SSEI seemed to be weak as they were the same as the standard suspension level springs.  I think that spreadsheet is on my old tower, so I'm not likely to find it again.  However I was never able to find the spring rates like GM used to publish in the parts catalogues.  If you have access to that, it would be worthwhile for you to post the spring rates for the various G-platform cars.  You may need the 3 letter spring designator associated to the spring.

Abaddon wrote:

Nobody here knows the difference between my setup and the Addco bars, nor will I know because I'm not buying another bar and swapping it out.[...]I don't claim that this is stiffer or softer than Addco, but Addco doesn't make springs either.

Math knows: the addco is stiffer.  Assuming you install it on a 97 riviera, that the GM "F41" bars are indeed solid, and that you are using similar bushings:
front:  (32^4)/(30^4)=1.29, or 29% stiffer
rear: (22^4)/(20^4)=1.46, or 46% stiffer

That is assuming the bars are solid.  It's not impossible, I have GM cars with solid swaybars (I used to think the Riv bars were solid), but we know that the STS rear 22mm bar is hollow, and the stock riviera bar is hollow.  A 22mm hollow bar is only 5% stiffer than a solid 20mm bar.  I don't know how cost efficient it would be for GM to create a 5% (for all practical purposes identical) stiffer bar for JUST the STS.  The move would essentially be for the weight savings.

So Jason, are you suggesting that mybe the 97s came with stiffer springs from the factory than any other year?

I never bothered to look at a '97 Riv spring, as I was looking specifically for the PAU Firm Ride springs. You are correct, the '97 Riv has those P/N's listed as the springs. News to me, and weird
I knew the springs showed up for use on the LeSabre (rears), but in the GM parts catalog they're listed as "towing" springs. I think the big difference between the '97-'98 platform is the strut. They are different, and the P/N's confirm that.
I know for a fact that a '97 Riv isn't nearly as firm as my car, or any stock Riv for that matter. So, the next question is, what's the difference between '97 and '98 suspensions? Did they change the geometry? Is the strut "longer" on a '97, making the spring seem mushy? That would make sense why the spring might be stiffer on a '98. I honestly don't know. I guess I have more research to do on that.

Nice catch

I posted a link on page one where it's suggested the term "F41" gets tossed around a lot. Depending on the car, there's a range of suspension firmness that can be expected. Same goes for the general term "soft feel", imo. We really can't compare the two - even knowing the spring rates.

The '98 got a new control arm design where both bushings pivot about the same axis. '97 and earlier had a vertical axis front bushing. Combined with the new strut, this impacts the behavior of the front suspension; not sure how much.

Automotive News report from Sep '97, re: the '98 Riviera:

"Improvements in steering and suspension for less body roll and improved highway steering."

The '98 springs could have been stiffer, softer, or the same rate as for '97. But it's not that relevant imo because the application may be different. We need to know the damping rates of the struts and the spring angles. In theory, even if the '97 had higher rates, the effective rates to the wheels could be different than expected.

Here's a good read on spring rates vs. wheel rates, and the factors that impact them:

http://the320i.blogspot.com/2011/03/spring-rate-vs-wheel-rate.html

I like this part:

"This is one reason you see big anti roll bars on luxury cars, you can get away with much lighter springs and still deal with road irregularities if you have a beefy anti roll bar. This makes the ride softer when you are just lumbering along on smooth roads or on the freeway.

This is also why you see such small anti roll bars on F1 cars. They run such heavy springs that chassis flex and pneumatic tire deformation happens before the spring compresses, so anti roll bars don't really add much."

So to achieve less body roll from '97 to '98, did Buick beef up the sway bars to offset a drop in spring rate? Did they keep the sway bars the same and increase spring rates? Did the new control arms have a slightly different spring angle, creating a higher wheel spring rate?