Chances are you've encountered tire blooming and you don't even know it. Blooming is what causes a tire to look brown. That new set of tires that you have to scrub over and over again to get them to look black, or the tires on a car you detail less frequently that are closer to the color of chocolate than they are black. Modern rubber compounds are becoming increasingly complex, far more than most people realize. Tire manufactures are continually pushing the envelop with chemistry and design to create tires that can keep up with the demand of todays cars and drivers. Higher mileage, more miles per gallon, better all-weather traction, or high speed and cornering as cars get better, faster, more intense the tires they roll on must change to keep up.
We expect increased performance from our vehicles and tires are an integral part of that, but rarely do we take the time to understand what exactly has changed about tires other than going from bias ply to radial in the late 1960's.
What does this all have to do with your tires turning brown? Read on.
An anti-ozonant is probably something you've never heard of. Its an organic compound added to rubber materials that prevents, or at the very least, slows the deterioration caused by exposure to the elements. Anti-ozonants are used as an additive in most all of the exterior rubber and plastic parts to one degree or another, but they are most prevalent in tire manufacturing. The anti-ozonant additive keeps plastics and rubbers from becoming dry, brittle, oxidized or cracking. It does this by preventing the surface of the material from oxidizing and keeps the material pliable.
Thanks to anti-ozonants in rubber compounds we have have high mileage tires, performance tires, and everything in between. Without it sports cars would shred tires incredibly fast after just a few high speed turns or long track runs where the tires were heated up. Even your daily driven commuter car would need tires far more often as the sun and heat slowly rotted away the rubber compounds.
Tire rubber compounds are designed in a way that allows the anti-ozonant to continually work its way to the outside of the tire and as such, continually keeps the outer surface and sidewall pliable and resistant to oxidation.
Once anti-ozonant reaches the outside of the tire and is exposed to air and moisture it oxidizes, the result being a brownish residue. The term for this ugly brownish tire look is 'tire blooming'. Just like metals left exposed to the outside world will slowly begin to rust (oxidize) as it is exposed to water and air, so does the anti-ozonant component of the tire rubber.
Making matters worse is the use of mold releases in the manufacturing processes. These lubricant type chemicals provide a non-stick surface for the inside of a tire mold. The mold release chemical bonds with the tire and hold anti-ozonants onto the surface of the tire.
While some people will point to mold release as the primary and/or only source of tire blooming, it is in fact often times only a part of the problem. Even after the removal of mold release a tire will continue to push anti-ozonant to the surface allowing the brown residue to return.
THE ROLE OF COLOR CHANGING WHEEL CLEANERS
Wheel cleaners used to dissolve metallic contamination (Wheel Cleaner among them) can have an accelerating effect on the oxidation of anti-ozonant. The reaction you see when brake dust it turned to a reddish slurry by Deep Wheel Cleaner or a similar product is, in a very simplified way, oxidation. The chemical reacts with the metallic contamination and begins to dissolve it.
Tires that have not been cleaned properly before or have been left uncleaned for long periods of time will have substantial amounts of the anti-ozonant built up on the surface of the tire. When an active wheel cleaner comes into contact with this buildup it will accelerate the browning or blooming. Because of this its imperative to regularly scrub tires to remove the buildup of anti-ozonant and 'dead' rubber - think of it almost like exfoliating your skin. If you are a regular user of Deep Wheel Cleaner or similar color changing wheel cleaners for their ability to remove stubborn brake dust then be sure to spend an extra couple of minutes scrubbing your tires as well.
Does this necessarily mean you should discontinue the use of Deep Wheel Cleaner? No, but it should be used with the understanding that the tire needs deep cleaning after the wheel to remove any residues or prevent tire blooming acceleration as a result of the oxidation process. Abrading the tire sidewall to remove this will prevent the blooming in the first place - the reason your sidewalls brown, but your treads don't is that the treads are continually worn away by driving so the surface never is allowed to sit long enough to display blooming.
DON'T BLAME THE SILICONE
For years the prevailing thought has been that silicone based tire dressings are the culprit for brown tires. Read any number of forums and the first thing most casual detailers will point to is the choice of tire shine the person with the issue uses. While silicone can be a messy and sticky solution to making your tires shine it isn't always the main culprit of the brown issue.
Most browning related to silicone will be due to the silicone holding dirt and debris on the tires surface, not the tire itself turning brown. This type of browning is very easy to remove as silicone dressings also remove with scrubbing and a degreaser like All Purpose Cleaner.
Don't think this means you should immediately start to treat your tires with tons of silicone, there are still a lot of reasons it's not an ideal way to dress your tires, but don't believe the story that your choice of tire dressing is the ONLY source for the brown residue. Silicone and water based dressings can be used and the tire can still exhibit blooming... its the tires surfaces and/or lack of heavy cleaning more than it is anything you've treated it with.
REMOVING THE BLOOMING
Removing the blooming is really a simple process - the use of a good degreasing agent, like Adam's All Purpose Cleaner, and a stiff bristle brush should be more than enough to remove even the worst blooming within a few treatments. Be sure to rinse the tires extremely well with clean after each cleaning to remove any chemical buildup.
Once the brown residues are removed regular cleanings with All Purpose Cleaner shouldn't need to be as aggressive or frequent, but if you notice the blooming returning just scrub well. The application of a quality water based dressing like Super VRT or a dressing low in silicone content like Adam's Tire Shine will help slow the reappearance of blooming by providing a barrier between the tire surface and the environment.
IT WILL COME BACK, ITS JUST A QUESTION OF WHEN
Because anti-ozonants continue to work their way towards the outside of the tire even a car which sees very little use or doesn't have very dirty tires may experience tire blooming when eventually exposed to oxidizers due to lack of cleaning. As such it is recommended that even relatively clean tires be treated to a semi-regular scrubbing to remove the anti-ozonants from the outer layer of the tire sidewalls.
Each tire will have a different amount of blooming it is prone to. Some tires may bloom very slowly, while others will bloom almost before your very eyes. The amount of anti-ozonant and the way the tire is designed to push it to the surface will determine how fast or slow it happens. Regardless, one thing remains true - regular cleaning and dressing of your tires will prevent or at the very least minimize the appearance of brown on your tires.