Brakes: Pad/Rotor break-in
A few things I wanted to cover here. Not necessarily in this order
1 the proper way to break-in your new pads and rotors.
2 Steps to fix or clean/scrub rotors if there is a vibration
3 There is no such thing as a warped rotor
After talking to a few people in the past its become clear there are some misunderstandings about brakes, rotors and there structure.
Lets knock out this very bad Myth.
Warped Rotors: THERE IS NO SUCH THING AS A WARPED ROTOR
The rotor by design is meant to be rigged and to not bend or twist with TQ applied to it. Tq both in the form of breaking or, in power acceleration from the car. The Rotor due to the structure and resistance to flexing will break before it will warp. The rotor will also crack before it fully breaks.
http://audirevolution.net/addons/albums/images/315042587.jpg
So why do so many people think they have wrapped rotors when they get pulsation under breaking?
Pedal pulsation is caused by several things, and they all tend to have the same common denominator. Its having the brake pads not run on a consistent surface.
When the Rotor has a spot on its surface that grabs more then others your going to feel a pulsation when that spot of the rotor comes into contact with the Pads and with your rotor spinning at certain speeds you can feel that Grab spot more then 30 times a second.
30x a second is a lot. Think about how bad your brakes pulse when your ABS system triggers. the ABS system causes almost the same grab and release pulse that your going to get from a high grab spot on a rotor. Most ABS Systems pulse at 15+ times a second so, to have twice that is going to be much more pronounced.
So what can cause High Grab spots?
A Hot spot on the rotor: This tends to happen after very hard driving and no cool down time.
A hot spot is a section of the rotor, that has brake pad material literally stuck to it or baked in it.
A bad Bedding posses or break-in: This is very common
if both disc and pad are not properly broken in, material transfer between the two materials can take place in a inconstant fashion resulting is uneven deposits this again leads to pulsation under braking.
Unprepared Rotors before install: This too is common and can lead and contribute to bad bedding of the brakes
The rotors have a slick spot on them either from oil or other materials. The brake pads slid on the oil sections and grab on the dry section.
There are other bad brake situations that can cause pulsations, however the above cover most that the general public will see.
/////////////////////////////////////////////: HOW TO BED IN YOUR BRAKE PADS AND ROTORS //////////////////////
I’ve seen this posted several times before and the speeds are posted in KPH. This leads people to think they need to break or bed there pads in at very high speeds.
The Truth is, the speeds needed to bed in your brakes are dependent on your brake pads. Race pads don’t work till there heated up and street pads don’t work well when there too hot. So knowing what pads you have is going to be the first place to start.
For the sake of conversation, lets just assume your using standard OEM pads or there equivalent.
The entire idea behind bedding in the brakes it to get the pads and the surface to have full contact with each other. The idea is to knock down any high spots and get both the faces flat to each other.
bed-in consists of generating enough heat on the pads and the rotors to a brake system to allow the formation of a transfer layer. The idea is to get the brakes up to temperature to start the pad ware then to cool without coming to rest, resulting in an even transfer layer deposition around the rotor circumference. This is repeated three or four times in order to ensure that the entire rotor face is evenly covered with brake pad material and that both the pads and the rotor have been bedded together.
Here is how you do it.
First keep in mind that with brand new pads and rotors your brakes are not going to work the first few times. So find a nice long straightaway. I generally suggest getting the car up to no more then 35mph.
Get the car going 35mph and then lightly start applying brake pressure, you don’t want to abruptly stop the car you actually want to just slow the car down. Apply about 1/2 the brake pressure you would if you were slowing down to a traffic light that is say 500ft away. When you get to about 5mph start the acceleration proses back up to 35mph. Repeat 4 times.
from there I generally let the brakes cool down and I check the fluids again and make sure there are no leaks. After a little while I then would go back out and start doing the same thing but from say 45-60mph
TIP:When doing high speed stops makes sure to avoid keeping your brakes on at a dead stop. If the rotor is super hot and you keep the brakes applied you stand a good chance of baking a large amount of brake pad on the rotor surface where the pads are sitting. This is one of the causes of vibration of pulsing of the brakes.