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Motoring Q&A: Resolving brake rotor warping issues

Question: I have a 2005 Jeep Grand Cherokee with 160,000 miles on it. The problem is with the brake rotors warping. Every time I've had the brakes worked on, they start to pulsate again after a few thousand miles. Last time, the dealer installed new pads and rotors, but the same thing happened. Are there certain types of rotors or pads I can use to prevent this?

Question:

I have a 2005 Jeep Grand Cherokee with 160,000 miles on it. The problem is with the brake rotors warping. Every time I've had the brakes worked on, they start to pulsate again after a few thousand miles. Last time, the dealer installed new pads and rotors, but the same thing happened. Are there certain types of rotors or pads I can use to prevent this?

Answer: First, let's review the primary causes of brake rotor warping - excessive heat or manufacturing defect. Seems unlikely you and the many other Jeep owners who've complained about the same problem would continually get faulty replacement rotors.

Thus, focus on excess heat. If a driver consistently brakes late and hard for stops or drags the brakes while driving, the heat buildup in the rotors can eventually cause distortion, uneven wear, and warpage. Always brake early and brake lightly whenever possible. And here's a little tip. Once stopped for a light, let the car roll a foot or so forward to move the pads off the "hot spot" on the rotor. During a long stop, do this a couple of times - safely, of course. This reduces "heat soak" in the rotors, where one section is significantly hotter than the rest of the rotor.

Design, manufacturing, and mechanical issues can certainly contribute to warped rotors. Undersize calipers and rotors may not be able to dissipate heat fast enough during aggressive braking to prevent eventual warpage. Better-quality replacement rotors and pads may help this type of issue. If a mechanical or hydraulic issue is preventing the brake proportioning valve or rear brakes from doing their share, the front brakes can be overworked and overheated in "normal" driving.

Sticky caliper pistons and/or binding caliper slider pins are a primary cause of rotor warpage and uneven rotor wear. An often overlooked cause for warped rotors is improper or uneven torque on the wheel lugs. Always - every single time - make sure the wheels are tightened in a symmetrical order in stages to the proper torque specification. Similarly, rust or corrosion between the hub face and rotor can lead to uneven brake wear.

Proper rotor and pad "bedding" or break-in when new can significantly affect brake performance and life expectancy. Here's how I do it: Find a lightly traveled 45- to 50-m.p.h. road. With no vehicles behind you, accelerate up to 45 m.p.h., then brake very firmly down to rolling speed. Repeat this a few times until you smell the tinge of brake heat or feel the beginning of brake fade. Then just cruise along at the speed limit, allowing the brakes to cool back to normal temperature. This process "beds" the brakes, making the pad and rotor surfaces "happy" with each other. Once properly bedded, the brakes should perform well for their full service life.

Q: My daughter and her husband bought a 2006 Nissan 350Z. No problems with it, but a headlight quit working. The Nissan dealer wants $1,300 to replace it. This seems sort of excessive.

A: According to my ALLDATA automotive database, this Nissan is fitted with xenon HID headlamps. Nissan service bulletin NTB10-061A dated June 2010 suggests that a failed headlamp bulb, about $180, or HID control unit, $400-$500, is the most likely cause of an inoperative headlight. Even with an hour or so of labor, that's a far cry from $1,300 to replace the entire headlight assembly.