What do you get when you mix the front suspension from a Mercedes S-Class, the rear suspension from an E-Class and the transmission from a C-Class? The 2005-‘10 Chrysler rear-wheel-drive LX platform.
The LX platform includes the 300, Magnum and Charger. In 2008, the platform was shortened for use in the LC platform in the Challenger.
All of these vehicles have rear disc brakes with the parking/emergency brake mounted in the hat of the rear rotor.
All calipers, except the SRT version with Brembo brakes, are equipped with phenolic pistons. These help to reduce noise and limit the transfer of heat to the brake fluid.
Reports have surfaced that some rebuilders are using steel pistons for replacement calipers instead of phenolic pistons, which can cause problems with brake fade and noise because this brake system was designed to use phenolic pistons.
Be careful when pushing the pistons back. Chrysler advises that no tools should come in contact with the pistons. They even specify that a piece of wood should be used.
Most calipers on the LX platform are cast aluminum, and technicians should be careful when removing hardware due to galvanic corrosion. Also be careful when installing new banjo bolts in order to prevent stripping. The front caliper bolts may look large and beefy, but they have a torque spec of 44 ft.-lbs. In the rear, it is 23 ft.-lbs.
If the vehicle has a 2.7 or 3.5 V6, the majority of the time it will have single-piston floating front calipers; V8 models will have dual-piston front calipers. In the rear, upgraded models have larger vented rotors and different calipers. The all-wheel-drive models all receive the upgraded brakes. R/T models are equipped with four-piston Brembo calipers and rotors.
The latest versions of the LX platform have an interesting piece of programming written into the ABS system that is designed to manage the gap between the rotor and the brake pad. The system is designed to produce the least amount of brake drag and the best possible initial pedal feel. The system works after the brakes are applied and pulls the pistons in a small amount after a stop. This is basically an electronic version of GM’s quick take-up master cylinder of the late 1970s.
On R/T and SRT models, if the system senses a high G-force maneuver that might cause the hub units to flex and knock the pistons back, the system will send pressure to the caliper to push the pads back into the correct position. This is designed to prevent a long pedal on the next stop. Within the torque specs for the LX platform, a stand out number is the 110 ft.-lbs of wheel torque.
The biggest complaint from technicians is the difficulty seeing the pads through the inspection holes and edges of the caliper. Chrysler recommends technicians compress the piston enough so that the lower caliper bolt can be removed and the caliper can be rotated upward.
In the rear, the upper bolt can be removed and the caliper can be swung down.
Why should you go through this trouble? On dual-piston calipers, tapered brake pad wear can indicate problems with the caliper seals or the hardware. Also, it is easier and more profitable to know if the calipers need to be replaced during the estimate process than needing to call the customer a second time and wait for the part.
Chrysler set the total disc thickness variation and runout standards very high for all the brake packages. Disc thickness should not vary more than .0004” (.010mm) and total runout should not exceed 0.0014” (.035mm). These are some of the lowest numbers in the industry, and even forgetting to properly clean the hub’s flange can put a vehicle out of specification.
Only one recall or TSB has been issued for the rear-wheel drive LX platform’s brake system. Forty-five thousand LXs with a 2.7-liter were recalled due to a brake line under the hood that was mounted too close to the EGR valve’s tubing.
Installing New Pads and Rotors
Installation of new pads and rotors is straightforward. It’s recommended that abutment clips be replaced with every pad change. If the clips don’t have the right amount of tension, the retraction of the pistons will not reduce brake drag. This could mean decreased gas mileage.
The front brake caliper bracket should be tightened to 70 ft.-lbs and the rear should be tightened to 85 ft.-lbs. The caliper bolts have a torque spec of 44 ft.-lbs and 23 ft.-lbs in the rear.
Base System Bleeding
Pressure bleeding is highly recommended to bleed this brake system to ensure all of the air is removed from the system. Manual bleeding may also be used, but additional time will be needed to remove all the air from the system. The bleeding pattern goes: right-rear, left-rear, right-front and finish at the left-front.
Chrysler advises to open the bleeder screw at least one full turn. Some air may be trapped in the brake lines or valves far upstream — as far as 10 feet or more from the bleeder screw. If the bleeder screw is not opened sufficiently, fluid flow is restricted causing a slow, weak fluid discharge.
Brake systems with ABS must be bled as two independent braking systems. The non-ABS portion of these ABS brake systems is to be bled the same as any non-ABS system. The ABS portion of the brake system must be bled separately.
To ensure all of the air is bled from the ICU or junction block quickly, raise the rear of the vehicle approximately 10-12 inches as measured at the rear bumper and use a scan tool with bi-directional control of the ICU.
Parking Brake Adjustment
The adjustment of the parking brake is simple and easy to access. Most adjustments can be made at the wheels.
1. Remove the rear brake rotor.
2. Using a brake shoe gauge, measure the inside diameter of the parking brake drum portion of the rotor.
3. Place the gauge over the parking brake shoes at the widest point.
4. Using the adjuster star wheel, adjust the parking brake shoes until the linings on both parking brake shoes just touch the jaws on the gauge.
5. Install the rear brake rotor.
6. Perform fine adjustment of parking brake shoes.
1. Place the parking brake lever in the full released position.
2. Raise and support the vehicle.
3. Remove the plug in the parking brake shoe support to access the adjuster star-wheel; rotate the adjuster star wheel in the following direction to expand the shoes outward against the drum.
• Left brake — Rotate the star-wheel toward the rear of vehicle.
• Right brake — Rotate the star-wheel toward the front of vehicle.
4. Turn the adjuster star-wheel until the wheel will not rotate (dead lock).
5. Back off the adjuster six detents (teeth).
6. Rotate the wheel, checking for light drag. If drag is too heavy, continue to back off the adjuster one detent at a time until light drag is present. Do not back off the star-wheel more than 17 detents from wheel lock.
7. Install access plug.
8. Adjust opposite wheel parking brake shoes using the same method.
9. Apply and release the parking brake lever once to ensure the proper operation of parking brakes.