2005-2008 Pontiac Grand Prix Front vs Rear Brakes: What Wears First and What to Replace

By Core Brake Parts Tech Team — Circleville, OH warehouse

On a 2005-2008 Pontiac Grand Prix the front brakes almost always wear out first, and the rears typically outlast them. Every Grand Prix of this generation has disc brakes at all four wheels, so a full brake job means two different pad and rotor sets, and GM says linings should always be replaced as complete axle sets. Here is how to tell which end needs work and what to replace together.

How the Grand Prix brake system is laid out

The 2005-2008 Grand Prix is a front-wheel-drive sedan with power-assisted four-wheel disc brakes and ABS. A GM fleet specification sheet for the 2006 Grand Prix sedan with the 3.8L 3800 Series III V6 lists 4-wheel disc brakes with Electronic Brake Force Distribution, an 11.7-inch front rotor and a 10.5-inch rear rotor. That size difference tells you a lot: the front rotors are bigger because they do most of the stopping.

The owner's manual explains that the hydraulic system is split into two parts, so if one part fails the other can still stop the car. The parking brake is a foot pedal to the left of the brake pedal, not an electronic parking brake, so no scan tool is needed to service the rear calipers.

The 5.3L V8 GXP uses its own brake parts, which is why V8-specific pads such as the EBC Redstuff ceramic front pad set for the Grand Prix 5.3L are listed separately from V6 parts. Always confirm your engine before ordering.

Why the front brakes wear first

When you brake, weight shifts forward onto the front tires. The front brakes get the grip, so they are sized to do most of the work, and they wear faster. On a nose-heavy front-drive sedan like the Grand Prix, where the engine and transaxle sit over the front wheels, that bias is even stronger.

Electronic Brake Force Distribution adjusts how much pressure goes to the rear as load changes, which keeps the rears from locking but also means they stay lightly used in normal driving. Most owners do more than one front brake job for every rear job, though stop-and-go city driving, heavy loads or a heavy right foot will shorten the life of both.

The rears are not maintenance-free. Rear pads can wear fast if a caliper slide pin seizes or the parking brake cable sticks and drags. That is why you should inspect both ends every time the tires come off.

Symptoms: is it the front or the rear?

• High-pitched squeal while driving that stops when you brake firmly: the owner's manual describes exactly this as the built-in wear indicator on the disc pads. The sound can come and go or be constant. Find which wheel it comes from and have the pads replaced.
• Vibration in the steering wheel when braking: usually front rotor thickness variation. GM notes that properly torqued wheel nuts help prevent brake pulsation, so uneven lug torque from a previous tire job is a common cause.
• Pulsation felt in the seat or pedal but not the wheel: points more toward the rear rotors.
• Grinding metal-on-metal: pads are gone and the rotor is being cut. Replace the rotors on that axle too.
• Car pulls to one side: a sticking front caliper or collapsed hose on one side.
• One rear wheel much hotter than the other after a drive: a dragging rear caliper or parking brake.
• Light squeal on the first few gentle stops on a damp morning: the manual says this can be normal and does not by itself mean something is wrong.

Warning lights matter too. The brake system warning light should come on briefly at startup. If it stays on, check the fluid level first, since worn pads let the level drop as the caliper pistons move out. The driver information center also shows a Low Brake Fluid message. A sudden large drop in fluid means a leak, not wear.

What to replace, and what to replace together

GM's owner's manual is direct: brake linings should always be replaced as complete axle sets. That means both front wheels at once, or both rears at once, never one side.

Front brake job

• Front pads (both sides), from our brake pad collection or ceramic brake pads for low dust.
• Front rotors if they are below the minimum thickness cast into the rotor, scored, heat-spotted or warped. New brake rotors are usually the better choice over machining thin ones.
• New abutment clips and slide pin boots from a brake hardware kit. Old rusted clips cause noise and uneven wear.

Rear brake job

• Rear pads and rotors as an axle set.
• Clean and lubricate the rear caliper slides and check that the parking brake releases fully.
• A replacement caliper if the piston is seized or the boot is torn.

Doing all four at once

If the fronts are due and the rears are at half life or less, many owners do both ends in one weekend to buy parts once. A matched front and rear pad and rotor kit is the simplest way to do that. If the rears still have plenty of material, leave them and inspect them at the next tire rotation.

Brake fluid and parts quality

The owner's manual specifies DOT 3 brake fluid only, from a new sealed container. Clean the reservoir cap before you open it, and never let engine oil or any mineral-based fluid near the system, because it damages brake system parts. Old fluid absorbs moisture, so a flush during a full brake job is cheap insurance.

GM also warns that the wrong replacement parts can change the balance between the front and rear brakes. Buy pads and rotors listed for your exact year and engine rather than guessing, especially if your car is a GXP.

How hard is the job?

A front pad and rotor job on the Grand Prix is a reasonable driveway project for someone with a floor jack, jack stands, a socket set and a torque wrench. Rears are similar, with the extra step of making sure the parking brake is fully released before you pull the caliper. The disc brakes adjust for wear every time you apply the brakes, so no manual adjustment is needed afterward.

Torque caliper bolts and lug nuts to the values in the factory service manual, tighten lug nuts in a star pattern, pump the pedal until it is firm before moving the car, and bed in the new pads with a series of moderate stops. The manual also says to see a professional if the pedal does not return to normal height or pedal travel increases quickly.

Frequently Asked Questions

Does the 2005-2008 Pontiac Grand Prix have rear drum brakes?

No. GM's specification for this generation lists four-wheel disc brakes, so the rear uses pads and rotors, not shoes and drums.

Can I replace just the front brakes?

Yes. Front and rear wear at different rates, so it is normal to replace only the front axle set. Just replace both front sides together, as GM recommends.

Are GXP brake parts the same as V6 Grand Prix parts?

No. The 5.3L V8 GXP uses its own brake components, so pads and rotors for the V6 are not a match. Check that the listing names your engine.

What brake fluid does a Grand Prix use?

The owner's manual calls for DOT 3 brake fluid from a new sealed container.

Why do my brakes squeal only when I am not pressing the pedal?

That is the classic sound of the built-in pad wear indicator. It often goes quiet under firm braking. Have the pads checked and replaced soon.

Should I replace rotors every time I replace pads?

Not always, but it is common. Replace rotors if they are under minimum thickness, grooved, cracked or causing pulsation. New pads on a worn rotor tend to wear fast and make noise.

Sources

1. 2008 Pontiac Grand Prix Owner's Manual - Brake Wear - wear indicator sound, axle-set replacement, wheel nut torque and pulsation
2. 2008 Pontiac Grand Prix Owner's Manual - Brake Pedal Travel and Replacing Brake Parts - self-adjusting brakes, pedal travel warning, front/rear balance
3. 2008 Pontiac Grand Prix Owner's Manual - Brake Fluid - DOT 3 fluid from a sealed container
4. 2008 Pontiac Grand Prix Owner's Manual - Brake System Warning Light - split hydraulic system and warning light behavior
5. 2008 Pontiac Grand Prix Owner's Manual - Parking Brake - foot-pedal parking brake
6. State of New Jersey fleet contract spec sheet, 2006 Pontiac Grand Prix sedan - 4-wheel disc with EBD, 11.7 in front and 10.5 in rear rotors, 3.8L V6