Camber Gain

[racerjoe]

Can someone educate me on exactly what camber gain is and how to improve it? I've read some articles online and I must be having a mental block. If one was to use the extended upper ball joint to help with camber gain, what is it actually doing?
Does it help when the suspension is compressed or extended? (inside tire on a turn or outside)
Still pictures hardly ever do much justice of how hard my car is turning since it stays relatively flat thanks to the large t-bars and Hotchkiss sway bar. You can tell by the rear tires, this is a relatively hard turn. The outside (driver) front tire appears to be planted pretty good, while the inside has some negative camber is is taking the outside edge of the tire off the ground.
Would the extended ball joints help this?
I have a static -1.5 camber and 5.5 caster, but I don't think any of that really pertains to camber gain.

Now that I'm starting to learn the car and how it reacts on the autocross, I can make it understeer in a hard 90 degree turn. I don't currently run a rear sway bar, but I think I need to add one to help reduce the understeer. Correct me if I'm wrong.

Help me understand suspension gurus!

 

[AJ/FormS]

I think that's easy for me to understand. If I understand your question rightly (that's another story,lol), here goes;
Our Mopar front suspensions have un-equal-length control arms. When the suspension goes up relative to the body, this design forces the wheel to tilt inwards at the top. The higher it goes the more it tilts in.
As the suspension droops from it's static ride height, the top of the tire gets tilted inwards again.
Somewhere in the middle, your alignment tech can set the camber to zero, and the factory design is such that at the specified ride height, the camber change is supposed to remain relatively small in about the first inch of suspension travel, in either direction.
This camber change cannot be eliminated with the factory design.
This design is for two reasons; 1) in a straightline, it attempts to keep the tire relatively flat to the road as the suspension moves up and down, in that ~2" window. and 2) in a turn, the wheel with the load on it moves up into the wheelhouse, thus tilting the top of the wheel inboard; while simultaneously the other side of the car rises up and tilts the wheel back towards straight up. Thus the cornering force is sent to a tire that is nearly flat to the road, and this gives the tire the best chance to NOT slip sideways.

Your factory alignment specs to a really good job at this, and the proof is in the long tire life.
The thing is, when you increase caster beyond the factory amount, this destroys your camber "neutrality". This action, causes the steering geometry to be changed, and at zero-toe, the tire-tilt changes speed and amount. If you don't do something about it, the car will self-steer when it encounters a change in ride-height, such as a bump or dip or during turning. And also when the edges of the tires come against a change in the road flatness like ruts; the tires will try to climb up the side of the rut, and you will interpret this at the steering wheel as "nervousness" or perhaps "wandering". This is called bump-steer. On a street car, bump-steer is IMO, unacceptable.
This cannot be eliminated. But it can be minimized by restoring the camber curve to get the window back. Most of this bump-steer is caused by the steering knuckle-arms having been tilted downwards, relative to the pitman/idler arms. So you have to restore that angle. But another portion of the bump-steer was caused by the combination of caster-plus-camber change, which caused the knuckle arms to move outboard relative to the centerline of the car. So you gotta fix that as well.
All of this is best done in the alignment shop, because it will require plotting the camber curves multiple times. The proper way to minimize this is to BEND the knuckle arms up and inboard. But if you have never done this before, you have no idea how far to bend them. So after each attempt, you have to produce another graph.
You have to start in the window of minimum camber change.
The second best way is to shim the tierods up and make another graph. Then shim the knuckle arms over, and take another graph. As often as may be required to get the camber change minimized in the 2inch window of suspension change.
If you find the ride height unacceptable when you are done, you will have to change it by tire diameter. As for me, I just lowered the rear until I liked it.

 

[67Dart273]

------------And especially for Mopars with easily adjustable suspension height, "non" standard suspension positioning can aggravate or at least change the problem-----------

 

[70 Buster 340]

Google - Bump Steer

 

[RustyRatRod]

I've never seen an "extended" ball joint for a Mopar. I've seen the offset control arm bushings.

 

[racerjoe]

I think that's easy for me to understand;
Our Mopar front suspensions have un-equal-length control arms. When the suspension goes up relative to the body, this design forces the wheel to tilt inwards at the top. The higher it goes the more it tilts in.
As the suspension droops from it's static ride height, the top of the tire gets tilted inwards again.
Somewhere in the middle, your alignment tech can set the camber to zero, and the factory design is such that at the specified ride height, the camber change is supposed to remain relatively small in about the first inch of suspension travel, in either direction.
This camber change cannot be eliminated with the factory design.
This design is for two reasons; 1) in a straightline, it attempts to keep the tire relatively flat to the road as the suspension moves up and down, in that ~2" window. and 2) in a turn, the wheel with the load on it moves up into the wheelhouse, thus tilting the top of the wheel inboard; while simultaneously the other side of the car rises up and tilts the wheel back towards straight up. Thus the cornering force is sent to a tire that is nearly flat to the road, and this gives the tire the best chance to NOT slip sideways.

Your factory alignment specs to a really good job at this, and the proof is in the long tire life.

I'm autocrossing the car. I care more about better handling than tire wear. My question is focused on performance handling with larger wheels/tires vs. a stock suspension with small tires.

 

[racerjoe]

I've never seen an "extended" ball joint for a Mopar. I've seen the offset control arm bushings.

SPC is making a new upper control arm that has an extended ball joint to help with camber gain. I'd like to understand where it is "helping".

 

[TT5.9mag]

@racerjoe look up “the Shelby mod” for Ford vehicles. Although the suspension design is different, you’ll find a good explanation of what camber gain is and how to change it for the better with regards to making the car handle.

 

[1WildRT]

SPC is making a new upper control arm that has an extended ball joint to help with camber gain. I'd like to understand where it is "helping".

Since the lower arm is sprung changing the effective spindle height doesn't change the LCA's position, instead it raises the outboard end of the upper control arm bringing it closer to the point where camber change begins to occur before the cornering load is applied...

A set of FMJ spindles drop right in and are 1" taller accomplishing the same thing...

 

[TT5.9mag]

Understanding Shelby/Arning Drop Changes
A good explanation

 

[autoxcuda]

Google - Bump Steer

No - different concept

Bump steer is a separate suspension geometry concept. It’s designed for and measured differently than Camber Gain.

It’s still important though.

 

[autoxcuda]

I've never seen an "extended" ball joint for a Mopar. I've seen the offset control arm bushings.

You’re not looking out of the box enough. Understandable, you’re probably not that into it.

The large upper control arm ball joint, K727, is the preferred upper ball joint on most circle track cars.

Howe was the first to offer rebuildable and adjustable K727 style ball joints. The adjustable part was you can set the tightness (lash) between the ball and cup.

Now think of them as modular ball joints. Well they offer different height pins that like 1wildrt described effectively raise the upper spindle pivot point.

examples:

Howe:

QA1

Speedway Motors:

 

[autoxcuda]

These are the different pins heights
you can install.

 

[TT5.9mag]

No - different concept

Bump steer is a separate suspension geometry concept. It’s designed for and measured differently than Camber Gain.

It’s still important though.

While it is a different and separate geometry issue in front suspensions, the concept is remarkably similar. Different length parts, mounted at different points causing those parts to move in different arcs. But you knew that.

 

[70 Buster 340]

When I 'bumped' my oval track cars we measured Caster, Camber, Ackerman and Dive changes through the range of travel.

 

[autoxcuda]

I think that's easy for me to understand. If I understand your question rightly (that's another story,lol), here goes;
Our Mopar front suspensions have un-equal-length control arms. When the suspension goes up relative to the body, this design forces the wheel to tilt inwards at the top. The higher it goes the more it tilts in.
As the suspension droops from it's static ride height, the top of the tire gets tilted inwards again.
Somewhere in the middle, your alignment tech can set the camber to zero, and the factory design is such that at the specified ride height, the camber change is supposed to remain relatively small in about the first inch of suspension travel, in either direction.
This camber change cannot be eliminated with the factory design.
This design is for two reasons; 1) in a straightline, it attempts to keep the tire relatively flat to the road as the suspension moves up and down, in that ~2" window. and 2) in a turn, the wheel with the load on it moves up into the wheelhouse, thus tilting the top of the wheel inboard; while simultaneously the other side of the car rises up and tilts the wheel back towards straight up. Thus the cornering force is sent to a tire that is nearly flat to the road, and this gives the tire the best chance to NOT slip sideways.

Your factory alignment specs to a really good job at this, and the proof is in the long tire life.
The thing is, when you increase caster beyond the factory amount, this destroys your camber "neutrality". This action, causes the steering geometry to be changed, and at zero-toe, the tire-tilt changes speed and amount. If you don't do something about it, the car will self-steer when it encounters a change in ride-height, such as a bump or dip or during turning. And also when the edges of the tires come against a change in the road flatness like ruts; the tires will try to climb up the side of the rut, and you will interpret this at the steering wheel as "nervousness" or perhaps "wandering". This is called bump-steer. On a street car, bump-steer is IMO, unacceptable.
This cannot be eliminated. But it can be minimized by restoring the camber curve to get the window back. Most of this bump-steer is caused by the steering knuckle-arms having been tilted downwards, relative to the pitman/idler arms. So you have to restore that angle. But another portion of the bump-steer was caused by the combination of caster-plus-camber change, which caused the knuckle arms to move outboard relative to the centerline of the car. So you gotta fix that as well.
All of this is best done in the alignment shop, because it will require plotting the camber curves multiple times. The proper way to minimize this is to BEND the knuckle arms up and inboard. But if you have never done this before, you have no idea how far to bend them. So after each attempt, you have to produce another graph.
You have to start in the window of minimum camber change.
The second best way is to shim the tierods up and make another graph. Then shim the knuckle arms over, and take another graph. As often as may be required to get the camber change minimized in the 2inch window of suspension change.
If you find the ride height unacceptable when you are done, you will have to change it by tire diameter. As for me, I just lowered the rear until I liked it.

Just cause you increase caster, does not automatically mean you have bad bump steer enough to cause a noticeable driving condition change like “nervousness or wandering” That’s a too absolute view of it.

My car is extremely lowered. And it’s got 4 degrees of positive caster and 1 degree negative camber.

I have a bump steer gauge and I’ve measured it. It’s not bad at all. Especially for typical street car.

Just an FYI, 0.082" is only a little over 1/16" toe out at 3" compression. And 0.114" is only a little under 1/8" toe in at 3" rebound/extension.

and for compression when it hits a bump or rolls into a corner that is

A typical rut in the highway or a pavement separation will not compress the suspension 3”. Maybe an 1”

 

[autoxcuda]

While it is a different and separate geometry issue in front suspensions, the concept is remarkably similar. Different length parts, mounted at different points causing those parts to move in different arcs. But you knew that.

Yes that’s suspension geometry as a whole.

concepts-issue-phenomena…. different terms of description

maybe it’s better defined as a chassis tuning item. That what the Milliken book calls it:

 

[autoxcuda]

Back to the Original Poster’s question about Camber Gain…

I just found this nice explanation at Bob Wright - The Science of Setup

The concepts are the same no matter size of vehicle

 

[racerjoe]

Since the lower arm is sprung changing the effective spindle height doesn't change the LCA's position, instead it raises the outboard end of the upper control arm bringing it closer to the point where camber change begins to occur before the cornering load is applied...

A set of FMJ spindles drop right in and are 1" taller accomplishing the same thing...

I have the FMJ spindles already.

 

[TT5.9mag]

There is a delicate balance between too much and too little camber gain because of the effects during different vehicle situations. What makes the car turn in and corner well, will end up hurting braking performance.

 

[racerjoe]

Back to the Original Poster’s question about Camber Gain…

I just found this nice explanation at Bob Wright - The Science of Setup

The concepts are the same no matter size of vehicle

View attachment 1715838122

Thanks for all this information. I’ll read through it to digest it all. I was hoping you (and a few others) would chime in. Do you think there is a benefit to the taller ball joint?

 

[TT5.9mag]

There can be a benefit to the longer ball joint stud. Usually stock suspension geometry is designed to keep grandma from driving in to a ditch. Manufacturers have to keep the vehicle predictable and they set them up to react to the natural tendencies of “most” drivers. For instance, the natural reaction to understeer is to lift off the gas, which loads the front end and plants the tires. They can set up the car to be predictable and less likely to go out of control during these situations which may not be (and in most cases isn’t) the best for handling. Setting up your particular car for your driving style and usage (auto cross will be different from open road racing) will be a trial and error type of thing. So the blanket statement of “the longer ball joint stud being better” is subjective.

 

[Treblig]

I used the "adjustable" SPC upper control arms on my '69 Barracuda. They have endless adjustment on them. The alignment guy who had 25 years experience with older cars said that they made his job easy.

 

[TT5.9mag]

I used the "adjustable" SPC upper control arms on my '69 Barracuda. They have endless adjustment on them. The alignment guy who had 25 years experience with older cars said that they made his job easy.

While the SPC uppers are nice and do have a lot of adjustment, setting static camber and changing the geometry for more/less camber gain are two completely different things. Although the overall length of the arm can be changed and that does have a slight effect.

 

[RustyRatRod]

SPC is making a new upper control arm that has an extended ball joint to help with camber gain. I'd like to understand where it is "helping".

Ok, so the control arm is extended, not the ball joint. IMO, these cars don't need camber help near as often as they need help with more caster. I've never seen one that I've ever had problems getting enough camber out of.