So you just spent all this time and money to replace your brakes, and they’re already squealing every time you pull up to a stoplight — or worse, maybe you’re feeling that annoying brake shudder already. So are your brakes defective? They should last for years before this happens, right?
I can almost guarantee your brakes are not defective. What we have here in both of the scenarios outlined above is probably a case of not bedding in your pads properly, and a few other possible factors. Plus we’ll go through some things that manufacturers like EBC are doing to help alleviate these issues moving forward.
What does it mean to bed-in your brakes, and why does it need to be done?
Bedding in your brakes is the process to “mate” your pads to the surface of the brake rotor with gradually increased heat cycles in order to create a thin, even film of pad material on the surface of the rotor. But why does this need to be done? To answer that, we need to get into how modern disc brakes work. I’ll also include a guide at the bottom of the article on how it’s done.
Your brakes take advantage of two forms of friction to do their job – abrasive and adherent friction:
Abrasive friction: When the brake pads are pressed against the spinning rotors, the two materials scrape by each other, breaking down the crystalline structure of the pad and even the smooth cast iron surface of the disc. This process turns the kinetic energy of the spinning rotor into heat, slowing you down in the process.
Adherent friction: The brake pad material breaks apart and reforms, bonding to the surface of the rotor. This process saps kinetic energy from the spinning rotor, spending that energy to create that bond, and expend the rest of that energy as heat. This form of friction is critical to brake bedding procedures.
All modern brake pads use both types of friction, though to varying degrees depending on the pad material and application. Semi-metallic pads for instance work primarily through abrasive friction, and because of this they tend to be a little tougher on rotors and create more dust. The trade off here is in better high temperature performance, and is a material you will most often see used in high performance and towing applications. Meanwhile organic and ceramic pads take better advantage of adherent friction, making them easier on rotors, allowing for generally better cold performance, and tend to be quieter at the expense of high temperature effectiveness.
OK, so with that out of the way, how does this apply to shuddering brakes?
If your rotors haven’t been properly bedded, then you can end up with an uneven distribution of pad material deposits on the surface of the disc. In the beginning, this just makes for uneven levels of grip across the surface, causing the pads to grip, then slip, then grip, and so on, leaving you with that juddering feeling that you can feel vibrating the car, or even through to the steering wheel. If this goes on for too long, this can and will result in uneven rotor wear and temperature spread — ultimately resulting in what most would describe as a “warped” rotor. Rotors don’t generally warp, this is a bit of a misnomer, they wear unevenly mostly due to improper bedding or the bedding was removed from overly aggressive use.
Alright, what about new brakes squeaking?
This one is particularly annoying, because not only are you annoying the people around you, but squeaking brakes usually means they need to be replaced. Did they wear out that quickly? Nope! This confusion comes from the fact that most brake pads have a built in metal tab that ride on the rotor once the pads wear down to a certain level.
However if new pads are making this noise, it’s actually your rotor that is “singing.” What’s happening here is that the conditions are just right for the disc to vibrate as it passes between the clamping pads, through a mechanism that is actually pretty similar to a bow being dragged across the strings of a violin. The difference here being that violins make a sound that we actually want to hear, while the sound coming from your brakes isn’t exactly what I would call a symphony.
Proper bedding of your pads to the rotors can solve the issue in some cases, but there are a few other things that can contribute to the issue. For one, dirt or a small layer of rust on the surface of the hub that you’re placing the rotor against can cause the rotor to sit on a slightly uneven surface, giving the disc some play to vibrate as it turns. Another possibility would be a tiny amount of play in your brake pads. This can be solved with brake shims or some sort of lubricant between the pad and the caliper. Auto parts stores will try to sell you this stuff for a premium, but a little bit of anti-seize will work just as well.
So before you go through the hassle of trying to return or exchange your now used parts, try some of the things in this guide and save yourself a headache — especially when you could just end up right back where you started with the new stuff.
How to bed-in your brakes:
I definitely recommend going by the pad manufacturer’s specific instructions on how they want you to do this, but here is my general recommendation on the procedure (for most pads):
- Find an open and preferably empty stretch of road that will allow you to repeatedly go through this procedure (the process might look a little odd to onlookers)
- Accelerate to 35 mph and apply moderate brake pressure to reduce your speed to 5-10 MPH
- Repeat this process 3-4 times to get some heat into the brake pads
- Now turn up the heat even more by increasing your speed to 45 mph and braking down to 10 mph
- Repeat this process 3-4 times
- Coast as much as possible for 5-10 minutes
- Now park the car and allow the brakes to fully cool for an hour.
EBC pads, however, come with a surface coating to help bed-in your pads, and that changes the procedure quite a bit. Instead of doing those very specific cycles like laid out above, you just… drive. Well, mostly.
For street applications, EBC recommends:
- Gentle braking for the first 100 miles (obviously except for emergency stops)
- Flowing from 60 mph to 10 mph 5 times in a row
- Drive slowly for a few minutes to let your brakes cool
For track or race use, EBC recommends 200-300 miles of urban driving, or if that’s not possible:
- Drive a lap, steadily applying the brakes every few seconds
- Coasting for a lap without any unnecessary braking
- Drive a third lap while applying the brakes slightly harder each time
- Drive a final cool down lap
- Don’t park with the brakes hot
Pro-tip: It’s important to avoid coming to a complete stop during final bed-in stages, as it’s possible to melt your pads against the hot rotors and imprint pad material in one spot on the rotor. Of course it goes without saying to still use common sense and stay safe, so brake if a deer or pedestrian jumps out into the road, or more importantly if you spot Sasquatch and need to grab a picture.
So if you new brakes are making noise, don’t worry! It’s fixable! Have any other ideas that I might have missed? Drop a comment below!