LCA Relocation Brackets - 2011 GT500

[KRS]

0F916215-723B-4E56-86CA-C293C36E42C1.jpegLooking for any opinions or experience with LCA relocation brackets for my 2011 GT500. The car isn’t lowered, it is a PP car so it’s slightly lower from the factory. The car does have upper and lower Roush LCA’s and traction is non-existent. I was wondering if the relocation brackets would help.

[KRS]

04A70426-DF39-417D-B7F1-606713CE09A5.jpg

Here’s the response that I received from Maximum Motorsports, posted with permission of Jack Hidley.

The RLCA relocation brackets change the amount of Anti Squat (AS) in the rear suspension. That has an affect on the how quickly the throttle can be applied. It doesn't really have any affect on the peak traction level, but just how quickly you can get there without wheelspin. The cut and paste below explains the physics of this.

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Antisquat percentage. When a car accelerates forward, weight comes off of the front tires and moves to the rear tires (the total weight on the tires stays constant). This happens because the cg is located above ground height. This is a good thing in a drag car since we want as high a total percentage of the cars weight over the drive tires to maximize traction for forward acceleration. The total longitudinal weight transfer once the car has reached a steady state acceleration is a constant. However how quickly this weight transfers is a function of the antisquat percentage.

If the AS is 100%, the weight transfers instantly. If the AS is 0% the amount of time required is only a function of the stiffness of the springs and shocks in the rear suspension as well as some mass aspects of the car. If the AS is between 0 and 100%, then the time required is somewhere in the middle. When the AS is 100%, none off the acceleration forces from the tire contact patch, that point at the CG of the car, go through the rear springs or shocks, therefore the rear suspension doesn't change ride height under acceleration. When the AS is at any other value than 100%, some of the acceleration forces go through the rear springs and shocks. That has two affects. It causes the rear ride height to change and it delays the weight transfer onto the rear tires. The weight transfer doesn't get to its maximum value, until the rear ride height has stopped changing. Essentially the weight of the car is being put onto the top of the spring. Until the spring stops compressing, the force at the bottom of the spring is increasing.

The main problem with AS less than 100% is that the car doesn't have maximum possible traction until all of the weight transfer has occurred. In a car with a manual transmission, if the engine is revved up and the clutch dropped, the power delivery to the rear tires is nearly instantaneous. If the car has 50% AS, then the tires will start spinning since the power delivered to the rear tires is there instantly, but the peak traction is not. The fact that the peak traction may be there 1 second delayed doesn't change things, since once the tire starts spinning, it isn't going to stop (dynamic cf is always lower than static cf).

With a stock 4-link Mustang rear suspension, lowering the ride height increases the amount of antisquat. At the same time, lowering the car's ride height, reduces the cg height, which reduces longitudinal weight transfer, which reduces weight on the rear tires, which reduces grip for forward acceleration. These two affects tend to cancel each other out.

If the car has a torque arm based rear suspension, the more the car is lowered, the less antisquat the suspension has. However, with a torque arm, the car will have more antisquat than with a stock 4-link at most normal ride heights.

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Assuming the Roush UCA that you have in your car includes the chassis side mounting bracket, then you have a Stop the Hop kit. This has a UCA with a different length and the bracket changes the angle of the UCA in the car. This also changes the amount of AS in the rear suspension. See attached sketch.

You can see in this sketch that the angle of the RLCA or the UCA in the side view both affect the location of the IC. When the IC moves up or down, the amount of AS is usually changed in the process. You can use the formula in the sketch to calculate the amount of AS your car has.

The S197 Mustang has an absurdly low value of AS. This is because the chassis was designed for an IRS and the solid was installed in it, long after all of the critical points were set.

I can tell you how much AS your car has now and what it could have with the MM RLCA relocation brackets installed. If you rad through the installation instructions linked below, it will tell you what the AS values would be with only the MM RLCA relocation brackets installed.

https://www.maximummotorsports.com/a...Mm5RLCA-57.pdf

To do any calculations on your car, I need to know what the part number is for the UCA that was installed, to make sure that it is the one with the revised bracket geometry.

Installation of the MM RLCA relocation brackets will affect the pinion angle a very small amount. The exact amount depends on the UCA installed and the ride height of the car. We have never had a customer complain that the new pinion angle caused any vibration problems.

Sincerely,
Jack Hidley
Maximum Motorsports Tech Support

[ZR]

We've experimented with different set ups in the rear of the '05 since removing the 9" Ford and going back to an 8.8. Current set up is Koni S/A front and rear with Ford Racing lowering springs. For arms, lowers are MM extreme duty, MM relocation brackets, BMR adjustable upper (can't remember if I settled on poly or heim end), panhard is also MM with a BMR chassis brace. Tires are Nitto 555 Gen II (275-40x18). It never ceases to impressive me how well the car drives, how much traction it has in the corners and how composed it feels no matter if the roads in decent shape or not. Straight line traction, while I seldom if ever dump the clutch and launch it, car does see a good amount of foot to the floor hits from a slow roll in first that extend up into 4th. While it always has some wheel spin it's dramatically less vs what you'd expect from the street focused tires I'm running. Car goes dead nuts straight and is controllable enough it feels like you could literally take your hands off the wheel. Would a drag radial or similar make it hook harder, no doubt about it but I'm looking for driving quality over absolute bite.
My opinion, it's impossible to beat the traction and handling of arms like the Extreme duty from MM. Similarly impressed with the same series of lower arms in Ross's SN95. There is no doubt in my mind none of the rubber or poly bushing arms on the market come remotely close to how well these work, well worth the money. Contrary to "internet opinion" they do not add significant NVH (both of our cars, dead nuts quiet). Also worth noting, with one piece steel driveshaft and pinion angle set to what I feel is the hot set up for the street, no matter how far you twist the speedo around (on a deserted Mexican hwy of course) you can't feel so much as a hint of driveline vibration, off throttle coast is just as smooth.