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ZJ and WJ Brake Upgrade

stillenzjbrakeupgrade.jpg (18011 bytes)By James Hasler

Most ZJ and WJ Grand Cherokee owners that I know love their trucks but hate their brakes. The two piece, composite rotors are prone to warping and don't stop a 4,000 lb. vehicle all that well. After 30,000 miles on my 97 ZJ, my rotors were so badly warped that the whole vehicle would shake violently when braking at speeds over 40 mph. It's a bit disconcerting to my passengers...

After hearing about all sorts of brake related problems on the Jeeps Unlimited Grand Cherokee Forum, I didn't want to spend a dime on turning my stock rotors. I was looking for a true brake upgrade that would not only help my ZJ stop better, but also be a lot more resilient to warping. So, I talked to my friend, Nick, who knows his stuff and he recommended Stillen's cross-drilled Sport Rotors, Performance Friction Carbon Metallic front pads and Stillen Metal Matrix rear pads. In Nick's experience, this was the best setup and would be exactly what I was looking for. I have never worked on disc brakes before, so Nick also supplied me with detailed instructions along with the parts.

So, what's so great about the Stillen Sport Rotors? For starters, they are of a one piece design which is much more resilient to warping compared with the stock 2 piece design. The rotors are also cross-drilled and utilize a unique radius-chamfer designed to help dissipate heat. They also look pretty cool, too!

The pads are also an upgrade since they are metallic and offer a higher friction coefficient compared with the stock pads. However, they are no harder than the rotors so they should last at least as long as the factory parts. There's also a benefit in that metallic pads do not produce as much brake dust as conventional pads...this is a plus for those of you who like to keep your trucks sparkling...

So, with instructions in hand, I spent the next 3 hours installing the rotors and pads.

The first step is to prepare the new rotors. Clean them off with brake cleaner in order to remove any particles left over from the machining process. Nick recommended painting the inside and outside of the rotor's "hat" with a high temp. enamel to resist rust. I didn't have time as my old brakes were downright dangerous, but I'm going to do this step in the near future.

Next, I put the front of my ZJ up on jack stands and placed the two tires under the frame (just in case...) On the back side of the caliper, you'll see the two caliper bolts which need to be removed. Once removed, pull the top part of the caliper towards the rear of the vehicle. Once the caliper has cleared the upper slide rail, you can lift the caliper slightly upwards and remove it from the rotor.

Most people recommend using a coat hanger or zip tie to hang the caliper from the coil spring while you're removing the rotor. This works great, but my brake line was long enough to allow me to set the caliper on the tire that I had placed under the front, lower control arm.

I then pulled the two retainer clips holding the rotor onto the lug nuts. The rotor then pulls right off. It may require a light tap with a hammer if you've got some rust on your hub. You can then pop on the new Stillen rotor. Remember that the rotors are side specific, so use the correct one.

Wow! With rotors like these, it makes me want to get some thin spoked wheels and cruise the town looking for Explorer's to race!!

After the rotor is on, put the retainer clips back on...if they are in one piece...mine ended up in the grass somewhere as I was pulling them off.

Next, remove the old pads from the caliper. This requires removing the outer pad first. I simply used a screw driver and bent the retainer clips until the pad was able to be lifted off. The inner pad simply snaps off. Just pull it off the caliper piston.

The new pads are going to be thicker than the old ones, so in order to get the pads over the rotors, you'll need to push the caliper piston in as far as it will go. This requires a c-clamp.

This will, however, drive brake fluid back up into the reservoir. Some people recommend opening the reservoir cover and siphon fluid off if it gets to high. Others open the bleeder valve as they are pushing the piston towards the bottom of its bore in order to get rid of the excess fluid. I chose the first option but since the reservoir is somewhat transparent, I chose to simply monitor the level without opening it up.

Once the piston has been pushed all of the way in, you can put on the new pads. Once again make sure you examine the pads and put the correct ones on as they are side specific. First snap on the pad that fits onto the caliper piston. Then, put the outer pad on. Make sure it is completely seated.

Here's the caliper with the new pads installed.

You should examine the caliper bolt boots to make sure that they are not torn and lubricate them with high temperature grease. You should also grease the upper and lower slider rails and liberally grease the caliper bolts. Now you can replace the caliper by first fitting the caliper onto the lower slide rail and then pushing it until it contacts the upper rail. You might need to hold the caliper boots out of the way during this. All that's left is to torque the caliper bolts to 7-15 ft-lbs. Here's the completed front setup.

The rear is just as easy as long as you remember to release the parking brake...otherwise you'll spend an eternity sloshing Liquid Wrench onto the lug nuts and beating on the rotor. Your neighbors will probably come and beat on you if this happens.

The lower rear caliper bolt will most likely not be able to be removed all of the way until you begin to slide the caliper off of the rotor. This is because the bolt hits the shock absorber. The caliper is removed by pulling the bottom of the caliper off first, rather than pulling the top as done on the front brakes. You'll definitely need a bored (boring?) friend or a zip tie to hang the caliper from this time, as the brake line is way too short to do much of anything.

The brake pads and rotors are removed exactly as they are on the front. Once again, make sure to put the correct rotor and pads on the correct side of the vehicle. You'll also have to use the c-clamp trick here as well. Here's what the completed rear brakes look like. It's pretty cool how the inside of the rear rotor "hat" is actually the parking brake's drum...

Finally, here's s shot of the rotor being seen through the wheel. Now those Explorer's are going to be REALLY scared!!!

When you first start-up the truck, you'll notice that the brake pedal will go to the floor. Pumping the brakes a bit will get the pedal feel back to normal as you move the new pads into position.

Stillen has some recommended break-in procedures that you should follow, although they seem to be a bit on the paranoid side.

So far, although I haven't put that many miles on the new setup, the new brakes seem to stop MUCH better. I have forgotten what it's like to stop and not do the "60 mile-an-hour jiggle". I have gotten an occasional light squeak out of them from time to time and they do seem to make a noise right before the truck comes to a deep stop. I'm guessing this is the small price to pay for using metallic pads. Overall, I'm very pleased with the Stillen rotors and I think they are a great upgrade for any ZJ owner.

 

Thanks James for sharing this great write up with us at NAGCA!

   

 

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