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Nuts & Bolts: Warped Rotor Myth

Posted in How To: Tech Qa on August 20, 2018
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Photographers: Trenton McGee

I have a 2003 GMC 3500 single-wheel truck that I use to haul a pretty big toy hauler. I’ve weighed the whole thing and it’s heavy, but I’m within the weight rating of the truck. I live up in the mountains in Colorado, and I keep going through brakes on the truck. I’ve tried several different brands and quality levels of brake pads, but I’ve warped multiple sets of rotors. I consider myself a conservative driver, and I even downshift on the grades to use engine braking, but it doesn’t seem to help. I get that I’m probably right at the edge of what the brake system was designed to do and can expect to be replacing brakes more often than a flatlander, but it gets really expensive when you’re replacing them every year and after practically every big trip. Is there an upgraded rotor or even a better brake system available for my truck?

Mark F.
Via nuts@4wor.com

We were recently schooled on warped rotors from some friends over at Baer Brakes (baer.com). First off, it’s exceedingly rare to actually warp a rotor. Instead, the cause of the shudder you feel through the pedal is an uneven buildup of brake pad material on the rotor itself.

Here’s how it works. Modern asbestos-free and nonmetallic brake pads contain different resins in addition to the actual brake material itself. Some of these resins and materials transfer themselves to the rotor face so that there will be adherent (sticky) braking in addition to abrasive braking. In a nutshell, when a brake system is properly bedded in, there’s a thin layer of pad material on the rotors. When you use the brakes hard, such as when coming down a steep grade, the heat buildup causes these resins to loosen. When you stop the vehicle completely, such as at a red light at the bottom of an off-ramp after that steep hill, you actually make an imprint of the brake pad on the rotor, creating a high spot. By the time you get gas or stop for lunch (or whatever) the rotors have had a chance to cool off, but that high spot is still there. As little as 0.0004 inch can be felt through the pedal, and 0.001 inch can be downright annoying. Repeated use just leaves more material on the high spots, making the shudder worse.

Now that you understand what’s going on, here’s what you can do to help combat it. If caught early, you can often eliminate the shudder by rebedding the brakes. To do this, find a safe area where you can make a series of hard slowdowns from 50 mph to about 10 mph. Don’t come to a full stop. Doing this several times will heat up the material on the rotors and help smear it evenly on the face of the rotors again. Then drive around for a little while without stopping much to let the brakes cool off.

Another thing you can do is avoid being on the brakes with the vehicle stopped when you know the brakes are hot. Shift it into Park while you wait for the light to turn at the bottom of the off ramp and take your foot off the brakes. This helps avoid leaving a footprint of the pad on the rotor.

Buy the best-quality brake pads you can afford and stick with reputable name brands if possible. For heavy applications such as yours, a semimetallic pad is a good choice because they rely more on abrasive braking than adherent braking, and they have a higher maximum operating temperature. When necessary, don’t skimp on replacement rotors even though it might hurt. There are also some bolt-on aftermarket upgrades out there for your truck that don’t require wheel changes. EBC Brakes (ebcbrakes.com) offers both pads and rotors for your truck.

Lastly, you might consider doing what you can to supplement the factory brake system by making sure the brake system on the toy hauler is in tiptop shape. If you have a diesel, it might not be a bad idea to install an exhaust brake on the truck. Several versions are available in the aftermarket, and they substantially improve overall braking performance, not to mention taking a lot of strain off of the stock brakes.

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