S550 Suspension School - Integral Link IRS

Now that we have it confirmed that the IRS is using an integral link set up, anyone want to go into the advantages of this design? I know the other thread in this forum where we were speculating ILIRS design touched on it but that was mostly speculation based on the Fusion IRS.

Same basic setup/advantages as discussed in these threads?

http://www.mustang6g.com/forums/showthread.php?t=843
http://www.mustang6g.com/forums/showthread.php?t=842

I'm not sure I can point out any advantages in a performance mindset, but supposedly an Integral link setup allows you to run the geometry you want with softer bushings all around since the integral link more evenly distributes brake and acceleration torque to the different arms in the suspension.

Unfortunately with the design seen here we have the lower arm with two bushings that are not in line with each other which means they are going to be in a state of constant bind during bump and droop. I suspect that stiffer bushings in these areas will exacerbate the issue. I don't know if spherical bushings will operate in a non-linear way like that... It certainly will pose some problems for those looking to stiffen up the rear suspension's bushings...

At least, I think so on the last part.

I have been hitting up this topic elsewhere but I will begin to put it here... First, this is basically a copy and paste of an SVTP conversation.

First up, the new DB MacP front suspension. BMW and Mercedes have moved pretty much exclusively away from the double wishbone front suspension to this new MacP system.

The S197's struts are different, and beefer looking. They mount to 2 points on the chassis. The extra link on the new Mustangs front suspension is nothing more than something to keep the forward and aft movement that the single mounting point lower control arm is going to want to do in check. The extra link does the same thing to the new front lower control arms that a panhard bar does for a SRA. It's a totally unnecessary mod for a control arm that mounts to 2 points on the chassis.

I'm sure it works, but the vehicle is supported by front control arms that mount to a single point on the chassis instead of 2. Having 2 links does not mean the new Mustangs front setup is stronger or more robust than the outgoing Mustangs.

S197 front struts:


S550 suspension that you can see the front suspension setup in:


thePill says: Incorrect... The Tension Link and Lateral Link replaced the massive, lower arm. The strut/spring is literally the same. The MacP strut serves as the upper control arm. It has been that way since the Boss 302 in 1969, this MacP system offers greater tune-ability, brake, wheel and tire clearances, weight reduction vs. the S197 MacP system and the cost is relatively the same.

I was initially told the Mustang would use VP suspension (paired with CBIRS)... While the live axle was kicked to the curb, the MacP system evolved. It did so with the approval of most Mustang fans...

Click to expand...

Well yeah when talking a Macpherson strut setup the term strut is used so frequently that you start using it incorrectly.

Going off the picture the Lateral Link is what's supporting the front of the car. Or at least from the knuckle to the chassis. It and the strut setup is what's supporting the cars weight and absorbing the loads that are put on the suspension. Again the Tension Link doesn't make the front suspension any stronger or beefer and better able to sock up a shock any more than a panhard bar does to a SRA they just check to control arms new found tendency to move forwards and backwards during braking, cornering, and just normal driving in check.

I'm sure it does it's job, but it's just like..........Why? The only reason I can think to go to a setup like that is for a weight reduction.

thePill says: No no... On ALL MacP systems, the actual Strut/Spring supports the weight via the forged steel knuckle (aluminum in the future). That Tension link absorbs lateral and twisting forces while the wheels turn under steering. The Lat Link also absorbs lateral forces (like the new IRS's IL Link). These two links can be tuned independently for camber and toe...

The old MacP systems were only a single A link that could not be adjusted at all. It didn't matter because the SRA couldn't either...

The 5th Gen uses the old MacP system and an IRS... Who told them that would be a good idea is beyond me. IRS can be adjusted, MacP can't... If Ford stuck with the old MacP system, they would be able to tune the rear suspension but not the front like the 5th Gen Camaro... Stupid if you ask me...

Click to expand...

Yes you are correct the strut is supporting the weight of the vehicle. What I'm trying to say is the lateral link on this car is whats having to support the abuse that's going to get put on the control arm/arms. In fact it is the front control arm basically. If it works well then great. I hope so. It looks to be a noticeably lighter setup. I'm just resorting back to Fords history of trying to re-invent the wheel so to speak when coming up with their suspension setups. They try to be too smart and innovative, but not in terms of advancing the design, but in simplifying and lessening it's cost. Examples are the Foxbodies angled upper rear controls arm which were tasked with not only doing the traditional job of a upper control arm on a SRA, but also the panhard bars job so that they could not have to use a panhard bar or watts link. It was a very poor design, as was the Modified Macphersons. I don't necessarily think that it's general design was bad as much as it was just a bunch of cheap stamped steel with poor geometry for the car. Twin I-Beams are another example of a less than stellar design from Ford.

You're saying that the Tension rods, and Laterial links(lower control arms) allow you to adjust the alignment on the car when working in conjunction with one another? I'm sure adjustable links will become a very popular mod with the S550 then. One thing I've been wondering is how the tension link is going to affect tire clearance. It looks awfully in the way of a big front tire trying to turn sharp. Hopefully I'm wrong.

IDK we'll just have to see how the car does. I'm sure it's going to be very good, I'm just not sure it's going to be good enough to match the performance potential of the next Generation of it's main rival which I feel Chevrolet is going to work real hard at making very good, and resolving some of the issues with the Gen5.
thePill says:Ah, I do understand the concern about the new Tension and Lateral links durability. Try not use the "size" of the control arms as a benchmark. Instead, try to imagine the "efficiency of design" and what improvements could be made over a steel casting. The same principle was used in the new IRS in what they call the "Integral" Link.

Before, Control Blade used HUGE trailing arms to do what the IL links do now... Just 1/64th the size...

It is easier to beef up those two links when needed (if needed).

Advantages are...

Larger disc brakes
Larger wheel width
Wider tire
Less Weight
Adjustable front Toe angle
Adjustable front Camber angle
Same cost (maybe cheaper by now)
Possibly greater durability using advanced forging techniques and metals.
Less moving parts then traditional Double Wishbone AND more durable
More tune-ability then the previous MacP strut.

This is not the Fox body...
This is not the SN95......
This is not the S197........
This is not the old Mustang.............

This is not the old Ford......................

Edit: Besides, it would be the bushings that fail and those can't get any stronger.

Click to expand...

Whiteline and BMR will have a slew of parts out for the 2015 within weeks of the on-sale date.
...and I'm sure both those companies will offer quality products as they always do.

I am merely pointing out that the MacP Double Pivot suspension is no weak link. In fact, BMW uses primarily this same system in the "All Aluminum" form.

Mercedes Benz did this in 2007 with the SLK.

Quote:
The previous double-wishbone front suspension with recirculating-ball steering has now been superseded by a three-link axle featuring McPherson spring struts and a rack-and-pinion steering system. This new axle technology revolves around two individual link elements which serve as torque and cross struts. Apart from more precise wheel location, the prime benefit offered by these two links is the ability to compensate for vibrations caused by tyre imbalances or brake force fluctuations more effectively than rigid wishbone designs. Added to this is the fact that, in the event of a frontal collision, the crumple zones in the vicinity of the bottom link level are larger, allowing the front end of the vehicle to absorb more of the impact energy. The torque struts of the SLK’s front axle are made from aluminum, whilst the cross struts are manufactured from forged steel.

On the SLK the links are called the "Torque" and "Cross" links on their MacP Double Pivot. The S550's MacP system uses a "Tension" and "Lateral" link. Tension=Torque link, Lateral=Cross Link.

The C209 CLK

BMW calls it their Double-Joint Spring-Strut Front Suspension. It is BMW's premier front suspension. BMW markets their Tension/Lateral Link (Torque/Cross Link on the Mercs) together as the "Track Control Arms"... I like it.

Click to expand...

Just so you are aware, the new front suspension IS a virtual pivot point front suspension it's just not the short-long arm variant of it. If you draw a line through the ball joints and the center of the bushings at the chassis side you will see they intersect outside of the hub. That is the point in which the front suspension "rotates" around, hence virtual pivot point.

The advantages here comes from the ability to run higher offset wheels without running into scrub radius issues. On top of that it changes steering feel. This allows for the larger brakes.

Mercedes goes to a pretty big extreme on their variations of the offset lower control arms. This is a W212 E63 and I haven't seen them this offset in any other Mercedes I've worked on.

S550 Suspension School

Now that all the excitement from announcement day is over, let's get back to school.

Any of you folks that are far more knowledgeable than I, have the insight or skills to explain the forces going on and the purposes of the different components in these diagrams?





For example, do you know of any simple diagrams maybe showing a stick figure of suspension links with an explanation of what forces are at play and how the 'Lateral link', 'Tension link', 'Toe link', 'Upper Camber link', 'Integral link', and yes, even the 'Stabilizer bar' are controlling those forces?

I'm ashamed to admit that when I look at these pretty colored diagrams, the only things I truly understand are the struts, shocks, and springs.

It is the Green > Red > Yellow pathway I bet that will be the primary place where wheel hop will happen. The rest is the right-left stuff which typically is not as violent. I hope Ford does all of it correctly. It definitely is not as easy to imagine the force vectors these days.

JohnZiraldo said:

Now that all the excitement from announcement day is over, let's get back to school.

Any of you folks that are far more knowledgeable than I, have the insight or skills to explain the forces going on and the purposes of the different components in these diagrams?

For example, do you know of any simple diagrams maybe showing a stick figure of suspension links with an explanation of what forces are at play and how the 'Lateral link', 'Tension link', 'Toe link', 'Upper Camber link', 'Integral link', and yes, even the 'Stabilizer bar' are controlling those forces?

I'm ashamed to admit that when I look at these pretty colored diagrams, the only things I truly understand are the struts, shocks, and springs.

Click to expand...

DON'T BE FOOLED BY ALL THE FANCY LINK NAMES.



First, lets talk about the front suspension or DB MacP. In most suspension, you will have a knuckle. Even Double Wishbone uses a Steering knuckle as well as Virtual Pivot. The "Knuckle" connects the wheel to all the independent moving parts. It's the hub...

At first glance, we can see there is no "Wishbone" or visible upper or lower control arm. This is not like Short-Long-Arm suspension... The strut itself is in fact the upper control arm. It connects to the knuckle, which is currently forged steel (weight loss eventually).

The Stabilizer bar... We should already know this.

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"

We can see the "Tension" Link above is the Toe. Just because something moves independently doesn't mean its adjustable so, adjustable (or desired length) may need to be aftermarket. It does allow Ford the maximum tune-ability because they can select the best setting during testing. The Lateral Link stabilizes the camber as well as tunes that setting.

The "Dual Ball Joints" are the main reason this system is used instead of the old MacP system. It allows for larger disc brake sizes, which Ford seems to be taking advantage of right away. It also allows for some thicker wheel and tire up front. The Tension and Lateral Links replace the old MacP's Lower Control Arm. It was heavy and it bound the toe and camber together (not good)...

Moving to the rear, the Integral Link Independent Rear Suspension is a light-weight IRS system that eliminates the Control Blades bulky upper sub-frame and the "Control Blades" themselves. This suspension uses an actual Lower Control Arm called the "Lower H-Arm".

The Knuckle in the rear is Aluminum, we could see this move to the front in a few years. Stabilizer bar needs no explanation as it is the same in operation as the front. Ford didn't get fancy with the names back here like the front. Toe link stabilizes the Toe angle. The Upper Camber Link is the opposite of the front suspensions Lateral Link. The IRS's Camber Link is an "Upper" control link while the front uses a "Lower" Lateral Link.

The system gets it's name from the Integral Link. The Integral Link's operation and function is similar to the Control Blade in the CBIRS system... only it's 1/64th the size of the trailing arm in the Control Blade set up.

The Integral Link's mission is to absorb the same forces the Control Blades did (Squat/Dive). It can also eliminate wheel hop which is another force it absorbs.

The system uses traditional strut/spring config and looks like it is not set up for coil-overs.

thePill said:

DON'T BE FOOLED BY ALL THE FANCY LINK NAMES.

First, lets talk about the front suspension or DB MacP. In most suspension, you will have a knuckle. Even Double Wishbone uses a Steering knuckle as well as Virtual Pivot. The "Knuckle" connects the wheel to all the independent moving parts. It's the hub...

At first glance, we can see there is no "Wishbone" or visible upper or lower control arm. This is not like Short-Long-Arm suspension... The strut itself is in fact the upper control arm. It connects to the knuckle, which is currently forged steel (weight loss eventually).

The Stabilizer bar... We should already know this.

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"

We can see the "Tension" Link above is the Toe. Just because something moves independently doesn't mean its adjustable so, adjustable (or desired length) may need to be aftermarket. It does allow Ford the maximum tune-ability because they can select the best setting during testing. The Lateral Link stabilizes the camber as well as tunes that setting.

The "Dual Ball Joints" are the main reason this system is used instead of the old MacP system. It allows for larger disc brake sizes, which Ford seems to be taking advantage of right away. It also allows for some thicker wheel and tire up front. The Tension and Lateral Links replace the old MacP's Lower Control Arm. It was heavy and it bound the toe and camber together (not good)...

Click to expand...

You were doing so well until you started talking about alignments. Caster IS to be played with, any sane person would want plenty of Caster. The S197 chassis shipped with +7.0º of caster which is good when compared to the Fox/SN95 cars which had around +4.5º. Why is Caster important? Caster is important for two reasons: First the self centering aspect of caster (think caster wheels on a shopping cart) helps keep the car stable at speed... More importantly is caster turns to camber when the wheel is turned which helps keep the tires flatter to the pavement... Specifically caster turns to negative camber on the outside wheel of a corner and positive camber on the inside wheel while cornering.

The Tension link will also adjust camber, but at a much lower degree. It will adjust camber because it is not perfectly longitudinal in its orientation as it has a lateral component as well. The Lateral link will have a great deal more adjustment than the Tension link but to say it wont change camber at all is wrong. I also wouldn't use it to adjust toe either since any adjustment in it's length will have a profound impact on your camber settings. The component of the front suspension that should be used to set toe is the steering rack. What the tension link will have some impact on is bumpsteer which will make tuning bump steer a bit more complicated than just a different tie rod end for the steering rack.

Finally, not all double wishbones have a virtual pivot setup. The virtual pivot point is by virtue of the dual ball joint on one of the "arms" (in this case the lower "arm" consists of two separate linkages)... the virtual pivot point is the point in space where the lines drawn through linkages intersects. This changes the effective pivot point to further out, which allows for lower offset wheels to clear larger brakes without absolutely destroying tires due to the increase in scrub radius.


Your post on the rear seems to be spot on. I'll try and post more when I get off work in 6.5 hours!

Here is a little YouTube video demonstrating caster, camber, and toe for techno-dummies like me who don't like to read long explanations.

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Again keeping with the idea of not having to read a lot, here is another YouTube video that explains the Stabilizer-Anti-Roll-Sway Bar.

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Wikipedia has an extensive description of suspension components and terms here:
http://en.wikipedia.org/wiki/Suspension_(vehicle)

I have not been able to find any website though that describes how badly the S550's new suspension architecture will be embarrassing the Camaro's.

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

No, Virtual Pivot uses a double wishbone.

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