[h=1]Bedding in Brakes[/h]
Bedding allows your brakes to reach their full potential. Until they are bedded, brakes simply do not work as well as they can. If you've installed a big brake kit, changed pads and rotors, or even purchased a new car, you should set aside time to bed the brakes per the instructions below. Proper bedding improves pedal feel, reduces or eliminates brake squeal, prevents (and often cures) brake judder, reduces brake dust, and extends the life of pads and rotors.

For more details on the theory of bedding, please refer to this article: Pad and Rotor Bed-In Theory, Definitions and Procedures

Caution: Immediately after installing new pads, rotors or a big brake kit, the first few applications of the brakes will result in very little braking power. Gently use the brakes a few times at low speed to build up some grip before blasting down the road at high speed. Otherwise, you may be in for a nasty surprise the first time you hit the brakes at 60 mph.


If you just installed rotors with zinc plating or if the rotors have an anti-corrosion phosphate coating, you should postpone bedding until normal driving has allowed your pads to polish the rotors clean and removed all traces of the plating or coating. If your new brake rotors have an oily anti-corrosion coating, clean this off thoroughly with brake cleaning spray and/or hot soapy water before installation.
Read and understand these instructions completely before starting. If you have questions, give us a call or email. Do not substitute higher speeds for the 60mph called for. The heat in brakes goes up exponentially as you increase the speed from which you brake. Repeated stops from 80 or 90mph with street pads will overheat the brakes and you may end up having to replace pads and rotors.
When following these instructions, avoid other vehicles. Bedding is best done when traffic is light, as other drivers will have no idea what you are up to and may respond in a variety of ways ranging from fear to curiosity to aggression. A police officer will probably not sympathize when you try to explain why you were driving erratically! Zeckhausen Racing does not endorse speeding on public roads and takes no responsibility for injuries or tickets you may receive while following these instructions. Use common sense!

1. From 60mph, gently apply the brakes a couple of times to bring them up to operating temperature. This prevents you from thermally shocking the rotors and pads in the next steps.
   
2. Make eight to ten near-stops from 60mph to about 20 mph. Do it HARD by pressing the brakes firmly, but do not lock the wheels or engage ABS. At the end of each slowdown, immediately accelerate back to 60mph, then apply the brakes again. DO NOT COME TO A COMPLETE STOP! If you stop completely, with your foot on the brake pedal, pad material will be imprinted onto the hot rotors, which could lead to vibration and uneven braking.
   
3. The brakes may begin to fade after the 7th or 8th near-stop. This fade will stabilize, but not completely go away until the brakes have fully cooled. A strong smell from the brakes, and even some smoke, is normal.
   
4. After the last near-stop, accelerate back up to speed and cruise for a few minutes, using the brakes as little as possible to allow them to cool down. Try not to become trapped in traffic or come to a complete stop while the brakes are still hot.
   
5. If full race pads, such as Hawk DTC-70 or Performance Friction PFC11 are being used, add four near-stops from 80 to 20 mph.
   
   
   

After the break-in cycle, there should be a slight blue tint and a light gray film on each rotor face. The blue tint tells you the rotor has reached break-in temperature and the gray film is pad material starting to transfer onto the rotor face. This is what you are looking for. The best braking occurs when there is an even layer of of pad material deposited across the rotors. This minimizes squealing, increases braking torque, and maximizes pad and rotor life.


After the first break in cycle shown above, the brakes may still not be fully broken in. A second bed-in cycle, AFTER the brakes have cooled down fully from the first cycle, may be necessary before the brakes really start to perform well. This is especially true if you have installed new pads on old rotors, since the pads need some usage to conform to the rotor wear pattern. If you've just installed a big brake kit, pedal travel may not feel as firm as you expected. After the second bedding cycle, the pedal will become noticeably firmer. If necessary, bleed the brakes to improve pedal firmness.

 

For more details on the theory of bedding, please refer to this article: Pad and Rotor Bed-In Theory, Definitions and Procedures

 

Bobby Dukes
How many miles on the vehicle? Reason I ask is generally a set of brakes will last a vehicle up to 60K miles before you begin to notice a decline in stopping power. Although mild, this won't really reveal itself until around 80K. That's with no other mechanical issues on stock brakes with just regular driving habits. If you have less than 60K, something else may be wrong (struts often cause a rough vibration when brakes are activated. Might have some wheel pull too).

Vibration on braking "usually" means the pads and/or rotors are worn beyond repair. Micrometer will probably indicate you have about 1 to 2K miles left, in which case it's not worth turning. As an aside, I never...ever...have rotors turned. Drums, yes. Rotors..never. To easy to get a warp for one and two, 80% of a car's stopping power is in the front end. No sense trying to milk out a worn part when my life is at stake. Rear drums I'll turn inside out until I replace them.

Now, I said "usually" because it is entirely possible to lose vaccuum on application of brakes and cause a rough idle. If you were driving a 70s or 80s era, I'd have that looked at first. Generally caused by a blown seal in the brake booster or a ruptured main vaccuum hose...sucks the vaccuum pressure right out of the engine. But since you in a 300 I'm guessing brakes are the issue.

I've recently replaced my stock setup on my 99 GMC Sierra with drilled and slotted rotors and ceramic pads form Powerstop (www.autoanything.com). Good price for a full set up for all four wheels and pads for a trip well over stock. I have no ABS so I went heavy on the new brakes to make up for it. I've heard some snake oil merchants tell me slotted rotors will increase the wear on the pads. meh. Can't say for sure because they all seem to start to wear out around 60K...as I mentioned.

Anyway, my .02 from 13 years of working as a mechanic for the Air Force and plenty of brake jobs on my own cars.