Choosing/Installing New Brake Rotors and Pads

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By Jim Bigley - www.TheDieselPage.com



The front and rear brake rotors and pads were recently replaced on my 2001 GMC 2500HD, not due to wearing out, but due to rusting caused primarily by the magnesium chloride road de-icer (essentially a salt) used on the highways during the winter here in Montana. The above photo shows what the rear rotors looked like soon after removed from the truck and then sitting overnight after a light rain. You can also see how the brake pads had lost contact with large areas of the rotors. It was well past time to replace these parts. Read on for a few ideas that could make your brake project a little easier.

What follows is not a step by step replacement, but rather a "heads up" concerning what to look for, how I did the work and what parts I used.




These brake pads illustrate what caused me to do this project now... The outer pad was at about 50% wear, while the inner pad was producing metal on metal. What happens is this... the road de-icer reduces the contact area between the pad and the rotor. This smaller braking surface wears faster, and in the time it takes for that smaller contact patch to wear away, the rest of the rotor becomes grossly rusted. This rough rusted area then rapidly wears away the pad's brake material, resulting in metal on metal.



Once the brake caliper has been removed, use wire to secure the assembly to the frame or spring pack (the front caliper should be secured to the upper A-arm). Don't allow the heavy brake caliper to hang on the brake line.



Incidentally, the front calipers are mounted using caliper guide pin bolts having a 15mm bolt head. The rear calipers are mounted using guide-pin bolts that require a T55 bit. This is the bit I used. Bought it at NAPA. I used an adapter in this bit so I could use an end wrench to loosen/tighten. There's not a lot of room for a lengthy flex-handle.



Rusted brake rotors can sometimes be tough to remove from the hubs. Luckily, factory GM rotors (and these NAPA replacements) used on the front accept bolts that can be used to force the rotor off the hub. We used common 3/8" SAE hardware store bolts, which seemed to fit the threaded holes perfectly. The 3/8" bolts worked great to force the rotors off the front hubs.



You can use a couple of bolts/nuts/washers to push the rear rotors off the hubs using the caliper mounting bracket attachments on the rear hubs. This works great. Don't use a big hammer to knock the rotors off. Heavy impact can peen the bearings/races, causing a premature wheel bearing failure.



Caliper Mounting Bracket Bolts, Front/Rear (25/35 series): 221 lb-ft (21mm socket): Reaching these torque values will require some effort to loosen, then re-assemble. For tools, you'll need 1/2" drive 6-point 21-mm socket (preferably an impact socket), a long flex-handle and a torque wrench capable of handling 221 lb-ft of torque (it may require ~300 lb-ft of torque to break them loose). It's all about leverage, so a longer flex-handle and torque wrench will make it easier for you. The caliper bracket bolts (having a 21mm hex head) were originally installed using a thread locker. The thread locker is usually persistent enough that you shouldn't need to re-apply new thread locker when re-installing the hardware, but a re-application of the "blue" thread locker is up to you. I needed to use a cheater pipe on my 1/2" flex-handle, and I considered it a tossup whether my new 1/2" drive 6-point 21mm NAPA socket could loosen those bolts without breaking, but it survived. You won't need any deep-well sockets for this job.

An air impact capable of at least 300 lb-ft of torque could be used with wobble extensions, but it's difficult to get a square shot at the bolt heads due to interference with the suspension components.

Note: I also have a big 3 feet long 3/4" drive flex-handle that I bought a couple of years ago to remove the Duramax damper bolt. That long 3/4" flex-handle would have made it easier to break those caliper bracket bolts loose due to its length/leverage advantage... but I didn't have a 3/4" drive 21mm impact socket. Note to self...

Before installing the new rotor you should use an air nozzle to blow out the dust in/around the e-brake parts. I then applied a little oil to a few of the rusty components to help them survive the coming winters. Always make sure to keep oil away from the actual brake components - shoes/pads/drums/rotors/braking surfaces.




You'll need to use brake cleaner to remove the protective film from the wear surfaces of the new rotors. BTW - I did knock off the loose rust and flaking paint from these calipers/brackets. That was followed by a light coat of oil (used as a rust preventive) - keeping it off the new pads and rotors, obviously. This'll need to be re-applied on a yearly basis. Another alternative it to strip/clean/paint or replace the calipers/brackets. It's up to you. And, I re-lubed the caliper guide pins using NAPA caliper grease. This special grease was designed for the high temperatures commonly seen in brake calipers. You can see in the above photo how the rust preventive I've been using has protected the areas I've applied the solution to (frame/spring pack). More info on this solution can be found below.



These are the front/rear rotors I used for this project. These "made in the USA" rotors appear to be well made, and are coated in all areas other than the areas where the pads make contact. So... they'll still rust on the wear surfaces...



Rear brake pads part #PF-7653M

Continued next post...


Jim