Tech Tips: BMR S550 Rear Suspension Components

 

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 Mustangs. What good is horsepower if you can't put it to the ground?

Jared & Christy 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. Check out the video & scroll down for tons of info!

 

 

We've created some awesome packages with all of the components recommended for you and your setup, from mild to wild. There is the Biscuits & Gravy package, the Bread & Butter package & lastly the Steak & Potatoes (with a side of NVH) package. Check all of the options out below to see which one is best for YOUR application. 

 


Biscuits & Gravy Suspension Package (aka Level 1)

 

First, we brought you the "Bread & Butter" package, a collab between Lethal Performance & Kelly Aiken of BMR Suspension. While that kit has become hugely popular, it may be overboard for some of you who daily drive your car but still want to harness that power at the track. Or maybe you road race the car, hit HPDEs or just like to race it on the weekends. We worked with Kelly to put together the bare essentials, a starter package, for the 2015-up Mustang GT. These parts have seen 9 second runs & even 1.3 60's at the track. This is a GREAT place to start. 

The "Biscuits & Gravy" package includes: 

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
  • Click here for more info


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
  • Click here for more info


CB010 - Cradle Bushing Lockout 

  • Reduce Wheelhop, bushing deflection, and cradle movement
  • Built from 6061-T6 billet aluminum and stainless steel
  • Billet aluminum upper bushing lockout rings capture the inner bushing sleeve (front and rear) and the outer lip of the bushing cup on the cradle (front)
  • Lower bushing locating washers (front) capture the bottom portion of the bushings’ inner sleeves
  • Movement on any plane (fore/aft, lateral, and vertical) is nearly eliminated
  • Click here for more info

 

Click here for the "Biscuits & Gravy" package.

 


Bread & Butter Suspension Package (aka Level 2)

 

Based on his experience, we asked Kelly of BMR to pick out what he felt were the most beneficial components for these cars, the “Bread & Butter” as he calls it in the video (hence the name!). These chosen components will support cars going well into the 8s and those wanting to see low 1.2-1.4 60's.

The "Bread & Butter" package includes: 

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 (see image).

 

 

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
  • Click here for more info

 

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
  • Click here for more info

 

Another issue to address on the IRS is the movement of the differential itself within the cradle. While looking under our car, Kelly was able to also show us the tell tale signs that our diff had moved from our track ventures. The first place to look are the front differential bushings. The factory bushings have small metal alignment nubs built in. On a factory car, these protrusions are barely visible (or not visible at all) however on our car, the passenger side was sticking way out and the driver's side only slightly out. This tells us that the diff moved enough to compromise the clamping force of the bolt & also stayed seated in a diagonal position.

 

 

Next, we looked at the rear differential bushings & bolts. It was clear here, also, that the diff had moved as the bolt on the passenger side was sitting much higher on the bushing than it was on the driver's side.

 

 

Want to sort that out? Here's what you need:

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
  • Click here for more info

 

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
  • Click here for more info
  • For those that don't wish to drill out the front bushing, you can use BMR part no. RH017found here, which supplies just a stronger bolt replacement 

 

 

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
  • Click here for more info

 

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
  • Click here for more info

 

Click here for the "Bread & Butter" Suspension Package.

 


Steak & Potatoes (with a side of NVH) Suspension Package (aka Level 3)

 

The "Steak & Potatoes" suspension package is catered to those who are hardcore about racing their car at the track. The S&P package is essentially the Bread & Butter package on steroids. It is a total IRS solution that solidly mounts the subframe and differential to the chassis.

Not only does the package add springs & a few other components on top of the Bread & Butter package, but some of the pieces are replaced with their stronger, more solid counterparts. For example, the solid IRS subframe bushings (BK048) are used in lieu of the cradle bushing lockout kit. The solid differential bushings (BK050) are used in place of the more street friendly differential bushing lockouts & hardware upgrade kit (the bushings are now solid & will not put damaging loads onto the fasteners that tend to break in the factory setup so the need for the stronger hardware is eliminated). Also, the rear lower control arm bearing (BK055) is a stronger, more solid piece than the spherical bearing (BK081) included in the Bread & Butter package.

This aggressive setup will surely get your car launching & 60-footing with some of the fastest cars on the track. In fact, these are the very same parts that are on the ONLY two S550 IRS cars to currently go 1.1X sixty foot times. 

PLEASE NOTE: With these solid components you will experience an increase in NVH and a rougher ride on the street.

The "Steak & Potatoes with a side of NVH" package includes: 

SP089 Front Springs

  • Designed for the street/performance enthusiast
  • Lifetime warranty against sag
  • Linear spring rate offers plenty of support, keeping the body flat and level in the corners, while remaining soft enough for a comfortable ride on any road
  • Click here for more info


SP088 Rear Springs (or SPH767 for MagneRide equipped cars)

  • Designed for the drag race crowd who want to the ultimate in straight-line acceleration
  • Feature a fine-tuned spring rate (800 lb/in rear) to give you great handling and a smooth ride
  • Linear spring rate offers plenty of support, while remaining soft enough for great weight transfer
  • Lifetime warranty against sag
  • Click here for more info


BK055 Rear Lower Control Arm Bearings

  • Eliminate bushing deflection, transferring power instead of absorbing it
  • Drastically decreases lower control arm movement by solidly linking the rear portion of the lower control arm to the cradle, eliminating the factory rubber bushing "voids"
  • Reduces wheelhop and increases handling
  • Click here for more info


BK048 Solid IRS Subframe Bushings

  • Eliminates rear cradle movement
  • Increases the rigidity and stability of the chassis to provide maximum control and consistency
  • Minimizes differential movement by replacing the soft rubber stock bushings with solid two-piece Delrin bushings
  • Click here for more info

 

BK050 Solid Diff Bushings

  • Eliminate differential movement and pinion rise over the factory rubber bushings
  • Replaces the soft rubber OE bushings with four solid two-piece aluminum bushings
  • Click here for more info


TR005 Adjustable Toe Links

  • 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
  • Click here for more info


UTCA064 Camber Links

  • Greasable, solid Delrin bushings add a solid, more responsive feel over the stock rubber bushings
  • Internally fluted, which allows grease to evenly coat the inner sleeve; the flutes also direct grease to the outer edge of the bushing, keeping the thrust surface lubricated
  • Work best for drag racers who have lowered ride heights and are looking for ZERO camber
  • Designed longer than factory length to correct suspension geometry on lowered S550s
  • Greatly reduces bushing deflection
  • Click here for more info


TCA045 Vertical Links

  • Eliminates vertical link flex, giving you much improved repeatability on the street, starting line, or in the corners
  • Solidly link the spindle to the lower control arm, eliminate deflection and wheel alignment changes
  • Click here for more info


Ford Performance M-5A460-M Knuckle Toe Bearings

  • Replaces the rubber Toe Link Bushing in the rear knuckle with a production style bearing
  • Removes suspension compliance with minimal impact to ride quality
  • Improves handling, especially in power down situations
  • Click here for more info



Optional Add-Ons:
VIK-B358AM Vi-King shocks (recommended for drag race use)
Koni Adjustable Front Struts (recommended for cars with 1000+rwhp)

 

Kelly & BMR Suspension have been badass enough to even supply shock & alignment settings when using their complete setup! Click here to check it out.

 

Click here for the "Steak & Potatoes (with a side of NVH)" Suspension Package.

 


 

There are many more suspension components that BMR Suspension offers and that you, the customer, can upgrade but these are the basics & will definitely help to get you to where you want to be on the track. Give us a shout with any questions at 877-2-LETHAL or by email at support@lethalperformance.com.