Front end suspension geometry

T

Turbosbc

Not-quite-so-new-guy
Aug 3, 2018
10
10
3
Kangasala, Finland
#1
My first question here....

I'm planning to upgrade my malibu's ability to make through corners. I will be using tall balljoints and tubular upper control arms. Is it better to use Drop springs or drop spindles? Which one gives me better geometry? I plan on using moog springs about 600-700 range.
 
fleming442

fleming442

Comic Book Super Hero
Dec 26, 2013
3,379
1,513
113
#2
I'm going to say drop spindles. Of course, it all depends on how you use the car. Mine's a DD with drop Blazer spindles and Moog 5662 springs which are almost as stiff as you can get. To me, it handles pretty darned good and rides about the same. Aesthetically, I want it lower, however, I'm trading off for ride quality. Depending on tire size and height, you will bottom out in the top of the wheel well. Click the link in the sig for pics.
 
superbon54

superbon54

Greasemonkey
Apr 15, 2014
107
157
43
#3
“Is it better to use drop springs or drop spindles?”

Depends.

Ideally the lower control arms will be parallel with the ground. On g bodies this can be achieved with 1-2” drop springs, and is dependent on many factors such as spring free height, rate and weight over the front wheels. Each car is different.

Any drop beyond that should be done with spindles. Too much drop on springs puts the car on bump stops in jounce, and too much drop on the spindle can create wheel interference.

You’re on the right track with the taller upper BJ. A level LCA with an upper LCA that is angled slightly upward toward the spindle fixes a lot of the positive camber issue that makes g bodies handle like a la-z-boy compared to modern cars.

I wouldn’t use any more spring rate than you need if you’re looking for a street car with moderate drop that handles. With the geometry mods, 550-650 is probably more than good depending on your engine. Just be sure to run a big enough sway bar.
 
Streetbu

Streetbu

G-Body Guru
May 22, 2011
570
615
93
Central NY
#4
Front lower control arm parallel to the ground, you won't need drop springs if you get that to happen. Don't drop it too far or your tires WILL rub the inner fender constantly. Ask me how I know.
 
T

Turbosbc

Not-quite-so-new-guy
Aug 3, 2018
10
10
3
Kangasala, Finland
#5
Thanks for the information. I ordered moog 5660 springs, catalog says rate 639 lb/in. I guess i swap lower balljoints (tall), springs and 5.3 engine and see how the ride height looks.
 
pontiacgp

pontiacgp

Canadian Prime Minister
Mar 31, 2006
22,871
3,832
113
Kitchener, Ontario
#6
Thanks for the information. I ordered moog 5660 springs, catalog says rate 639 lb/in. I guess i swap lower balljoints (tall), springs and 5.3 engine and see how the ride height looks.
if you don't like the ride height with the 5660 springs for every 1/4 coil cut that will drop the car 1"
 
MC96

MC96

Greasemonkey
Dec 7, 2015
222
89
28
#7
Dont put too much stock in having the lowers parallel. But it is a tried and true method. Work on things like bump steer and general steering geometry.

(Kinda like "people buy horsepower, but people drive torque")

Bump steer kits can be bought through UMI or pieced out through a combo of UB machine or speedway parts and Allstar parts.

Adjustable centerlinks help too but are pricy. A 3rd gen camaro one has been offered for years by afco with the price about quadrupled, sold as a "bump steer correcting" centerlink

Im wondering when someone is going to wise up and take the 3 piece speedway spindle and build an adapter for that to go right to huge brakes. An adjustable steering arm would go on it without much change.
 
Last edited:
pontiacgp

pontiacgp

Canadian Prime Minister
Mar 31, 2006
22,871
3,832
113
Kitchener, Ontario
#8
to deal with bump steer I have my tie rod sleeve parallel to the lower control arm
 
Macguyver

Macguyver

SOUTHSIDE MACHINE PERFORMANCE
GBodyForum Sponsor
Mar 21, 2017
44
39
18
#9
Why Modified Front End Geometry is Needed

If you want to improve the handling of your ride, you must first understand what is wrong with the original geometry. From the factory, these cars were designed to understeer. To make them do this, they used a very short spindle with the upper A-arm at a steep downward angle, which results in a backward camber curve making the tires lean out of a turn, using only the edges of the tire. Not only is this bad for mechanical grip, it's also why every stock G Body wears the outside edges of the front tires. Below is a diagram of the stock geometry at rest, and then in a hard turn. Notice the severe angle of the tires. All of the cornering forces are placed on a very small area of the tire.


To deal with this problem, there are several things that will help. Simply lowering the car will help to some extent, but not nearly enough to correct the whole problem. Bigger sway-bars will reduce the amount of bad camber gain, but again, it's not enough... it's like a band-aid on a gunshot wound.
To fix the bad geometry, you need a taller effective spindle height. The "effective height" of a spindle is from the pivot center of the upper balljoint to the pivot center of the lower balljoint. Tall spindles with stock balljoints, or stock spindles with extended balljoint studs will both achieve this goal.
Below is a diagram of the same car equipped with a taller effective spindle height. Notice that the tires remain near vertical using the entire tread evenly across its contact patch. This is key to getting the most grip, and life out of your tires.




The SSM Stage 1

The secret is the combination of the extra tall ball joint to match your new tubular upper arms which greatly improves the camber curves and relocates the roll center. This means more grip and less body lean. The 1" EXTRA tall upper ball joints reverse the backward factory camber curves for a huge increase in grip. They also raise the extremely low factory roll center to dramatically reduce body roll
For stock and lifted cars this radically corrects poor ball joint angle and helps the arm clear the frame when lifted properly.




The SSM Stage 2
The stage 2 goes even a step beyond the Stage 1 Plus and further corrects the terrible backward geometry of the factory front suspension, by using Racing Series ball joints.
They are much stronger, smoother, and longer lasting, than original GM, or any other aftermarket ball joint.The .5" taller lower ball joints further improve the camber curves and roll center location, significantly reducing lateral roll center migration for more predictable behavior.
They also correct the factory bump steer issues by raising the tie rod ends into proper alignment.Now with extremely improved geometry designed for the rigors of SCCA, TransAm and NASCAR your car will truly dominate the street and track!

The low-friction ball joints are legal for classes that require non take apart joints or OE style joints. Additionally, all low-friction ball joints have 32 degrees of swing angle for maximum suspension travel and contain no springs or plastic parts. Dust boots are not included but available at your local auto parts store. Dust boots can retain dirt and also hinder visual inspections.



Changing just the upper A arms can only do so much. The length and offset of the arms has very little effect on camber change, roll center or overall handling. They add + caster which can make the car track straighter at speed and improve turn in. However too much can make the car feel vague and the steering sluggish so that only goes so far. As the + caster is increased there is a tiny improvement in camber as a side effect when the wheels are turned. Our upper arms have this benefit as well as more caster adjustment. To make any profound improvement in the suspension geometry of cars that need it the actual pivoting points (pickup points) that determine that geometry need to be moved vertically. Road race cars like SCCA, TransAm, LaMans Series race cars and fast DRAG CARS use special taller spindles, raising the upper ball joint pivot points like our Stage 1 and 2 packages do. This was the genesis of our AFX tall spindles for the GM A Body platform cars. For years circle track racers that run stock G or F body chassis have used taller truck upper ball joints, which seated improperly to improve the geometry. They’ve been doing this kind of thing for years by fabricating new parts, mixing and matching stock parts, modifying suspension/frame mounts etc. That’s how to win races with a less than perfect factory chassis and a small budget. We’ve taken that race experience, applies new technology and brought it up to date with our SSM STAGE 2 package. Major suspension improvements, not just shiny parts.
They'll physically bolt together and you could drive the car around but there's a catch or two. There's the fact that the original arms on G body cars were originally designed to droop down over the frame and have the ball joints at the proper angle for a full range of travel. Once you lower the car, go to taller spindles or ball joints etc. the arms end up closer to level and the ball joints end up close to binding at ride height. Hitting a big bump can bind up the ball joints and put a tremendous amount of stress on them as well as the upper A arms and A arm mounting bolts. They'll only take that for so long before something fails...
Much of it also has to do with alignment. A lot of folks think if their car goes straight and doesn't chew up the tires that it's aligned properly and working as well as it can. They're kidding themselves and they're missing out on a LOT of performance. The alignment specs recommended in the `60s and `70s (and even `80s!) were anything but performance oriented. In fact they've changed little since the 1940s. Today almost every car is using power steering and we're all running high performance radial tires (except for the resto guys but that's another story...) these tires are often more than twice the width of the originals, we've also got another 40 years or so of experience to draw on. What's more, once we've corrected the geometry so that it works like a new performance car it demands the same type of alignment those cars run to achieve peak performance.
Modern performance cars run a LOT more + caster and - camber. The + caster helps the cars track better at highway speeds and gives better steering feel. The - camber helps keep the tire's contact patch flat on the road surface during cornering. It's part of what makes new cars drive like new cars. Using these kinds of settings on older cars yields a BIG improvement in drivability and performance but because they were designed around different specs it's usually impossible to attain the best numbers with stock parts and shims. Lowering the car or increasing the effective spindle height with taller spindles or taller ball joints all add more + camber making it ever harder to dial in a - camber setting (which is what we want). That's the big reason for different upper arms. The taller spindles or tall ball joints make the big geometry improvements and the proper upper A arms make it possible to combine the new parts and geometry with the proper performance alignment, an unbeatable combination!​



 

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