A Crash Course in Brake Squeal
A while back, CA ran a tech article on brake basics. It covered the basics of changing the rotors and pads out while going over the importance of brakes in big builds. At the time we used EBC pads with Stoptech rotors. The pads were the ceramic Red Stuff series from EBC, a street compound, designed for better stopping performance and low dust output. The pads were installed without inserts, and used high temp brake grease instead. After the break in period, (No pun intended, no really…) we were pleased to find that these Red Stuff pads were in fact what they advertised. The bite was crisp and clean and the performance of the pads was more than noticeable. As hard as we tried we could not get the pads to fade, and bite was consistent throughout the entire experiment. However there was one problem, the noise. It was by no means bad, just a slight squeal every once in a while, but it bothered the crap out of us. We originally thought the pads were to blame, but upon further investigation, we found that the EBC ceramic pads we loved so much were not the cause of the dreaded squeal. Some of you may be quick to point out that we failed to insert the silencers that would help with this problem, annnnnd you would be right. Sort of. But before we can get into that can of worms, we should probably go over the reason for squealing, as the cause may surprise you. The squealing noise you are hearing is caused by vibration between the pad and rotor or caliper. Squealing, for most of us, seems to only occur at certain speeds. This is due to the fact that vibration frequency is in the range of hearing at that particular speed, hence higher speeds fail to make any sound. So although the squealing sound is only heard at say 20mph, the vibrations are present at all speeds. The key to stopping squeal lies within removing vibration between the pad and contact surfaces. This is accomplished by moving the vibration frequency out of audible range. Now that we know the causes the noise we can work on killing it. There are two schools of thought in regards to handling the noise. The first revolves around separating the pads from the calipers. This can be done with grease or inserts, or both, however the problem often returns. Grease works well for a certain period of time, but after a while the heat generated from braking melts even the best greases away. If you use grease it’s important to note the following. Don’t put grease on the side of the pad that contacts the rotor, duh. Use the grease to coat the back of the pad (caliper side) as well as the mount points for the pad. This creates a barrier between the two surfaces that absorbs the vibration. The other method focuses on inserts. Simply put, a more permanent form of the grease such as foam pads that cushion the pad and caliper, reducing noise. These pads work well, and typically don’t melt, however they still allow for some squeal due to their solid nature. Inserts are pretty straight forward, just place them between the caliper and pad and you are finished. Be warned however, that this is no guarantee for removing unwanted squeal. The second school of thought relies on increasing mass to reduce noise. It maintains that by gluing the pads to the calipers, the pads mass is increased and thus the vibration frequency is moved out of audible range. This can be done by using an adhesive that uses no access to oxygen for bonding. The reason for this being that the constant compression of the brakes will force out any air between the pad and caliper over time. This method works very well, and gets rid of almost all audible squealing. There is a down side however, because this method requires gluing the pads to the calipers, replacing the pads can be very difficult. The glue method with add time to replacement jobs. It’s also important to note that no glue can go on the pot or piston. Failure to keep the pots clear could result in damage to the calipers. So there you have it, a quick look at how to kill the squeal. Whatever your path, make sure you do it well, craft is everything here. Happy wrenching.
Cover Photo courtesy of ECS Tuning