Cleaning Extreme Brake Dust Off Wheels September 29 2022

Our BMW E46 M3 had brake dust caked onto some of the corners of our wheels from the previous owner. I had tried for years to get it out. Every time I would wash the car, I would focus on those spots and scrub them with a toothbrush, hoping that enough scrubbing over time would eventually loosen the brake dust, but it didn't. I tried dedicated wheel cleaners. I looked up what others on the internet had done. I tried Goo Gone, but it didn't work. I tried to clay bar the spots, to no avail. I tried carefully picking at it with a razor blade to no effect. I even tried masking the surrounding area and trying a small stainless steel brush, and that didn't do anything. These were progressively aggressive methods, but I felt that I was probably going to have to refinish these wheels and had nothing to lose by trying.

BMW BBS wheel with extreme brake dust that is difficult to remove.

I was about to replace my tires, and was thinking it would be a convenient time to refinish the wheels. Before committing to a $1000 wheel refinishing, I did one last search on the internet to see if there were any aggressive cleaning methods left to try. I came across a lot of comments on forums saying that Sonax Wheel Cleaner worked for them and I thought it was worth a shot. This is a product that I don't recall being on the market at the time when I had first started this journey.

Stack of wheels with a bottle of Sonax wheel cleaner in the foreground.

The directions say to spray it over your wheels, let it sit for 3-5 minutes and then rinse it off. Using it per the directions got all of the recent brake dust off, but not the caked-on brake dust that I had been fighting for years. A second application got a little more off, and I could tell it was working because it changes from yellow to purple as it works. Rinsing with a pressure washer did help a little, but it was no magic bullet. The directions say that agitating with a brush can help, so I proceeded to apply and then scrub the stains with a nylon bristle brush. After a couple of hours, this technique got most of the stubborn spots off the rear wheels after a few applications, but the scrubbing technique could still not clean the front wheels with severe brake dust. Nonetheless, I kept trying because the Wheel Cleaner kept changing color, and it seemed like it was still doing something with each application. However, after many hours of scrubbing and reapplying, progress had slowed, and I decided to change tactics.The new idea would be to soak the stains in the Wheel Cleaner and let the chemicals do the work.

Small puddles of Sonax wheel cleaner forming between the wheel spokes.

However, there are two problems with this method. The first is that the wheel cleaner won't stay on any surface that isn't horizontal, and the second is that the product will dry up before you get a good soak. 

I developed a method where saturated strips of toilet paper are placed on top of the stains to keep the Wheel Cleaner in contact with the stains, and then the toilet paper is covered with plastic cling wrap to keep it from drying out.

Toilet paper soaked in Sonax and covered with plastic cling wrap.

4 layers of Charmin seemed like it held enough wheel cleaner to keep the area wet for a good soak. I would leave this setup to marinate for up to 24 hours, and then remove the toilet paper and plastic wrap.

Some scrubbing with a nylon bristle brush would get some of the now-softened brake dust off. I rinsed the wheels after each marinating session. Some areas had to have multiple marinating sessions, but eventually, I was able to get them all.

Before and after shows less brake dust remains after treating.

The photo above shows the progress after each soaking session.

Interior of the wheel barrel being treated with toilet paper soaked in Sonax wheel cleaner and plastic cling wrap covering it.

I also did the same thing on the barrels of the wheels. The majority of the stains on the barrels only required one soaking session.

There are some limits to how well the saturated toilet paper can stick on vertical or up-side down surfaces. I recommend only using this technique on the bottom third of the wheel at a time. Because of this, it takes a lot of rotating, waiting and repeating. It took me about an entire week to get all the stains out, so plan accordingly, depending on the severity of your brake dust stains. I ended up going through one and a half 500 ml bottles of Wheel Cleaner.

Note that this soaking technique is not what Sonax recommends. I'm not a chemist, nor do I fully understand what the chemicals in the product are doing to the brake dust or wheel finish. Sonax instructs to not let the product dry on the wheel, but I don't know if that simply makes rinsing more difficult, or whether it poses a danger to your wheel finish if it is left on too long. I personally did not notice any deleterious effects on my wheels with the factory finish, but your experience may differ. Sonax asserts that their wheel cleaner is non-acidic and pH neutral.

I was ecstatic with finally finding a product that could take off my baked-on brake dust. I ended up saving $1000 by not having to have my wheels refinished, and my wheels look dramatically nicer now. If you have extreme brake dust stains you haven't been able to get out, Sonax Wheel Cleaner combined with this soaking technique might be able to dissolve those stubborn stains.

Here's a link to the exact product I used: Sonax Wheel Cleaner

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