Project E36 M3 - Squealing Brakes September 03 2013
I had been running Axxis Ultimate brake pads and ran into some problems with some massive brake squealing. From 30 to 0 mph, the brakes would squeal like a teenage girl at a Bieber concert. I tried cleaning the brakes with brake cleaner, but that only stopped the squealing for about 30 miles before the squealing came back. Willing to try almost anything at this point, I saw a bottle of Disc Brake Quiet at the local automotive supply store and decided to give it a try.
The gooey substance is applied to the back of the brake pads, and after it dries, it absorbs the high frequency vibrations that generate the squealing noise.The first step is to get the car in the air and take the wheel off. Doing brake work on BMW's is pretty easy. Pop off the retaining clip on the outboard side of the caliper and remove the two bolts that hold the caliper on, and the caliper is free. Remove the brake pad wear sensor, and hang the caliper on something so that the brake line doesn't support the entire weight of the caliper. The brake line was never intended to support that much weight. I used a rope to hang the caliper off of the spring, but you can use stiff wire, bungee cords or even a belt.
With the caliper off, the brake pads come right out. I applied several beads of Disc Brake Quiet to the backs of the pads and then spread it evenly with a razor blade. The directions say to apply it liberally, so I put a thick layer on. Be mindful of getting this on yourself if you are in the State of California. This product is known to the State of California to cause cancer and reproductive harm. Luckily we were working in the State of Texas, where cancer and reproductive harm is not applicable.
The directions also say that it dries quickly enough to be installed in 10 minutes and the pads can be installed while the product is still tacky. I found this to be bovine feces. About an hour later, it had dried enough to be borderline acceptable to install. If I were to do it again, I would budget several hours for the product to dry properly.
You may have noticed all the greasy smudges that I had left on the rotor from handling it. This is obviously not good for the function of the brakes and I cleaned them off with some brake parts cleaner. Be careful not to inhale the fumes or get any of this stuff on your skin. The product says it is not for use in California, which means it is pretty serious stuff.
The pads were re-installed, and the caliper put back on. Note that the product will be visible on the outboard surface of the brake pad. If your brakes show the brake pads, you could end up with an undesirable look. Our E36 M3's brake calipers are already painted red, so this worked out fine for us.
So did the product end up eliminating the squeal? We drove for several hundred miles and the squealing was mostly gone. It would still squeal ever so slightly on occasions, but it was virtually gone, and I would consider the project to be a success. We went from frantic-dying-baby-seal levels of squealing to Yugo-drag-launch levels of squealing.
Pros: Works mostly as advertised. Inexpensive. Simple to apply.
Cons: Takes longer to dry than claimed. Conspicuous color may be undesirable. Still allows for some squealing. Causes cancer and reproductive harm if used in California.
Verdict: If you have squealing brakes even after cleaning your brakes with brake cleaner, this is worth a try, but don't expect perfection.