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Replacing Brake Pads & Rotors


Well I finished my brake job this weekend without too much strife. A couple points from my experience maybe helpful to others:

I removed my rear calipers to work on... (working on them while still connected to the hydralic lines, looked like a receipt for impatience and serious damage).

I detached both rear halfshafts (I had to put camlock washers on anyway) So I really had no access problems with the yoke bolts. Also since these haven't been touched since factory installation there was no thread lock from hell on these bolts, and they came out easily (unlike the fronts). I used Locktite 242 when I replaced them... I figure 271/272 is overkill, and I don't like the thought of using a torch on my brake calipers to release the locktite next time I do this job.

I backed off the rear pistons using a block of wood and a wheel puller, in concert with a "slip and lock nut" wrench used for plumbing (this is a parallel jaw wrench, with thin jaws). This wrench was just about perfect, and cheap ($9.00 piece of junk from Sears), grinding the jaw tips would make it a bit better (but I didn't do this). I could actually press the piston and turn the monster piston nut (approaching 2 1/2"!) at the same time--although once the piston moved initially I could compress it just using the wrench and thumb pressure. I also screwed a piece of tubing into the hydralic fitting to keep things neat while the fluid was forced out, and used rubber caps to cover open brake lines.

I applied lite amounts of silicone grease to the yoke guide pins and the pad guide rails (thanks Chuck, good tip).

I used the Rancho brake pads which I think I'll like... But the pad sets include TWO DIFFERENT TYPES OF PADS, and there was no indication of this in the included sheet... This cost me re-doing one caliper 'cause I didn't notice it at first. (R. Thomas... would you address this with Rancho?) So either this was a mistake on Ranchos part (both sets had differing pad types), or intended, as I assumed. One pad is indentical in shape to stock pads and the other is perhaps %20 larger, but fits in the caliper opening just fine... Since the piston side pad often wears faster I put the bigger pad on that side (hmmm, maybe the differing pads eliminate pad resonance, and hence the dreaded brake vibration/chatter... sounds plausible, no?). At any rate with too few miles on the new pads I believe that they'll work significantly better than stock pads, and so far I've had no brake chatter... But I'll need to get a few hundred more miles on these brakes before the jury's in...

Finally after conscripting my neighbor I (we) performed a non-eventful bleed, and now I'm set for at least another 24K... Oh and it didn't cost me the $1500.00 the dealer wanted (The $500.00 others have said dealers are asking, is probably not unreasonable though, it is a big job).

Keri & Lucy (94 diesel open-top)

After wrestling with the front caliper, with the fear that I would round the bolt off I took drastic measures. I took a Craftsman 14MM wrench, took a torch to it and bent it (I know in most states this is illegal, but hey, I was desperate, besides I was feeling like Mcgyver). Then I took a trip to the temple of Sears to confess my sins, and beg forgiveness for desecrating a tool. Salvation was found in what looks like a miniature breaker bar for a 1/4" drive socket (sorry, too many Christmas specials).

Anyway, you were right about the locktight red. I took my little Benzamatic Kit which is a propane and Oxygen combo you can get for around $45.00, and heated that little caliper bolt, and used my new mini breaker bar and 14MM socket, and it came right out. I like the Propane Oxygen combo because you can get a hot flame, and really pinpoint it instead of napalming the entire caliper. Another suggestion, in addition to a very informative article on the homepage, would be to tie the caliper up with wire which will relieve some of the stress on the brakeline and keeps it out of the way if you need to remove the rotor. Once the upper and lower caliper bolts were removed and the brake cylinder was pressed back, I greased the contact points and the rest was a cakewalk.

In addition, I had to remove a rotor which was badly scored. That was even easier. One thing you may want to remember, though, tie up the halfshaft before you remove the four bolts which go through the rotor. I took a piece of chain and put a bolt with some washers and a nut through some links so that I could lower the halfshaft slowly and far enough to slip the rotor off, and stick the bolt back through the links when it was clear. That halfshaft is heavy, especially if it's lying on your chest, and when your trying to line the holes up with the rotor to bolt it back on, it has to be perfectly aligned, so chaining it up frees up your hands to maneuver the rotor, which isn't light either.

All said and done, with the right tools, the Hummer's brake pad and rotor replacement is probably the easiest vehicle I have worked on. I think the lock tight on the caliper bolts is an excellent idea. By the way, for those on the east cost (I'm not sure how far the retail chain extends), Pep Boys Auto Parts, if they have a service facility will resurface rotors for $5.00 plus tax. You will probably have to provide the specs (by the way, does anyone know the minimum specs on rotors?), but it's quite a deal. Including my new tool the and resurface one rotor, the job cost less than $80.00.

By the way, thanks to all for the info. I hope you find some of this info helpful.

I have changed brake pads quite a few times on cars. It sounds like from the HML article it is a lot harder than one would think. Is the opinion that should try I m mself or get someone to do it for me.

I, too, was daunted by the descriptions on the HML. Mostly, this was because I had never done *disk* brakes before. I was surprised at how easy it was. The second (rear) brake took me only about 30 min. start to finish. (First one was longer, but I didn't know the part that I am sharing now.)

The only tricky part about the Hummer brakes is compressing the rear pistons. The piston must be turned while it is pushed in. There is a tool to do this, but I am still trying to find one for under $200. (I have some leads, but no tool yet.) There are several methods that can be used without the special tool. Most popular seems to be turning piston with a large pair of "channel-lock" type pliers. An alternative tool for turning might be a plumbers spanner. Pressing the piston in can be accomplished by using a large C-clamp, or similar device. It can also be done by a conventional piston retraction tool. You turn, then you push in, then you turn, then you push in, etc.

The fronts are easier - no turning of the piston required.

Access to the bolts is a little tight, but it is managable. I would recommend you try them yourself.

Dave Breggin

I too have never done brakes on the Hummer but I am sure that I will soon. What is the reason for having to turn the piston while you push it in? Do you have to turn it any special amount? or is it just to keep it from binding while it is pushed in? Thanks again!


The reason for turning the piston is to release some sort of ratchet in the parking brake part. If you do not turn it, it will not compress. Turning alone will not compress either. It takes both. BTW, I turned both of mine clockwise. I would turn them about 1/2 turn or so, then press the piston in until it gets firm, then repeat.

The piston is hex-shaped on the outside to allow it to be turned. I forget the exact dimension, but it is about 2-1/2" across.

Dave Breggin

I finally finished the brake job I have been talking about. Total time front 40 min, rear 110 minutes. The NAPA AE-7122A pads are just fine. No squeak or rattle. I suggest the brake lines be removed in the rear since there isn't any rubber section for flexibility and it is very easy to break one off. You definitely need a c-clamp to compress the rear pistons and a big wrench to turn that big nut. I had 36565 mile on the original set and there was about 10-20% left on the pads. Some were more worn than others. The original pads are bonded and the NAPA ones are riveted. I don't know which is supposed to be better, but the NAPA's are lifetime warranty. If anyone knows what vehicle those pads are supposed to be for let me know. Then maybe a parts store could cross-ref to other brands.

I had my Hummer (95 diesel wagon) serviced at New Dimensions last Tuesday

During the service their technician noticed a few things needing attention including worn brake pads on the rear. So with the recent postings regarding brake pad changes I decided to go for it.

I provided my local parts store with the PN's from the Hummer Knowledge Base and asked them to get me 2 sets. Their preferred brand is Ferodo (Federal Mogul) the part number for the Hummer is SQD203. This PN includes pin lubricant and anti rattle shims. Cost 37.95 per axle. These pads have a lot of metal in them so you probably want to handle them with gloves. I used some thick latex gloves I got at Home Depot. I also picked up some DOT 5 brake fluid.

Rear axle:
I removed the under body protection which dramatically increases the working room. Remove the parking brake cotter pin, clevis and snap ring that holds the cable housing to the caliper assembly. Remove the 2 9/16" cap screws that attaches the yoke to the differential.

You can now remove the caliper/yoke assembly and take out the pads.

Here is a question for the list, has anyone been able to screw and compress the rear caliper pistons on the truck? I removed the brake line from the caliper 3/8" tubing wrench. I compressed the piston using a large pair of channel locks and pushing the piston against a large socket. Be careful not to damage the piston dust boot while compressing. This is kind of messy, I used an old dish to catch the brake fluid and there is a lot. I then cleaned up the yoke pins and lubricated them.

Reassembly is much easier than taking it apart. Even after thinking about it, reading the warning, and visualizing the reassembly I still tried to put the pads in with the metal facing the rotor. Be sure to put the larger pad on the side with the piston. Bleed the brakes and readjust the parking brake and the rears are done.

The front:
I think Michael recently posted his experiences with the left front brake. There has to be a special place in Dante's inferno for the person who put the upper bolt into the caliper. It took about 20 minutes to get the stiff bolt out of the hole. The right side went without a hitch.

Before compressing the front pistons (I didn't remove the calipers) be sure to remove some of the fluid from the rear reservoir in the master cylinder.

Reassembly went much quicker than disassembly.

Observations and notes.
Don't even think about doing the job without removing the underbody protection. Be sure to clean the yoke pins and lightly lubricate them. I used medium locktite on the caliper bolts. When I removed the cover to the master cylinder I noticed the rear reservoir (front brakes) fluid was colored kind of yellow. The front reservoir had the bluish purple color of DOT 5 fluid. It would appear during a service someone put DOT 3 fluid into the reservoir. This stuff is not compatible. I completely flushed the brake system with new fluid after this discovery. I used a clear plastic bottle to catch the fluid in during the bleeding process. The DOT 3 and DOT 5 fluids even have a different specific gravity. The DOT 3 stuff sank to the bottom of the bottle. The colors were very different. Not too bad of a job with some determination and patience. Total cost about $125 with brake fluid. 4 Hours of time.


Well, I did my brakes yesterday. I started around 12pm and finished just after 9pm. The fronts took me an hour to do both of them. They were a breeze. The top bolts aren't easy to see, but I found that by lying on my back under the caliper I could reach up and get a 9/16" box wrench onto them by feel. I broke the top bolts loose by putting a long 1" box wrench over the end of the 9/16" so it hung down vertically and I could just push up on it. Once they were broken loose I used the Gear Wrench ratcheting box wrench to finish it off. Let me tell you something about those ratcheting box wrenches...worth their weight in gold ($50 at NAPA). They were slim, strong and made a huge difference in the time it takes to get the bolts off. Anyway, the fronts were easy to get off. I used a tall jack stand to support them while working. I just applied a large "C" clamp to the piston and they were ready to go back on. I did not disconnect the brake lines or remove the underbody protection. I found there was plenty of room to work on them where they were.

The rear brakes are what killed me. Youch. I did the right rear brake first. I had to remove the rear bolts on the underbody protection and loosen the front bolts so that it would hang down a fraction of an inch. The part of the underbody protection that mounts to the brackets stuck up a fraction of an inch above the brackets and I need that room in order to swing the rear calipers over the brackets. It was a tight fit, but once it's resting on the brackets it's easy to work on them. Then came the tough part. The piston is 2.5" in diameter and has to be turned (clockwise as you look at the top of the piston) in addition to being compressed. Plus, the emergency brake attaches to the back of the caliper so getting a "C" clamp on it is impossible. Turns out the channel-locks I had weren't big enough to get around the caliper. Picked one up at Pep-Boys for $27. With that I was able to easily turn the caliper and then use a breaker bar to pry the piston back into the caliper. This is very time consuming and tiring because you have to maintain a strong grip on the piston/pliers and you can only turn it a few degrees at a time due to the tight space. I was finally able to get the caliper compressed enough to fit the new brakes on. Talk about a sense of accomplishment. Of course I still had to do the left rear caliper.

Left rear caliper...I got it half way in and it started freezing up on me. This one took me about 3.5 hours to do. The space is even tighter and I could turn the caliper in even smaller increments. I did finally manage to get the caliper compressed and the brakes pads installed, but it was not easy.

Let me give anyone thinking of doing this a small bit of advice...BUY THE TOOL!!! I can't guarantee that the brake compression tool for the rear brakes will work great, but I can tell you first hand that the channel-lock/pry-bar method does NOT work great. There was definitely room in there to get the tool onto the caliper while still connected to the brake line, and it would have made the job a LOT easier. I tried getting a wheel puller in there to compress the caliper but because the wheel puller is large and round it wouldn't seat properly. Sometimes there is no substitute for the right tool. I'm going to buy one myself first thing on Monday.

I have to say that even though it took my 9 hours to do these, it was worth the $800+ I saved by doing it myself vs. the dealer price. Next time I think I can do all four in less than three hours (maybe as little as two) with the right tool for the rear calipers.

BTW - based on the photos of the caliper cut-up, I figured that the optimal amount to turn the piston before compressing is approximately 1/3 turn. 1/4 to be safe. It worked for me.



If you do not plan on buying the brake tool, you can always disconnect the rear calipers from the brake lines and drop them down out of the truck. This is how I do mine, it is easier that way, I use a normal caliper compression tool, compress the caliper then turn it with channel locks as I compress the caliper. This method works the best, I hate worring about twisting the break line off as I compress the calipers. There is one hitch, dot 5 silicon fluid is expensive. However if you know how to bleed brakes it is breeze.


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