S550 Suspension School - Integral Link IRS

[Whiskey11]

No, Virtual Pivot uses a double wishbone.

No, Caster will not be adjustable. That needs to be done during R&D.

I don't know of any way to say this but you are wrong... the name Virtual Pivot Suspension in Ford's design language is not specific to the dual wishbone setup, the concept is applied to strut suspensions as well as the name Virtual Pivot has to do with the dual ball joints projecting a virtual pivot point that is not a physical point in the suspension but is in "space" just outboard of the actual suspension components.

You can definitely adjust caster by tweaking the tension link's length, and toe, and camber... Or you can cant the top of the strut rearward, something which will have to be done in the aftermarket. I suspect Ford is going to be shipping these cars with a healthy +7.0º or more caster and once you have the ability to adjust it (through the aftermarket or if Ford has adjustment for it factory) it doesn't help to add more caster to the suspension so long as it does not compromise the ability to achieve the static negative camber you need.

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[thePill]

I don't know of any way to say this but you are wrong... the name Virtual Pivot Suspension in Ford's design language is not specific to the dual wishbone setup, the concept is applied to strut suspensions as well as the name Virtual Pivot has to do with the dual ball joints projecting a virtual pivot point that is not a physical point in the suspension but is in "space" just outboard of the actual suspension components.

Sorry, once the strut becomes the upper control arm, it become a MacP system. In order to be a Virtual Pivot, it must use an upper and lower control arm. Virtual Pivot gets its name from the bicycle system and was designed to be an alternative to Short/Long Arm. The DB MacP system was design to mimic the VP system but it is NOT a Virtual Pivot.

I believe some of my bad info on this initially was confusion about the systems.
An upper wishbone is needed, other systems are either Short-Long Arm based or MacP based.

I will need to see at least one system that uses a MacP system that uses an upper wishbone or A to agree with you here. The actual "Virtual Pivot" is responsible for pivoting the upper control are (wishbone).

You can definitely adjust caster by tweaking the tension link's length, and toe, and camber... Or you can cant the top of the strut rearward, something which will have to be done in the aftermarket. I suspect Ford is going to be shipping these cars with a healthy +7.0º or more caster and once you have the ability to adjust it (through the aftermarket or if Ford has adjustment for it factory) it doesn't help to add more caster to the suspension so long as it does not compromise the ability to achieve the static negative camber you need.

I think you have caster confused with something else.

Since this is a MacP system, the actual adjustment would have to be at the strut tower. Caster is usually something that isn't adjusted unless the vehicle was in a collision. Once Ford sets the caster, it cannot/should not be tampered with. Toe and Camber are a different story.

I appreciate your help Whiskey but, we need to make sure the data here is as close to accurate as possible. If there is some new info I am not aware of, I am eager to hear it.


VP is a version of Double Wishbone, DB is a MacP design. The Tension and Lateral Links will not adjust the caster of the front suspension. That adjustment is not advised... However, if you needed an alignment done, the strut tower on a MacP system is where you would make that adjustment.

 

[Whiskey11]

Sorry, once the strut becomes the upper control arm, it become a MacP system. In order to be a Virtual Pivot, it must use an upper and lower control arm. Virtual Pivot gets its name from the bicycle system and was designed to be an alternative to Short/Long Arm. The DB MacP system was design to mimic the VP system but it is NOT a Virtual Pivot.

I believe some of my bad info on this initially was confusion about the systems.
An upper wishbone is needed, other systems are either Short-Long Arm based or MacP based.

I will need to see at least one system that uses a MacP system that uses an upper wishbone or A to agree with you here. The actual "Virtual Pivot" is responsible for pivoting the upper control are (wishbone).

I think you have caster confused with something else.

Since this is a MacP system, the actual adjustment would have to be at the strut tower. Caster is usually something that isn't adjusted unless the vehicle was in a collision. Once Ford sets the caster, it cannot/should not be tampered with. Toe and Camber are a different story.

I appreciate your help Whiskey but, we need to make sure the data here is as close to accurate as possible. If there is some new info I am not aware of, I am eager to hear it.


VP is a version of Double Wishbone, DB is a MacP design. The Tension and Lateral Links will not adjust the caster of the front suspension. That adjustment is not advised... However, if you needed an alignment done, the strut tower on a MacP system is where you would make that adjustment.

A strut based setup with dual lower ball joints will still create a virtual pivot point for the front suspension no matter how you want to argue the semantics, it is a Virtual Pivot setup. There is no mimicking, it IS. In an SLA setup such as what you are claiming is the "only" virtual pivot setup you look at the top down and draw the lines through the suspension links to determine where the suspension is pivoting from. This is no different on the S550's strut based, virtual pivot suspension. In a standard strut setup, the lower ball joint acts as the lower "pivot point" and the upper strut bearing plate the upper pivot point. The steering axis inclination in front view will be the line drawn through the ball on the ball joint and through the upper bearing plate.

On a dual ball joint setup it gets slightly more complicated as the lower pivot point is NOT the ball joint for the lateral link OR the tension link, it's the line drawn through both ball joints intersection point which changes the steering axis inclination.



See the change in steering axis inclination? That is due to the VIRTUAL PIVOT created by the two lower links with two ball joints. That has a profound impact on the way the front suspension behaves and it DOES NOT have to be a SLA setup to have a virtual pivot point.

As for the caster angle, the caster angle works in the same fashion as the steering axis inclination (infact, SAI in side view is the caster angle) just in side view instead of front view. If you tilt the top of the strut rearward, even slightly, it will make a change in the caster angle -OR- you can move the lower pivot point, virtual or otherwise, forward or rearward to change caster angle. Ford sold through the dealership, a packaged pair of camber bolts AND caster bolts. The CASTER bolts were put in the rear lower control arm mounting point and it's "cam" lobe would adjust the angle of the front lower control arm to move it forward/aft to change caster.

You can do the same thing with a dual ball joint (or Virtual Pivot as I like to call a spade a spade) setup by changing how fore/aft the virtual pivot point is. The easiest way to do this is to move the lateral link's chassis mounting point forward or aft on the chassis.

There are dozens of advantages to increasing the caster angle on the suspension, the primary benefit might a lesser need for static negative camber as caster turns to camber as the wheel is turned. That can impact tire wear on the straights on a road course. To give you an idea of what I mean, lets look at an SLA setup from the 1960's with relatively low caster:



The solution is to either run more caster (hard to do) or more static negative camber:

That's -6.0º of camber due to a distinct LACK of Caster. Of course, once you get above +7.0º the need for more is obviously less. However it still works in a similar manner, more caster can reduce the need for large amounts of negative camber when the car is static.

 

[qwkcoupe]

Caster folks,

I can help with that. It is not complicated. Recall A^2 + B^2 = C^2

s550 Front Caster absolutely can be adjusted by aftermarket generic parts in the lower arms which will increase wheel base, and optionally the track width, within tire rub constraints. The s550's separate Lateral and Tension links, once customized, should be a whole lot easier than the old days of mid-80's SVO lower control arms, or otherwise aftermarket A-arms.

1. Shorten the Tension Link to bring the axle center line forward to increase caster with a detriment to camber and track width
2. Lengthen the Lateral Link to increase caster and reintroduce camber and track width.
3. Optionally, Increase the distance between the spindle and bottom strut mount ONLY if you want to reintroduce stock ride height.

Thankfully those links are rather straight, so we can go rummage through the generic race parts catalog to find suitable adjustable replacements.

As with all things, you have to a have good reason before changing Ford's design. I see a whole lot less reaons with this generation....

Hope that helps :ford:

 

[Whiskey11]

Caster folks,

I can help with that. It is not complicated. Recall A^2 + B^2 = C^2

s550 Front Caster absolutely can be adjusted by aftermarket generic parts in the lower arms which will increase wheel base, and optionally the track width, within tire rub constraints. The s550's separate Lateral and Tension links, once customized, should be a whole lot easier than the old days of mid-80's SVO lower control arms, or otherwise aftermarket A-arms.

1. Shorten the Tension Link to bring the axle center line forward to increase caster with a detriment to camber and track width
2. Lengthen the Lateral Link to increase caster and reintroduce camber and track width.
3. Optionally, Increase the distance between the spindle and bottom strut mount ONLY if you want to reintroduce stock ride height.

Thankfully those links are rather straight, so we can go rummage through the generic race parts catalog to find suitable adjustable replacements.

As with all things, you have to a have good reason before changing Ford's design. I see a whole lot less reaons with this generation....

Hope that helps :ford:

Thank you!

 

[qwkcoupe]

Thank you!

Your welcome.

 

[thePill]

You guys are more than welcome to fabricate your links, I am just saying, and still say this... Don't adjust your caster. I don't think the regular toe and camber adjustments will alter the caster. It may change the center of the contact patch but, that's about as much caster as I would want to mess with.

 

[thePill]

You guys are too advanced here in thought and experience. As gwkcoupe says above, he sees less reason to alter the caster this generation.

OEM up to Pro-Am, caster will not be touched.

 

[Whiskey11]

You guys are more than welcome to fabricate your links, I am just saying, and still say this... Don't adjust your caster. I don't think the regular toe and camber adjustments will alter the caster. It may change the center of the contact patch but, that's about as much caster as I would want to mess with.

:frusty:

What is going to happen if I adjust my caster, is my car going to explode? No, it wont, nor will it negatively impact the way my car handles or rides...

I'd love to hear your reasoning as to why I shouldn't alter my caster setting.

 

[thePill]

:frusty:

What is going to happen if I adjust my caster, is my car going to explode? No, it wont, nor will it negatively impact the way my car handles or rides...

I'd love to hear your reasoning as to why I shouldn't alter my caster setting.

I'm not saying you shouldn't, I'm just saying the '15's DB MacP doesn't have that adjust-ability built into it. You need to fabricate the links to do that.

I can think of a few classes that may allow for me to alter my wheelbase but, most that come to mind are very advanced.

As I said initially,

Our two major adjustments on any independent suspension is "Toe" and "Camber"... "Castor" is not to be played with. In order to translate suspension, you need to understand the wheel movement associated with both "Toe" and "Camber"

The two major adjustments are toe and camber. I tried to associate those two adjustments with the new systems Tension and Lat links so people could better understand the new suspension. I didn't want to get into custom fabrication and changing caster...

 

[Whiskey11]

I'm not saying you shouldn't, I'm just saying the '15's DB MacP doesn't have that adjust-ability built into it. You need to fabricate the links to do that.

I can think of a few classes that may allow for me to alter my wheelbase but, most that come to mind are very advanced.

As I said initially, The two major adjustments are toe and camber. I tried to associate those two adjustments with the new systems Tension and Lat links so people could better understand the new suspension. I didn't want to get into custom fabrication and changing caster...

That's definitely not what you said, you said Caster should not be played with, as if messing with it will doom your car to dump truck handling capability.

As for changing wheel base, even Street Touring and Street Prepared in SCCA Autocross you can change the lower control arms in a strut based suspension... it does condemn you to not having caster/camber plates though so the advantages would have to out weigh the disadvantages.

 

[thePill]

That's definitely not what you said, you said Caster should not be played with, as if messing with it will doom your car to dump truck handling capability.

As for changing wheel base, even Street Touring and Street Prepared in SCCA Autocross you can change the lower control arms in a strut based suspension... it does condemn you to not having caster/camber plates though so the advantages would have to out weigh the disadvantages.

It isn't to be played with, especially if you don't know what your doing... Look at the audience I am talking to. They are asking what the colors mean and names of parts... The Tension and Lateral Link adjustments cannot alter your caster unless you fabricate a replacement.

 

[Whiskey11]

It isn't to be played with, especially if you don't know what your doing... Look at the audience I am talking to. They are asking what the colors mean and names of parts... The Tension and Lateral Link adjustments cannot alter your caster unless you fabricate a replacement.

You are making an assumption that the front end alignment can't be changed from the factory. We don't know what, if any, alignment capabilities the front end has from the factory.

As for "not knowing what it does", caster is the least harmful of all alignment settings to play with. Generally speaking it has little to no effect on tire wear in daily driving, certainly far less than camber does and gobs less than toe does. At any rate, suspension alignment settings are very basic and easy to understand. A few minutes searching on Google will yield all the basic information someone needs for a proper alignment to suit their desires and worst case, once the car is in the hands of enthusiasts, we will know what you can "get away with" in terms of alignment... I would worry far less about running "extreme" amounts of Caster than any other alignment setting.

 

[thePill]

You are making an assumption that the front end alignment can't be changed from the factory. We don't know what, if any, alignment capabilities the front end has from the factory.

As for "not knowing what it does", caster is the least harmful of all alignment settings to play with. Generally speaking it has little to no effect on tire wear in daily driving, certainly far less than camber does and gobs less than toe does. At any rate, suspension alignment settings are very basic and easy to understand. A few minutes searching on Google will yield all the basic information someone needs for a proper alignment to suit their desires and worst case, once the car is in the hands of enthusiasts, we will know what you can "get away with" in terms of alignment... I would worry far less about running "extreme" amounts of Caster than any other alignment setting.

Trust me, you won't be able to adjust the caster at the links. Your original assumption is still incorrect.

No, you can not adjust the caster via the Tension or Lateral Links. Nor is Virtual Pivot and MacP the same. You are welcome to show me different instead of not showing me. I am open to new ideas...

 

[JohnZiraldo]

Any comparison pics with the S550 rear and the ATS since this is what the new Slomaro will be using.

I have been trying lots of search arguments, but nothing has turned up any results for ATS, CTS, Camaro, and Alpha suspension design.
The ATS certainly has had some positive reviews about it's suspension, so it must be an interesting and improved design.

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