Complete GM F41 suspension upgrade

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?

Makes sense. Should I add a '98-'99 only into the title? It works for '98 and above. I guess it leaves the '97 out of the picture as well. The mod really does work. I apparently dropped the ball a bit because I never looked at the '97 stuff.

With the F41 bar up front, what can I expect in cornering if I add the back bar later?

How much more can body roll be reduced if I add a back bar? I was thinking of doing the ADDCO in the rear.

I pulled out on a wet rainy street after work yesterday and had an enjoyable amount of oversteer. I thought for sure it would have been reduced after putting the F41 bar up front?  

I'm not sure exactly. With the Eibachs installed, it's hard to tell. It just might give you a little understeer, as the rear of the car won't lift as much, and might try to push you through a corner. Or, it could be the best thing since sliced bread lol. I haven't driven in a Rivi with Eibachs yet, so I can't say yay or nay about it.
If the springs on your car are anything like the Eibachs I had on my T-bird, adding a bigger bar in the rear would make it ride like a damn go-kart. My Bird hugged the road like mad. It was quite uncomfortable to drive for long periods.

Typically a stiffer rear sway bar increases the tendency for oversteer, all else being equal. The effect will be slightly less with the Eibachs + stiffer rear bar vs. OEM + stiffer rear bar, because you're adding the bar to already stiffer springs. It's debatable whether the oversteer is a result of increased front traction, or decreased rear traction. I like to think a stiff rear bar helps the front end stay better planted, resulting in more overall grip, but I've talked to people who feel it is more a trade-off between F/R axles.

Charlie, it's good to do the front bar first like you did. The front bar prevents the front end from rolling so much. Now adding the rear bar you can dial in a bit more oversteer without the front end acting sloppy. Safer approach, imo than just slapping on a stiffer rear bar hoping for mad oversteer.

I was playing again today and I am afraid that it's perfect right now.
I would like to tweak and tune and experiment with additional bars, but really, it feels amazing.

The back kicks out just enough that I can let off the gas and put her right where I want her.

I wish you guys could test drive it. Feels great.

If I do do the rear bar, I'm thinking either leaving it and just doing new bushings, or just the F41 bar.

The addco might be too much.

If it feels good, I'd stick with it. There's no rule that says you need stiff springs AND the stiffest sway-bars. Your car could grip better now just with the Eibachs than with stiffer bars. I have the Addcos with OEM springs and I have no desire to go any stiffer for daily driving. It's too much.

There's a happy medium for our cars where it gives the most grip for everyday roads. If you exceed the optimum combined rate (springs + bars), the wheels can start lifting off the ground over bumps, causing the car to laterally "skip". The optimum rate depends on the road surface. If you're not on a smooth race track, the result is less grip in the corners. Plus it can be uncomfortable.

Another downside to very stiff front bars: you can bend the supplied brackets when you really push it. Maybe the F41 front bar isn't enough to cause this, but a couple of us with Addco bars have seen the need to upgrade to UMI Performance CNC machined brackets. If you're able to use a standard bracket safely, and you like the results, why use a bar that requires more expensive brackets. I'd say you're sitting pretty well right now.

Let's not forget AA, you're in Ohio. Home to the worst roads in the country.

i think thats a tie between new york and baaastan i hate both their road systems. ohio not so bad. md traffic full of idiots at rush hour but otherwise ok, ky waatch out for deer! lol i can go on i been all over

Quote :

Let's not forget AA, you're in Ohio. Home to the worst roads in the country.

Ours aren't great, but you haven't seen bad roads until you visit MI, just a few miles from Charlieparker's neck of the woods. It seems the closer you get to Detroit, the more likely you are to get swallowed by a giant pothole.

charlieRobinson wrote:

The back kicks out just enough that I can let off the gas and put her right where I want her.

My car does the exact same thing. Only difference being I have to use the throttle to straighten the car out. If I let off the throttle to hit a corner hard, you can feel the ass end want to come around. Just a little feathering of the throttle straightens it right back out.

AA wrote:

Ours aren't great, but you haven't seen bad roads until you visit MI, just a few miles from Charlieparker's neck of the woods. It seems the closer you get to Detroit, the more likely you are to get swallowed by a giant pothole.

You're not lying. Michigan roads suck ass. Oddly enough though, the further North you go, the better they are. They don't use salt in the winter up north....they use sand.
That, and anywhere near Detroit doesn't have enough money to keep up the roads. We have 3 major cities in Michigan with emergency financial managers....

Nothing better than crossing the border into ohio on the highway from Michigan and immediately feeling the difference in road quality.

The roads around me that I'm on aren't bad at all. I'm happy with them.

I remember on my way up to visit AA. "Welcome To Ohio" WHUMP WHUMP WHUMP WHUMP.

OH isn't perfect by any means. I have to steer around some crap every day. We also sink our man hole covers about 3" under the road surface, which sucks. Avoid those, drive in the good parts of town and you're fine. When I go up to southern MI, I see this kind of stuff and it freaks me out a little.

I can second the notion that MI roads are awful. Detroit is bad, but try going to the middle of nowhere in lower Michigan, they call it the "Irish Hills" area. You might as well drive on the moon.

Chicago roads are pretty shitty as well. Sink holes pop up on occasion in the middle of a residential area