We are often weary of supposed bolt-ons, so the idea of a bolt-on brake kit scared us.
It's very common that off-the-shelf parts require the machining of something or changing additional parts to work correctly, and the brake system is not where you want to mess up. But after living with 35-inch tires on our '08 Jeep Wrangler Unlimited for about a year, we gave in to the temptation of an easy brake upgrade and decided to give the TeraFlex JK Big Brake Kit a try.
Bigger is better, but do you know why? There are three key reasons why larger brakes are better. The first is swept area, or the total surface area that the brake pads contact the rotor. Just like a larger tire patch on the ground means better traction, more pad on the rotor equals better braking power. The stock brakes provide 234.3 square inches of swept area; the bigger TeraFlex brakes provide 272.8 square inches. That's an increase of about 16 percent. Next is how far away the clamping action happens from the axle centerline. It's the same physics that make bolts easier to loosen with a 2-foot breaker bar compared to a 6-inch ratchet. The farther from the axle centerline that the pads ride on the rotors, the greater the stopping power. So larger diameter rotors equal more potential stopping force. Finally, the caliper can make a big difference. Essentially, a bigger caliper with larger pistons can squeeze harder, as long as the master cylinder can provide sufficient pressure and volume.
In addition to giving you improvements in all of these categories, this brake kit also includes performance pads. These have a friction material that is more aggressive, providing more grip on the rotor. The downside is that they can wear the rotors a bit quicker than stock, but TeraFlex feels that the material used gives you a happy medium between ultimate performance and longevity.
How's It Work
There is no proportioning valve to change on the '07-present Wrangler because brake pressure is managed through the factory computer. The ABS, ESP, brake traction control, and hill start assist are also unaffected by this upgrade. These systems will perform just like stock with the bigger brakes in place.
Once we bolted the bigger brakes onto our JK we did some before-and-after testing, as well as a seat-of-the-pants evaluation. We noticed two things right away. The first one isn't a positive-the brake pedal doesn't feel quite as firm as it did with the factory brakes. This is because it takes a lot more fluid to work the larger front calipers. The feeling isn't unacceptable, and the second thing we noticed makes it worthwhile-the initial braking action is much improved over stock. This is a bolt-on improvement that you can feel every time you apply the brakes.
To finish off our evaluation, we went to a secret Michigan testing facility and clicked off multiple before-and-after 60-0 mph tests. We applied full pressure to the pedal and let the ABS work to provide maximum pressure at the brakes. In stock form, the heavy Jeep stopped in an average of 125 feet. With the TeraFlex JK Big Brake Kit, our average fell to 108 feet, for almost a 15-percent improvement. That's a car length, which can be the critical distance you need to stay off the 6 o'clock news and return confidence in your braking power.
The TeraFlex Big Brake kit...
The TeraFlex Big Brake kit for JKs is pretty straightforward. It includes dual-piston calipers, 13.3-inch diameter slotted rotors (stock front rotors measure 11.9 inches) and more aggressive brake pads. TeraFlex feels that this is about the biggest brake upgrade possible without causing undesirable side effects or needing to change the master cylinder.
Be careful to not pull on...
Be careful to not pull on the ABS sensor wire (arrow) as you unbolt the caliper. It's best to unclip it from the brake line before you move the caliper. To minimize the mess don't remove the brake line yet, but also be careful not to damage the line or let the caliper hang from it. If your Jeep frontend has never been apart, you'll have push-on clips over some of the wheel studs holding the rotor in place. We had road grime and salt holding our rotors onto the unitbearings and had them break it free with a plastic mallet.
The floating section of the...
The floating section of the caliper hinges upward when you remove the lower pin bolt, making brake pad swaps quick and easy. The pads have clips at the ends that sit in grooves (A and B) machined into the caliper. There is also an adhesive back on the pads (C), all of which are designed to minimize unwanted brake noise like squeaking. The pads are the same as '09 Ram 1500 parts to make finding replacements easy. The new calipers have dual 56mm pistons, while the factory had a single 66mm pis
It's a good idea to use a...
It's a good idea to use a wire brush to clean up the unitbearing where the new rotor will sit. The rotor slides on using the smaller of the two bolt circles. They fit stock JK 5-on-5 and aftermarket 5-on-5.5 lug patterns. The new caliper installs using the original bolts, which should be torqued to 120 lb-ft. Make sure you mount the calipers with the bleed screw on the top. There is a left and right caliper to make sure that this is possible.
The last step is the biggest...
The last step is the biggest pain. Connect the original brake lines to the new calipers using the new copper banjo washers provided. Refill the master cylinder with DOT 3 fluid and start bleeding the brakes. We had to go around to each caliper three times before we got the pedal feel close to stock. Buy a big bottle of brake fluid. Those huge front calipers are thirsty the first time you fill them.
Bed Your Brakes
Actually...
Bed Your Brakes
Actually the term is bed-in. It refers to a procedure that lets you get the most from new brakes, and it's mandatory with performance brakes. This transfers a layer of material from the pads to the rotors through gradual increases in heat. It gives the pads the best grip on the rotors and minimizes brake noise and vibration. To bed-in a new set of brakes, do ten moderately hard decelerations (without activating the ABS) from 30-10 mph with about 30 seconds between each stop. Don't come to a complete stop until you're done with all 10. Then let the vehicle sit for 15 minutes. Next, perform five moderate decelerations from 60-15 mph with 30-second breaks. Let the brakes cool for 30 minutes and you're done.