2002-2006 Infiniti Q45 Front vs Rear Brakes: What Wears First and What to Replace

By Core Brake Parts Tech Team — Circleville, OH warehouse

On a 2002-2006 Infiniti Q45, the front brakes wear first. The front axle does most of the stopping work on every stop, so front pads and rotors usually need service before the rears, often by a full pad set or more. The rear discs still wear, and the Q45 adds a small drum-style parking brake inside each rear rotor that is easy to forget.

How the Q45 brake system is laid out

Infiniti's press material for the third-generation Q45 lists 4-wheel vented disc brakes with 4-wheel ABS, Brake Assist (BA) and Electronic Brake force Distribution (EBD). That means there are no drum service brakes on this car: all four corners use a caliper, a pair of pads and a vented rotor. The car is front-engine and rear-wheel drive, powered by a 4.5-liter V8, so there is a heavy engine sitting right over the front axle.

Three electronic systems decide how hard each corner works:

• EBD - Infiniti describes it as controlling front and rear brake distribution depending on load, meaning passengers and cargo. With a full back seat and trunk, the rears are allowed to do more. Driving alone, the system keeps more of the work up front.
• Brake Assist - senses a hard or panic pedal application and helps build full braking pressure. On cars with Intelligent Cruise Control, Infiniti added a preview function that pre-pressurizes the system when the sensors see a sudden slowdown ahead.
• Vehicle Dynamic Control (VDC) - can brake individual wheels and reduce engine output to correct understeer or oversteer. It is standard on every Q45 of this generation.

The parking brake is separate from the rear pads. The factory parts catalog lists a parking brake shoe set for the 2002-2006 Q45 (current Infiniti part number 44060-AR06K, which replaced 44060-AR025). Those shoes sit in the drum-shaped center section of each rear rotor, often called a drum-in-hat design.

Why the fronts wear first on this car

When any car slows down, its weight shifts forward. The front tires get pressed harder into the road and can put more braking force down, while the rear tires get lighter. Engineers size the brakes and set the brake balance to match, so the front pads and rotors handle the larger share of the work on every stop. EBD then trims rear pressure so the rear wheels do not lock up as they unload.

The Q45 adds a few things that push even more wear to the front:

• Nose-heavy layout. A big V8 over the front axle loads the fronts before you even touch the pedal.
• Driving alone. Because EBD reads load, a car that usually carries one person keeps its rears working less, and the front-to-rear wear gap grows.
• Power and weight. The 340-hp V8 gets a large luxury sedan up to speed quickly. Every bit of that speed has to come back out as heat, mostly at the front rotors.
• Stop-and-go and Intelligent Cruise. Cruise control that uses the brakes to hold a following distance adds many light applications in traffic.

The rears are not immune. VDC and traction control apply individual brakes on slippery roads, and a sticking rear caliper or a parking brake that does not fully release will chew through rear pads fast. That is why you still need to measure all four corners at every tire rotation.

Front vs rear: what to expect

Treat the table as a pattern, not a schedule. Real wear depends on how and where you drive, so always go by measured pad thickness and rotor condition, not mileage.

Symptoms and how to tell which end is worn

Front wear signs: a high-pitched squeal from the wear indicator, a pulsing pedal or a shimmy in the steering wheel when stopping from highway speed, and a car that pulls to one side under braking. Pulsation you feel in the steering wheel almost always points to the front rotors.

Rear wear signs: a grinding or scraping noise from the back, pulsation felt in the seat or pedal but not the steering wheel, and a parking brake that needs more clicks to hold or will not hold on a hill.

Quick check: with the wheels off, look at the pad material through the caliper window on both axles and check the inner pads too, since inner pads often wear faster than outer ones. Look for a lip at the outer edge of each rotor, blue heat spots, or deep grooves. A rotor with a noticeable lip or scoring should be replaced or measured against the minimum thickness cast into the rotor or listed in the factory service manual.

If the ABS, VDC or brake warning light is on, have the codes read before you buy parts. On these systems a bad wheel speed sensor or low fluid can trigger warnings that have nothing to do with pad wear.

What to replace, and what to replace at the same time

Front brake job: replace pads and rotors as a pair across the axle, never one side. We carry front drilled and slotted rotors made for the 2002-2006 Q45 4.5L, and you can pair them with pads from our ceramic brake pads collection. Ceramic compounds tend to run quieter with less dust, which suits a luxury sedan. Use new clips and shims from our brake hardware kits, because worn anti-rattle clips are a common cause of noise on otherwise new brakes.

Rear brake job: the same rule applies - pads and rotors as an axle set from our brake pads and brake rotors collections. Because the rotor comes off, it is the right moment to inspect the parking brake shoes. If the lining is thin, glazed or contaminated with grease or fluid, replace the shoe set and its hardware while everything is apart, then adjust the parking brake as the service manual describes.

At the same time, on either end:

• Check caliper slide pins for free movement and re-lubricate them with a brake-specific grease. A stuck slide is the top reason one pad wears far faster than the other. Replace seized units from our brake calipers collection.
• Inspect the rubber brake hoses for cracks and bulges; replacements are in brake hoses.
• Look at the brake fluid. Use only the fluid type printed on the master cylinder cap or listed in the owner's manual, and flush it if it is dark or overdue.

How hard is the job?

A front or rear pad and rotor job on the Q45 is a reasonable driveway job for someone with a jack, stands, a torque wrench and basic hand tools. Tighten caliper bracket bolts and lug nuts to the values in the factory service manual, and bed in new pads with a series of moderate stops before normal driving. Rear jobs take a little longer because the parking brake must be backed off before the rotor will come off, and the shoes need adjusting afterward.

Two things are worth handing to a shop if you are not set up for them: bleeding the brakes on an ABS and VDC-equipped car, and diagnosing any warning light. Also note that the 2004 Q45 was covered by NHTSA recall 04V497000 for a brake lamp switch that could keep the brake lights from coming on. If your brake lights act up, run your VIN through the NHTSA or Infiniti recall lookup first.

Frequently Asked Questions

Does the 2002-2006 Infiniti Q45 have rear drum brakes?

No. The service brakes are vented discs at all four wheels. The only drum-style part is the small parking brake that uses shoes inside the center of each rear rotor.

Should I replace front and rear brakes at the same time on a Q45?

Only if both are worn. The fronts usually need service first. Replace by axle, and measure the rears each time so you know how much life they have left.

Why are my rear pads wearing faster than my fronts?

That is not normal for this car. Look for a sticking rear caliper or slide pin, a parking brake that is not fully releasing, or a brake that is dragging. Fix the cause before installing new pads.

Do I need new rotors with new pads?

Replace rotors if they are below minimum thickness, warped, heat-spotted, or deeply grooved. Putting new pads on damaged rotors leads to noise, pulsation and short pad life.

Why does my Q45 shake when I brake from highway speed?

A shake in the steering wheel usually means uneven front rotor thickness or pad deposits. Check the front rotors first, then the rears if the shake is felt mostly in the seat.

Sources

1. Infiniti USA Newsroom - 2003 Q45 Press Kit At A Glance - 4-wheel vented discs with ABS, Brake Assist and EBD
2. Infiniti USA Newsroom - 2003 Q45 Press Kit - EBD varies front/rear distribution by load; VDC standard
3. Infiniti USA Newsroom - 2006 Q45 Press Kit - Brake Assist preview function with Intelligent Cruise Control
4. Consumer Guide - 2002-06 Infiniti Q45 - rear-wheel drive, 4.5L 340-hp V8, antilock four-wheel discs, 2004 brake light switch issue
5. Infiniti Parts Deal - Q45 Parking Brake Shoe - parking brake shoe set 44060-AR06K fits 2002-2006 Q45
6. NHTSA Recalls - 2004 Infiniti Q45 - recall 04V497000, brake lamp switch