Project 5.0 Mustang II - Improving the Suspension with Whiteline and KW Part One

by Mike Kojima

In the first segment of our Project Mustang we took the car to the Streets of  Willow Springs and although we liked the car a lot, it was easy to see that its biggest shortcoming was its suspension.  The stock suspension was very soft allowing for a lot of body roll.  There was also a bunch of nose dive and squat.  Even with the car's excellent engine, stiff body structure and good brakes, the car would have an annoying tendency to understeer with the excess dive and squat making the car harder to balance under braking and acceleration.

The suspension was hampering what would otherwise be a very fun car to drive on the track.  Fortunately there are many tuning options for the Mustang chassis and we chose two of the best for our project.  You might realize that we currently have two 5.0 liter Mustang Projects, a Grey automatic that Vince Illi uses mostly for Autocross and this car, the white six speed that is an all around track day machine.

Read more about project Mustang!

Our white Project 5.0 Mustang is a 2013 six speed with the Brembo brake package, perfect for us to build on.  In this installment we will be focusing on the Achilles' heel of the car, its suspension.

We sourced new tubular trailing arms from Whiteline (part number KTA195) to help locate the live rear axle.  The Whiteline arms are adjustable in length which helps adjust the amount of rear antisquat a little bit.  It is also handy for centering the rear tires in the wheelwells on a lowered car.  The stock squishy large diameter rubber bushings are replaced by Whiteline's firm yet compliant urethane parts.  Getting rid of a lot of rubber compliance in a live axle car helps reduce wheel hop.

These trailing arm brackets are unique to Whiteline (part number KBR37).  Whiteline is one of the companies that pioneered correction of suspension geometry issues throughout their product line.  In the case of the Mustang, the rear axle has a slight amount of pro-squat geometry which is sort of unusual.  Most production cars have anti-squat in the rear suspension. We think this is done to make the car less likely to transition to sudden oversteer when the throttle is applied hard in a corner.  However the car is pretty softly sprung and damped so when the throttle is applied hard, the rear suspension compresses through dynamic weight transfer and the pro-squat.  This causes the suspension to sort of over center deeper into the pro-squat range to where the engine's torque load through the suspension links is actually squatting the rear of the car even more causing a drastic amount of squat as well as preloading the rear suspension springs.  The Whiteline brackets relocate the axle side of the trailing arms down lower to where the suspension now has a slight bit of anti-squat in the geometry.  This is better and the car's geometry is actually pretty neutral when the squat of weight transfer occurs.  This frees up the back of the car, making it less bound by torque reaction and helps the rear axle find more grip.  This helps both off the line traction and traction coming off the corners.

Whiteline also replaces the upper third link of the rear suspension (part number KTA141A).  It is much beefier that the stock upper link which is known to break under hard use. It also has less compliant urethane bushings.  Perhaps the link's most profound feature is that the chassis side bushing is eccentric which allows some adjustment of the pinion angle and the amount of antisquat in the rear suspension.  The link comes with the bushing in the highest location which is the minimal amount of anti squat.  We feel that this is probably the best for all around use.  Raising the pivot reduces the quickness of the chassis response to torque reaction which is also important.  The third link is very short due to the production car having to have room for a rear seat.  The result of that shortness is that small changes in the angle of the third link make a disproportionately large difference in how the rear suspension reacts to torque load.


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Sunday, January 12, 2014 9:47 PM
That Watts link swap is beyond cool. Here's some useless trivia though, the Crown Vics/Grand Marquis/Town Cars got a Watts link starting in 98, what about the Mustang? What the hell Ford? I do enjoy the unbiased evaluations of a car's shortcomings regardless of what country it's from and can't wait to see how much better the car does. Will you run the same track with the same brakes and tires? Of course surface temps will be drastically lower, so it's damn near impossible to establish a good apples to apples comparison here to what the initial eval was.
Dusty Duster
Dusty Dusterlink
Monday, January 13, 2014 6:10 AM
Good; you got the updated Whiteline Upper Control Arm.

Also, the "other" Project Mustang isn't on hiatus; it's just had a bunch of little things done to it adding up to one future article.
Monday, January 13, 2014 9:28 AM
"That Watts link swap is beyond cool" - This

Also, those tabbed brackets look pretty flimsy. I couldnt quite tell from the photos but hopefully they aren't a stressed part.
Mike Kojima
Mike Kojimalink
Monday, January 13, 2014 10:41 AM
The brackets are actually very strong.
Monday, January 13, 2014 11:01 AM
Hi, and thanks for the great articles on the 5.0. I have basically the exact same car, with the exact same setup (V3's instead of clubsports). Fun and reliable car! Wanted to ask what type of camber plates are you using?

Also do you have any laptimes for it at other tracks?
Next planned mods?
Mike Kojima
Mike Kojimalink
Monday, January 13, 2014 11:04 AM
We are using the Clubsport camber plates that come with Clubsports. I suggest that if you want camber plates, get the Clubsports.
Monday, January 13, 2014 1:16 PM
Nice parts. That is a lucky 'stang.

The diffencees in the lengths of the 3rd link and the other 2 must make for some rapid changes in pinion angle with ride height. I guess you must have to set them up pretty specifically for the ride height you are running.

Are the whiteline lower link drop brackets designed to idealize geometry at stock ride height, or lowered ride height? I guess you are getting rid of that pro squat, but you can get into it again if you lower the rear a heap, but you won't get as much as you would in stock locations.

Does ford really ship the car with the rearend raw and unpainted? Must be to shave unsprung weight. Haha.

Monday, January 13, 2014 1:21 PM
I was reading one of Dusty's project updates (the one where the panhard bar was upgraded) and I remember reading that Mike Kojima wasn't a fan of the Watts Linkage... Can you chime why that is Mike? Or is my mind playing tricks on me and I never actually read that?
Monday, January 13, 2014 1:44 PM
Does one not normally /raise/ the roll centre to reduce the roll couple? How come the opposite is effective on this car?
Mike Kojima
Mike Kojimalink
Monday, January 13, 2014 2:33 PM
If I was designing a lateral locator it would require welding and fabricating. I would do a really long panhard rod with both ends height adjustable. Simple, light and a lot of control of roll center location.

Just bolting to the stock mounting points in the watts link is very good because it's not length dependent. Short panhard rods have some problems that the Watts link gets around.

For a race car where you are going to be fabricating everything and have a long as possible panhard with total adjustabilty, I would take that for simplicity and flexibility.
Mike Kojima
Mike Kojimalink
Monday, January 13, 2014 2:34 PM
Monkus, a live axle without a lateral locator has a very high roll center and a lot of geometric anti roll, too much for proper side bite, at least in my opinion.
Mike Kojima
Mike Kojimalink
Monday, January 13, 2014 2:36 PM
SM_Clay, with the car lowered, there is a slight amount of anti-squat. With live axles you want this because you don't want some dynamic squat to over center the suspension into pro-squat.
Monday, January 13, 2014 5:14 PM
How much longer can the panhard rod get? I mean looking at the pics it looks almost the full width of the car, would a few inches make that much of a difference?

I'm considering selling my Evo for a Mustang so I'm trying to learn as much as I can about live axles...
Mike Kojima
Mike Kojimalink
Monday, January 13, 2014 10:05 PM
You can get it at least 6 inches longer.
Dusty Duster
Dusty Dusterlink
Tuesday, January 14, 2014 5:08 AM
Steeda makes a weld-in, fully-adjustable panhard rod.
Tuesday, January 14, 2014 10:33 AM
Think that rear diff will develope any oil leaks with the suspension loads that are now going though the diff cover?
Would you notice any difference in the car if the rear swaybar pivots were mounted to the chassis rather than hanging from the axle? There would be some difference in unsprung weight of the axle, if the sway bar pivots were on the chassis. Not sure it would be enough to even matter in the real world though.
Also, I know the companies send you guys this stuff free of charge, but could you include some sort of dollar estimate that "regular Joe" would have to spend to do what you guys are doing in the article? (any article) Sort of like "the parts we installed here have a total street price of about $X,XXX." I know we could go spend an hour or two researching and getting prices, but just to know a ballpark would be helpful. Also can you share alignment specs?
Great articles as usual!
Tuesday, January 14, 2014 11:34 AM
I second the request for MSRP quotes on stuff like this.

The Watts link does seem like an overly complex solution. How short is the factory Panhard rod? Is it approximately level when the car is at stock ride height, or did Ford do something weird with it that introduced a lot of angularity?

I've got an old SN95 with the Steeda 5-link rear suspension (4-link with parallel upper arms and a fully height-adjustable Panhard rod) and have never noticed enough "squirm" to make me switch to a Watts link. I've always wondered what all the fuss was about.
Mike Kojima
Mike Kojimalink
Tuesday, January 14, 2014 12:07 PM
The diff cover is really beefy so I don't think it would flex and leak. The panhard's angle is ok at stock ride height but tweaked when the car is lowered. it is at an angle not parallel to the ground and axle centerline so it would jack some. It could stand to be 6" longer. I would like it adjustable in height too please but that's kinda asking a lot for stock. If I was building one of these for American Iron, I would use a panhard as long as possible with adjustable height at both ends but this is a bolt in street car and the Whiteline watts link works awesome and since you do zero fabrication I think it's really cool. It also relocates the roll center in what I think is about the just right place. A adjustable panhard rod that uses the stock mounts won't do that. As for MSRP, follow the links to the manufactures web sites at the end of the article and take a look!
Friday, January 24, 2014 5:48 AM
I would like to try a Watt link setup on an S197. The behavior of the car is very different between left hand and right hand corners, even more when there's a bump hidden in somewhere along the said corner. The watt link should "equalize" things out back. My car is also on stock springs, so stock ride height.
Thursday, March 13, 2014 7:18 PM
Question: on the upper control arm mount, interior bolt - what did you use to get the stock 24mm bolt to loosen? I put a 1/2" impact on it & it still wouldn't move.
Michael Lin
Michael Linlink
Friday, June 05, 2015 12:38 AM
Do the harder urethane bushings on the control arms have a negative impact on their ability to articulate?
Anonymous User
Anonymous Userlink
Monday, July 17, 2017 11:35 PM
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