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S550 Suspension School - Integral Link IRS

Trackaholic

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DBJ allowing bigger brakes does not compute. DBJ actually consumes more space in the DBJ area.
My take from his comment (and I believe also shown by the BMW suspension animation) is the virtual pivot allows a larger brake for a couple reasons:
1. The motion of the two lower links causes them to move away from where the wheel rim would otherwise travel.
2. The virtual pivot allows the wheels to be pushed further outboard without causing greater scrub. This provides the greater caliper clearance you mentioned.

So, I think his comment was accurate, but just the tip of a chain reaction of changes that leads, in the end, to a better brake and tire package.

Although, you say those same brakes and wheels already fit on the current Mustang, so :headbonk:

-T
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Whiskey11

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My take from his comment (and I believe also shown by the BMW suspension animation) is the virtual pivot allows a larger brake for a couple reasons:
1. The motion of the two lower links causes them to move away from where the wheel rim would otherwise travel.
2. The virtual pivot allows the wheels to be pushed further outboard without causing greater scrub. This provides the greater caliper clearance you mentioned.

So, I think his comment was accurate, but just the tip of a chain reaction of changes that leads, in the end, to a better brake and tire package.

Although, you say those same brakes and wheels already fit on the current Mustang, so :headbonk:

-T
Number 2.) is where my money is. Remember that the front track is remaining basically unchanged and we can only assume that front fender space didn't change much. I wouldn't be surprised if the front suspension didn't have very similar geometry to the S197 chassis in terms of SAI and scrub radius. About the only advantage for fitting brakes there is the fact that you can run a lower offset wheel... IE: 45 offset S197 wheels might be sucked in like crazy, the 38's might still be sucked in but we wont know until we get them on the car and something like 25 is going to be the new offset for flush fitting?

I honestly can't say I know but the S197 could already swallow the 15" brake rotors and 6 pot Brembo Calipers with 19" wheels (and one 18" wheel, BBS ironically) so it's not like the S197 was deficient in that area, it's just that you were constrained far heavier on the S197 in wheel offsets for outboard wheel well clearance.

qwkcoupe, IRS %AS is measured from the IC created by the side view intersection of the control arm angles and the line drawn through the center of the wheel hub (not the tire contact patch like on a live axle).



Changing the angle of the arms will change %AS
 

thePill

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I think the greastest advantage over the S197's front suspension would be tune-ability. It appears the DB MacP system has NO traditional upper control arms. Like the old S197 MacP system, however, it had a larger, fixed, one piece, lower control arm. DB uses two, smaller and vastly more tune-able lower control arms. This is where the "Double Ball Joints" are shared with Ford's out going Virtual Pivot Control Link, the links are somewhat similar but design slightly different. The upper control arm retains the MacP strut...

It looks like a lighter system for sure and the design of the lower control links (Tension and Lateral) are likely more efficient.

Why did Ford need to do this? Even if the S197 could fit a 15 inch disc, the new S550 went through other changes. Ride height and turning radius all need to be factored into the new system.

You do realize that no SLA setup has converging upper and control arm links at one point on the back of the spindle right? That would be the most useless SLA setup known to man kind and would still require something to keep the wheel upright. That picture is clearly plan view (top down), in which case there is no specific need for an upper and lower control arm, just two arms with separated ball joints on the same plane or near the same plane such as the S550's lower control arms. You could also have two upper arms as well for added tuneability. The strut configuration works the same way only it is just the lower arms. Think of the strut bearing plate as the upper ball joint on an SLA setup.

Yes, since ground clearance requirements has eliminated true double wishbone as an OEM option, both Short/Long Arm and MacP systems had to evolve. This is where the term "Virtual Pivot" came from.

I'm not sure what you mean by two links that push and pull. The lateral link, at least from what we have seen, is purely lateral, IE, no ability to push or pull the suspension fore/aft or in any direction but under lateral loads. The Tension link certainly carries the fore/aft forces created by the tires as well as some of the lateral forces. The lower control arms on the S550's strut setup creates a virtual pivot point which is the lower point of two that the suspension rotates around. The other point is the upper strut bearing plate and the line between them is known as the steering axis inclination. By using two ball joints on the lower "arm" you move the SAI away from the bottom of the spindle.


For the "Push/Pull" of the DB MacP systems... Since there is NO one piece lower control arm, the two lower control links need to form a "VIRTUAL A-ARM" (there is that word again). Virtual means "Imaginary" and can only do this by applying force (both pull/push) at the steering knuckle. The strut serves as the upper arm and keeps the knuckle level. (simple terms)


I'm not sure who the heck you think is suggesting that it does. NO one is disputing that the S550 front suspension is a strut based setup, what I'm disputing is your assertion that the lower arms do not form a virtual pivot point, you know, that thing you seem to think can only be formed by an SLA setup.

I thought you were specifically talking about Ford's Virtual Pivot Control Link suspension. We had a thread on this site dedicated to just that suspesion. In order for the suspension to be VPCL, it absolutely needs an upper control arm. I was under the impression everyone here understood that VPCL is not on the S550. It is an evolved version of the S197's suspension.



I also don't agree with your assertion that it is being done for more clearance for brakes, wheels or tires. The S197 chassis, with a conventional MacPhearson strut setup could quite easily swallow 18x11" wheels with no poke and very little need for additional negative camber. It could also swallow 315's with ease. On the brake front, the same 15" rotors and 6 pot calipers in the new GT PP were standard on the 2013-2014 GT500's which used the same conventional strut setup as the rest of the S197 chassis. There are noticeable gains in front end grip from using the S550 type suspension. Sure, you'll gain the ability to use lower offset wheels which creates brake clearance with the spokes but that was hardly a problem on the S197 chassis.

The S550 made some changes to the ride height, mounting points, strut angle and other things. All those changes combined could have affected the turning radius. Therefore, in order to improve the car overall, several changes had to be made.
 

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I also don't agree with your assertion that it is being done for more clearance for brakes, wheels or tires. The S197 chassis, with a conventional MacPhearson strut setup could quite easily swallow 18x11" wheels with no poke and very little need for additional negative camber. It could also swallow 315's with ease. On the brake front, the same 15" rotors and 6 pot calipers in the new GT PP were standard on the 2013-2014 GT500's which used the same conventional strut setup as the rest of the S197 chassis. There are noticeable gains in front end grip from using the S550 type suspension. Sure, you'll gain the ability to use lower offset wheels which creates brake clearance with the spokes but that was hardly a problem on the S197 chassis.
I'm also skeptical on the reasoning of the S550's dual-link (dual ball-joint) LCA's for "wheel and brake clearance" because you can make an A-frame lower control arm that connects the two inboard chassis points on the S550 to only one balljoint on the upright -which would have the same clearance.

I think the reasoning for the move to the dual ball-joint/dual-link lower arms of the S550 has more to do with the scrub radius and wheel arc.

Look closely at both of the lower links. They do not stay stationary like the A-frame LCA of the S195, but BOTH actually rotate about the inboard pivot a few degrees. This would mean that the 'virtual-pivot point' of the tire (intersection of the line drawn through both of the arms) changes longitudinally with steering movement.

I'm not sure you understand what you are typing because you make it sound as if a strut suspension has no upper pivot point on which the suspension rotates around. That is false.

The upper pivot point is the upper strut mount bearing. The lower pivot is the virtual pivot point created by the intersection of lines drawn through the chassis side pick up points of both lower control arms and both lower ball joints. On a strut based suspension the strut is the upper control arm, you said it yourself in this very thread.

Here is the F30 M3's front suspension setup:
There has to be more of a benefit going on with this dual lower control arm design than meets the eye -especially in regards to how the wheel and tire rotate thoughout the steering arc since it does not have a defined pivot point like in a standard A-frame LCA design.

BMW went to this LCA layout in the E90 and F30 3-series Chassis generations, leaving the traditional lower A-frame design (like the S197) in the E30, E36 and E46 generations. It's also interesting that the Mustang has the integral link -which BMW also used in their E38, E39, E53, E60, E63 generation cars.
 

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I'm also skeptical on the reasoning of the S550's dual-link (dual ball-joint) LCA's for "wheel and brake clearance" because you can make an A-frame lower control arm that connects the two inboard chassis points on the S550 to only one balljoint on the upright -which would have the same clearance.

I think the reasoning for the move to the dual ball-joint/dual-link lower arms of the S550 has more to do with the scrub radius and wheel arc.

Look closely at both of the lower links. They do not stay stationary like the A-frame LCA of the S195, but BOTH actually rotate about the inboard pivot a few degrees. This would mean that the 'virtual-pivot point' of the tire (intersection of the line drawn through both of the arms) changes longitudinally with steering movement.


There has to be more of a benefit going on with this dual lower control arm design than meets the eye -especially in regards to how the wheel and tire rotate thoughout the steering arc since it does not have a defined pivot point like in a standard A-frame LCA design.

BMW went to this LCA layout in the E90 and F30 3-series Chassis generations, leaving the traditional lower A-frame design (like the S197) in the E30, E36 and E46 generations. It's also interesting that the Mustang has the integral link -which BMW also used in their E38, E39, E53, E60, E63 generation cars.
We will have to wait for Ford to comment to know for sure. I suspect it has something to do with the body mounting location changes, the struts new caster angle, the new ride height and possible steering radius issues.

Ford wanted a lower ride height and they got that... Just using the BMW's pic above, imagine what that disc may run into if the whole ride height was lowered. Their "Tension" link could have clearance issues with the disc... I would have to see what changes were made in the caster too but I suspect that ride height is one of the main reasons the disc and tension link could make contact. The lateral link is tucked away... This should not only allow Ford to use 15 inch plus disc brakes but, they also lowered the ride height a bit...
 

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We will have to wait for Ford to comment to know for sure. I suspect it has something to do with the body mounting location changes, the struts new caster angle, the new ride height and possible steering radius issues.

Ford wanted a lower ride height and they got that... Just using the BMW's pic above, imagine what that disc may run into if the whole ride height was lowered. Their "Tension" link could have clearance issues with the disc... I would have to see what changes were made in the caster too but I suspect that ride height is one of the main reasons the disc and tension link could make contact. The lateral link is tucked away... This should not only allow Ford to use 15 inch plus disc brakes but, they also lowered the ride height a bit...
I doubt the disk would ever hit the tension link, but I'd be more worried about it hitting the steering rack arm when lowered... I'm willing to bet Ford has thought of this already since they do use the factory steering racks (without the daily driver nannies in it) on the factory race cars (Boss 302R Boss 302S). I would think they would have thought of that long before the car hit production.
 

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We will have to wait for Ford to comment to know for sure. I suspect it has something to do with the body mounting location changes, the struts new caster angle, the new ride height and possible steering radius issues.

Ford wanted a lower ride height and they got that... Just using the BMW's pic above, imagine what that disc may run into if the whole ride height was lowered. Their "Tension" link could have clearance issues with the disc... I would have to see what changes were made in the caster too but I suspect that ride height is one of the main reasons the disc and tension link could make contact. The lateral link is tucked away... This should not only allow Ford to use 15 inch plus disc brakes but, they also lowered the ride height a bit...
Where did it say that Ford wanted a lower ride height? They did lower the roof, hood, and trunk but it does not look to be at a much lower ride height.

How would the tension link have clearance issues with the rotor? I'm not sure how they would come in contact even with a lower ride height.
 

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Where did it say that Ford wanted a lower ride height? They did lower the roof, hood, and trunk but it does not look to be at a much lower ride height.

How would the tension link have clearance issues with the rotor? I'm not sure how they would come in contact even with a lower ride height.
Ford said it. They released the numbers somewhere but I can't seem to find them right now. I'm sure someone else knows where they are.
 

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Where did it say that Ford wanted a lower ride height? They did lower the roof, hood, and trunk but it does not look to be at a much lower ride height.

How would the tension link have clearance issues with the rotor? I'm not sure how they would come in contact even with a lower ride height.
Ford initially drew attention to that over anything else...

This new Mustang sits lower and wider than before
...and was presented as such.

The new sixth-generation Mustang features a sleeker design with a lower, wider stance and bolder dual grille.
I doubt the disk would ever hit the tension link, but I'd be more worried about it hitting the steering rack arm when lowered... I'm willing to bet Ford has thought of this already since they do use the factory steering racks (without the daily driver nannies in it) on the factory race cars (Boss 302R Boss 302S). I would think they would have thought of that long before the car hit production.
There would be very little risk in the BMW design. The S550's Tension Link runs parallel to the stabilizer...

There is a long shot possibility that the disc, especially a 15 inch disc, could make contact to the Tension link (Red) on a sharp right hand turn. As you said though, it looks safe and there looks to be plenty of clearance.






You can see the clearance here...
 

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Ford initially drew attention to that over anything else...

...and was presented as such.

There would be very little risk in the BMW design. The S550's Tension Link runs parallel to the stabilizer...

There is a long shot possibility that the disc, especially a 15 inch disc, could make contact to the Tension link (Red) on a sharp right hand turn. As you said though, it looks safe and there looks to be plenty of clearance.

You can see the clearance here...
All of the "lower and wider" comments can easily be interpreted by the lower roof, hood, and trunk and wider stance. In terms of a lower ground clearance, due to the design parameters of acceptability for approach angles and underbody clearance, I would be surprised if the car had a lower ride height. From the photos online, it appears to be at the same ride height as the S197.

In regards to the tension link clearance, because the rotors sit inboard of the wheel and tire, the wheel would most likely be what would contact the tension link at full lock. Not the rotor.
 

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thePill

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All of the "lower and wider" comments can easily be interpreted by the lower roof, hood, and trunk and wider stance. In terms of a lower ground clearance, due to the design parameters of acceptability for approach angles and underbody clearance, I would be surprised if the car had a lower ride height. From the photos online, it appears to be at the same ride height as the S197.

In regards to the tension link clearance, because the rotors sit inboard of the wheel and tire, the wheel would most likely be what would contact the tension link at full lock. Not the rotor.
There was also talk about the strut tower height being lower as well but I'm still not sure if that is true. I guess if they are celebrating about the lower hood, it would suggest everthing else stayed the same... But then again, how can that be on an All-New Platform?

Edit: When I say the tower height is lower, I mean the tower mount is lower. Closer to the datum plane.
 

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The entire shell sits lower on the suspension. This move alone will have a huge impact on handling. This MacP system is lighter by far and very efficient in terms of efficiency of parts. The lower control links work together as the lower "A" Arm ll while serving the toe and camber roles. The Strut still serves as the upper control arm... The aftermarket will offer Tension and Lateral Links no doubt...
 
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I just posted these in another thread but here's the first shots of the new IRS in a production S550 that I've seen. This is from the 2015 car they showed at PRI.

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