Almost daily here at Lethal Performance we are asked what the best & most important components are to upgrade in the rear suspension for the 2015+ S550/S650 Mustangs. What good is horsepower if you can't put it to the ground?
Jared took a trip over to BMR Suspension in Seffner, FL with our 2018 Mustang GT (aka Project Goldmember) to get the “Kelly Aiken” treatment. While there, we were able to pick Kelly's brain on the IRS and it's components. He has a surplus on knowledge on these cars from not only his own car (even planting GoPros underneath to monitor the suspension's activity) but also from the vast amount of fast cars using BMR Suspension, including 2 of the fastest IRS cars in the country.
Based on his experience, we asked him to pick out what he felt were the most beneficial components for these cars, the “Bread & Butter” as he calls it in the video. The following components will support cars going well into the 8s and those wanting to see low 1.2-1.4 60's (If you're faster than that, they have components for that, too!)
In an IRS car there are a couple of issues to address. The first issue is that the entire cradle assembly will move/rock. In our 2018 A10 car, Kelly was able to point out just how much movement there is in a factory setup. The factory cradle bushing has a small lip on the top which is a limiter. On our car, when we launched it at the track, this limiter was hitting the chassis, leaving a witness mark on the body from the cradle moving
CB005 – Cradle Bushing Lockout Kit
Designed to eliminate cradle bushing deflection & wheelhop
80%-90% reduction in fore/aft and lateral cradle bushing deflection
Comes with spacer rings to lock out the top of the cradle bushing so that it doesn't deflect at WOT
Comes with lower bushing mounts to eliminate lower bushing movement, keeping it from dipping down & causing the pinion to rise
BK081 – Spherical Lower Control Arm Bearing
Designed to eliminate cradle deflection & wheelhop
“One of the most important & overlooked components” -Kelly Aiken
Factory bushings are molded from soft rubber & contain voids/air pockets, causing movement of the lower control arm during aggressive launching/driving. The solid spherical setup eliminates these voids, therefore eliminating the control arm movement.
Also keeps the wheels from moving forward due to bushing deflection at WOT
BK051 – Differential Bushing Lockout Kit
Designed to eliminate the voids in the stock differential bushing setup
Locks the differential movement so that breakage of driveline components is avoided
If you're going to do the differential bushings, we HIGHLY suggest upgrading the hardware while you're in there. Not only are the bolts themselves stronger than the OEM pieces, but the kit also plays an integral role in limiting differential movement. In the rear bushing, the stock bolt has a ton of play in it as it is a smaller diameter than it's location. This causes the diff to be able to move, as shown by the bolt being off center in our car, which in turn changes pinion angle, causing vibration & driveline parts carnage (like us breaking our driver's side axle on Project Goldmember). This play in the bolt also leads to the bushing & cradle actually slicing/cutting the bolt when the car is loaded up & launched. No bueno! Then there is the front bushing setup, which is a threaded design from factory. Because the bushing sheer strength is relying on the threaded part of the bolt, it is much weaker than if it were to rely on the shank (or solid) part of the bolt. These are all helped with the hardware upgrade kit.
LP-550179 – Extreme Differential Bushing Hardware Upgrade Kit
Designed as an upgraded version of BMR's RH017 Hardware Upgrade Kit
Upgrades both the front & rear differential bushing bolts to stronger pieces
Sleeve placed in rear diff bushing eliminates void from factory
Front bushing threads are drilled out & bolt is replaced, with bushing sheer on solid part of bolt and a nut in the rear, which is roughly 70% stronger
Continuing on, the following components will allow more fine tuning of the rear suspension:
TR005 – Double Adjustable Rear Toe Rods
Stock stamped steel pieces equipped with eccentric bolt slip & pivot under load, changing the alignment of the rear wheels
BMR pieces keep geometry better during suspension arc due to offset spherical bushing
Come with lockout plates for the mounting point to eliminate the eccentric bolt from factory that turns
Allow for a wide range of adjustment
TCA048 – Vertical Links
Light & strong, while still offering bushing compliance & no increased NVH
Limit range of cradle movement
Only vertical link on the market that has ability to grease/service the bushings ON the car
For more info CLICK HERE!
Note: Vertical links do not fit:
Mach 1
GT350
GT500
2024 GT & Darkhorse w/ rear brembo brake upgrade
