FAQ: G-Body Suspension Basics

A strut tower brace wont do anything in the handling dept.It just stiffens up the body.

Wouldn't that reduce body roll though?

c0reyl wrote:

Wouldn't that reduce body roll though?

The main function of the sway bars is to REDUCE BODY ROLL. That is their purpose. Want less body roll? Install bigger sway bars. Addco makes a set of sway bars that are a huge improvement over the stock bars. 1 1/4" in front, and 7/8" in the rear. Installing the Addco bars will get rid of the twitchy feeling you get at the limit with the stock bars. There is a write up on sway bar installation in this forum. I just did this about 2 months ago. It helps immensely, The Riviera is a big car, and it will never handle like a little Honda Civic, but the sway bars will remedy what you are feeling. It won't prevent your subwoofer from moving around though, it might make things worse. Sounds like you need to secure it better. I got my bars off of E Bay.

http://www.ebay.com/itm/Addco-2018-Front-Anti-Sway-Bar-Stabilizer-Roll-/310312093621?pt=Motors_Car_Truck_Parts_Accessories&fits=Make%3ABuick|Model%3ARiviera&vxp=mtr&hash=item48400ac7b5

http://www.ebay.com/itm/Addco-2015-Rear-Anti-Sway-Bar-Stabilizer-Roll-/300547923668?pt=Motors_Car_Truck_Parts_Accessories&fits=Make%3ABuick|Model%3ARiviera&vxp=mtr&hash=item45fa0d5ed4

https://rivperformance.editboard.com/t916-write-up-front-rear-stabilizer-bar-installation

Agree with robo and Larry's comments, especially the part about the subwoofer needing to be secured. Want to add a few things about body roll.

First thing: better understand exactly what body roll is, and why you may or may not want it. Body roll is simply the tendency of the car to lean over in a corner, or tilt on its long axis, like an airplane in a banked turn. All cars roll, some more than others. Key point: body roll shifts more load to the outside wheels vs. the inside wheels, or put another way, it compresses the suspension on the loaded side (outside wheels) more so than the unloaded side (inside wheels). You want some amount of roll in a daily driver, and it's hard to know exactly how much you really have on feel alone. Your sub box moving around in the trunk, and people sliding around on the seats - those are NOT indications of roll - these things are caused by lateral G forces, from the grip of the tires. We tend to think of roll as a limiting factor in lateral grip, and it can be, but in some cases it actually can help.

A BMW M5 rolling in a hard corner:



The M5 shows a fair bit of roll, and that tendency was designed into the suspension from the factory, so that the shocks, springs, and other components do a fair share of the work in the turns instead of putting everything on the tires. This makes the ride more comfortable. The suspension geometry on the M5, like most cars, was designed to do certain things under heavy load (during a hard corner). It's not easy to explain, but there are things happening behind the wheels that we don't see, and there is some good in having the car roll, because it lets the car's suspension adjust to do what it was designed to do. The Riviera's suspension does this, too. In fact, it allows quite a bit, to keep the ride very comfortable as Buick owners expect.

When you use stabilizer bars and stiffer springs, shocks, etc. to eliminate roll, the car's center of mass (body) stays more upright, so weight is distributed more evenly across all 4 wheels, which tends to increase grip. BUT as a result, in a turn the car's suspension becomes less compressed on the loaded side (outside wheels) than it did when stock. This means the suspension isn't fully allowed to function as it was designed to from the factory. So what happens? The tires end up doing most of the work. For this reason, you must have a good set of performance (firm wall) tires on the car in order to take full advantage of suppressed body roll. If you don't, the tire side walls will collapse under extreme loads, causing the the outside tires to deform (roll over) enough that they loose grip, or the added stress may wear out the tires to a point of failure. What all of this means is that regardless of what you do to the suspension to reduce body roll, it all 'rides' in the tires. Maybe you can see where I'm 'steering' you (wow, I'm full of puns today).

Very little roll in Cadillac ATS:



Note in the above, the Cadi's suspension is so stiff, the inside wheels are actually starting to lift off the ground! At first it might seem this would be a result of too much roll, but look at the angle of the bumper in relationship to the ground. It's near flat - almost no roll. What we are seeing is the corner being taken so hard that the suspension is compressed near max, a tremendous amount of load being transferred to the outside wheels & tires. If not for the high-performance low-profile tires, they would have folded under such stress, and the car would have slid off the tarmac. The combination of lighter weight, stiffer suspension, and better tires results in much improved lateral Gs. An un-belted passenger in this car would be pinned against the side window.

So, invest in good tires first. Your suspension depends on them. And by good I mean summer-only performance tires with firm walls and big blocks of tread near the outer edge. I think it's unwise to do anything to the suspension (for cornering performance) on our cars without upgrading the tires first. Don't worry about correcting body roll until you fix the weakest link. The stiffer you make the ride, the less work your suspension actually gets to do, and so the more important the tires become, because more demand is placed on them. And being that our Rivs are pretty heavy, that demand is huge compared to a lighter sports sedan. Find a good set of performance summer tires on sale, and install them when Spring arrives. If you can afford a larger set of wheels, you may think about lowering the tire profile with a +1 or +2 upgrade. This means your tires' side walls will be even stiffer, but it will make your ride stiffer (bumpier) as well. If you want to keep the softer ride of the Riv, stay with your 16"s and use a quality stock size tire. OEM size is less $$, too.

Good tires can be expensive, and you won't know why until you try them out. Once you have the tires out of the way, it makes more sense to modify the suspension for less body roll and stiffer ride, because the tires can support the damand. You can read here about some tires that have been tried with success: https://rivperformance.editboard.com/t38-faq-which-tires-work-best

c0reyl wrote:

Okay, so my step dad installed a brand new suspension he says is better than stock in my rivvy almost a year ago, and this car just has WAY TOO MUCH BODYROLL FOR ME, seriously.

there are tons of windy ass backroads where I live, and if I'm going down a sharp turn at like 60, my 100+ pound subwoofer gets thrashed around like a ragdoll, as well as anyone in the back seat. and the front seat to some extent. sometimes when I feel like the car is just about to lose traction, it feels like the suspension is unstable, is this my tire walls flexing, or the actual suspension? Iv'e only been driving really for a few months and have less than 10,000 miles behind the wheel, so I could be wrong blaming my suspension for feeling unsafe to corner faster. but I feel confident blaming it for bodyroll.

also, I'm interested in real heavy duty rear sway bars, which I'm thinking will help the terrible weight distribution and improve cornering, and handling. can anyone reccomend a great suspension setup for me and link me to some parts? I'd like it as stiff as possible, because I really hate this soft suspension.

PS: I want to feel safer in my car. if I have to do extreme maneuvers, it would help confidence, knowing my car can corner better. I almost died once avoiding a deer as well as another car, and ended up going offroad, going pretty fast, and ended up cracking my right rear wheel, and I think I damaged my radiator then as well, which is probably why I have to replace it now. =/


Obviously, I'm more careful and slower on the backroads now, but I really don't feel safe driving a car that if shit goes wrong, I know I can die do to limitations of the vehicle :o

in order to help I need details of what was installed.

Albertj

Sway bars will help some cars more than others due to suspension design, and the inherent geometry associated with that design. I don't know much about the late model FWD cars including the Riviera, but I do know a fair amount about The 64-72 GM A bodies. The GM A bodies are designed to understeer from the factory. Understeer is safer than oversteer, because all of the driver's reactions to severe understeer will bring the car back in line. That is not true of oversteer. Getting back to GM A body front suspension design. The A body has a camber change as the wheel/control arms move from full extension, to full compression. As the suspension compresses, the camber goes increasingly positive. The tire tilts out at the top. This results in the tire rolling over on itself, and increasing understeer. In a turn, the outside suspension goes into compression, and the inside suspension extends, as the body rolls. Putting a big sway bar on the front of a GM A body will cut down on body roll, and reduce the amount of positive camber gain. The car will understeer less as a result. Some GM cars were designed with negative camber gain. I believe the 82 and up Firebird/Camaro cars were designed this way, and of course the Corvette. With suspension compression, camber change is negative. The tire stands up straighter, and understeer is greatly reduced as the body rolls. Years ago, when I owned my first Buick, a 1972 Skylark, there was a company called HO Enterprises. They marketed a kit to use the F Body (late 70's Firebird/Camaro) spindle in the 64-72 A body front end. The kit included special taper ball joint, and F body tie rod ends. The F body spindle was a good deal taller than the stock A body spindle, and installing the kit changed the camber gain from + to -. I installed this kit on my Skylark and the transformation was absolutely amazing. I remember having to remove my rear sway bar, because the car would start to oversteer when you applied power in a turn. The front would stick like glue, and the handling was amazingly better. There were some downsides to the kit. It required a lot of alignment shims to properly align the car, and it put the upper ball joint stud at an extreme angle, but it just flat worked. Today, there are companies that make tubular control arms that solve much of the problems with the spindle swap. Much easier to do it now.

Another thing that gives a camber change is positive caster. The more positive caster you use, the more camber change you get as you turn the wheel to full lock. Mercedes Benz uses a lot of positive caster. If you've ever seen a MB parked with wheels turned full lock in one direction, you can actually see a very noticeable amount of positive camber in the inside tire. The outside tire has negative camber at full lock. Mercedes Benz cars are renowned for their handling capabilities, and this is at least one reason why.

I have no idea what suspension geometry is built into our Rivieras, but I'm sure it is different than early A bodies. The Addco sway bars helped immensely, but not as much as they did in my 70 GS. My Riviera is more fun to drive now, and there was a big improvement in transient response, and overall grip.

Riviera possesses a good amount of positive caster. +6º for the front wheels. In comparison, the C5 Corvette has +6.5º, so that might indicate our car's steering and suspension was designed with some performance initiative. According to the chief suspension engineer for the Riv, the suspension is considered "directionally strong", or without tendency to wander from a straight course. Here's a video (posted by Rivlanta) discussing some of the finer points of the chassis and suspension design:

That's great Aaron. Very interesting.

One of my favorite vids. Thanks to Craig (Rivlanta), who so far has uploaded 130 clips of Buick insider info.

nice little articl that covers a front drive as well as a rear drive sway bar set up. this should answer alot of member questions regarding swaybar selection and how to select them.



http://autospeed.com/cms/title_Sway-Bar-Shenanigans/A_2746/article.html

Stumbled upon this site and thought id share:

http://www.gmecca.com/byorc/dtipssuspension.html


Matthew

AA wrote:

Nice. You went in rear-end first, right? We want to be sure the links are doing their job.

Normally I go for the rear first, but today I went in the front  

Alignment specs: Does anybody know what caster is? Tolerance is 5.5-6.5, mine is 5.4 on the right front.

Caster is the swinging front to back of the strut at the top in the same direction as the tire rotation. When going straight it doesn't affect anything. The more you turn, the more it can put other geometry off. I don't know enough to tell you if that amount is enough to hurt anything but I'd hazard to say it's not that devastating. I don't think it's something that's generally correctable unless you have adjustable strut mount plates.

In theory,I think,the more Rearward the caster is the greater the high speed stability.The more forward the more agile at the expense of high speed tracking.

From the factory,if I recall,the caster is set at full rearward.Forward placement of the OEM settings requires you to Elongate the mounting holes.

From what I was reading, forward caster is better. Imagine it like a shopping cart wheel or a wheel on a rolly chair. When you push or pull the cart/chair the caster is pulled by the mount. Now, try pushing/pulling while keeping the mount behind the wheel. It does not work, does it?


AA maybe you would want to create a new thread for this?

matt270avian wrote:

From what I was reading, forward caster is better. Imagine it like a shopping cart wheel or a wheel on a rolly chair. When you push or pull the cart/chair the caster is pulled by the mount. Now, try pushing/pulling while keeping the mount behind the wheel. It does not work, does it?


AA maybe you would want to create a new thread for this?

..Yeah, but try pushing that 3800 pound car along the highway at a buck30,even Fred Flintstone would have a problem with that

matt270avian wrote:

Alignment specs: Does anybody know what caster is? Tolerance is 5.5-6.5, mine is 5.4 on the right front.

 
Not sure how much you "really" want to know about alignment but here you go.
 
 
These are the main angles that are "checked", or used to be years ago when I was an Automotive Service Manager. SAI and Included Angle are not adjustable, just checked. On ours, as stated before, the Caster is not adjustable unless you elongate the upper strut mounting holes so you can move it forward and backward.
 
More information here:
Wheel Alignment Explained
 
There is a lot more information at the link above, and Google search "vehicle wheel alignment explained" if you want even more information.

Thx for the reference, Randall. Also, see above posted video on the benefits of positive caster.

Sway bars, anti-sway bars, anti-roll bars, stabilizer bars. Different names for the same thing.

I've been researching sway bars a lot recently, because as soon as I think I understand them, I start thinking I really don't. It turns out there are varying opinions on the subject, so thought I'd share some of what I've learned.

It's easy to understand how sway bars work - by transferring a portion of the spring rate from the inside wheels to the outside wheels when cornering. This works to push "up" on the outside wheels, keeping the car flatter in a hard turn (reducing roll). Note: "roll" is a term used to describe the tendency of a car to lean over in a turn - not to be confused with rolling down the road, as the wheels tend to do whenever the car is moving in a straight line.

But the question always arises: why not just run stiffer springs all around? My simple answer has always been something like: the ride will be harsher all the time with stiff springs, while stiffer sway bars will only feel harsh during a hard corner. That's somewhat true, but there's more to it than that.

Yesterday I found a thread on Corvette forums that asks this very same question, and the answers given there were pretty enlightening. The thread link is listed below, but I will summarize what I found most relevant.

Basically, stiffer springs can absolutely replace sway bars to correct body roll. In theory, if a sway bar on either axle transfers x amount of spring rate from the inside to the outside, it can at most be double the rate of one spring, so if you double the spring rates of both wheels, the car will have a similar amount of roll correction. But... if you add a sway bar to already stiffer springs, you can now double the spring rate of the stiffer springs! So no matter how stiff the springs are, adding a sway bar always makes the outside wheels stiffer - when in a turn.

So what happens when the car is moving but isn't cornering? Well, the springs just support the car, and the sway bars don't do a whole lot. The bars just move with the control arms, as the wheels roll over bumps. It's really just the springs and struts doing all the work to keep the car level, and from bouncing around too much.

Speaking of struts, what effect do they have on body roll? Struts don't prevent body roll, but they can delay it. Different struts delay compression of the outside wheels by different amounts of time, depending on how firm they are. I found that pretty interesting.

Knowing all of this, we can say a firmer strut, a stiffer spring, and a bigger sway bar all work together to prevent body roll, although they do so in like and different ways. But so far we've only talked about body roll in the corners. There are two other motions the car makes every time it's driven: squat and dive.

Squat and dive are unique in that they are only attenuated by the struts and springs. Once again, struts can only delay squat or dive, while springs work to limit the amount. Other factors, such as wheelbase and center of mass, also come into play here. Sway bars have zero effect on squat and dive, and now we can begin to answer the age old question - springs or sway bars?

If we consider springs and struts are the only way to control squat and dive, then we must modify these areas for the needed control! If the nose dives under braking, or the rear squats under acceleration, stiffer springs and/or firmer struts can address this. If the car's squat and dive characteristics are acceptable, springs or shocks may not need upgraded.

What acceptable for squat & dive? That's a whole other book, but basically if the car squats too much, it won't get good traction off the line or out of a corner. If it dives too much, the car will more easily lose control when braking hard in a corner (similar to lift-off oversteer). It is possible for the car to be oversprung, too, in which case it will not be able to brake as effectively, or apply as much power to the ground.

Once squat and dive are deemed acceptable, it's time to focus on roll. If there is still significant roll in the corners after springs and struts have been upgraded, stiffer sway bars are probably the next step. High density bushings and links can make the action of the sway bars even more effective at their jobs, if needed.

One final point: where you drive and how you drive could determine whether you need to focus more on addressing squat & dive or body roll. For example, on public roads and on some autocross courses, the road surface can be bumpy. A lower spring rate can help the tires grip the surface in the corners. Sway bars can help in autocross with quicker left-to-right transitions, like in a slalom. A road course track tends to be smoother and can support a higher spring rate, with less need for sway bars since the left-to-right load shifts usually occur more slowly.

That's all I got for now. Hope this info helps somebody out. This does have me wanting a set of firmer springs on my car, and it also seems to confirm that putting a stiff rear sway bar on an already front-heavy car with soft springs might not be the best idea. To be safe, install stiffer springs and firmer struts first. Or just use stiffer sways front and rear - I went this route and can still get the back end to come out when I try.

Link: http://forums.corvetteforum.com/autocrossing-and-roadracing/2777413-stiffer-springs-vs-larger-swaybars.html

Great info AA! What do you know about body flex and how that affect body roll?

RidzRiv wrote:

Great info AA! What do you know about body flex and how that affect body roll?

Body flex is always bad. If the car flexes the suspension guy has to work with the flex.Since flex is unpredictable it's impossible to tune to IT.The chassis has to be stiff enough to allow the suspension,swaybars,to be at their peak.

Crazy question. If I were to put 2 spare tires on the rear while keeping stock in the front would it improve handling on an autocross course? The logic behind it is that it will help the rear end rotate with minimal effort, reducing understeer.

You're correct that putting narrower tires in rear would cause the car oversteer, but the flaw in this approach is the overall contact patch is decreased; so is overall grip. In other words, your tires will exceed max road friction, lessening lat-G in the corner. There are better ways to address FWD understeer, like weight distribution, sway bars, and springs. If you want to change tires, widen the fronts. This will also reduce torque steer under acceleration (aka '05 GXP).

What an awesome video. Check it out if you haven't riv
fans

AA wrote:

Riviera possesses a good amount of positive caster. +6º for the front wheels. In comparison, the C5 Corvette has +6.5º, so that might indicate our car's steering and suspension was designed with some performance initiative. According to the chief suspension engineer for the Riv, the suspension is considered "directionally strong", or without tendency to wander from a straight course. Here's a video (posted by Rivlanta) discussing some of the finer points of the chassis and suspension design:

I like to buy as many upgrade parts at the salvage yard as possible to save money.  Are there any cars that have larger anti-sway bars that fit our Rivieras?  Such as Bonnevilles, etc?