From a Great post on SurfCityGarageForums...(and Dylan of course) "My tires are have a brown residue on them, what can I do to fix them?" Modern rubber compounds are pretty interesting and very complex, far more than most people realize. The stresses today's cars put on rubber are far higher than ever before. Higher speeds, more torque, higher heat, longer miles, stronger lateral forces, more driving. We expect tires to put up with all of it as our cars get faster and more powerful, 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. ANTI-OZONANT An anti-ozonant, is an organic compound added to materials that prevents or slows the deterioration caused by exposure to the elements. As we all have experienced with plastic or rubber trim on our cars it oxidizes over time and can become faded, chalky, or even brittle and cracked. 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. Without the addition to anti-ozonants to modern tires it would be highly unlikely we'd have high mileage tires. Performance 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 driver, or commuter car would need tires far more often as the sun and heat slowly rotted away the rubber compounds. The addition of anti-ozonants to modern tires has allowed tire performance to keep up with the demands of ever increasing levels of power or strain placed thru them as a result of improved vehicle performance. TIRE BLOOMING Todays rubber is designed intentionally in a manner that allows the anti-ozonant constantly to work its way to the outside of the tire and as such, continually keeps the outer surface and sidewall pliable and resistant to oxidation. After the anti-ozonant works its way to the outside of the tire and is exposed to air it oxidizes, and begins to turn brown. The term for this ugly brownish tire look is blooming. As you know, oxidation is a chemical reaction. An unplated nail left exposed to the outside world will slowly begin to rust (oxidize) as it is exposed to water and air. Anti-ozonant has a similar problem. Exposure to air and water will cause the exposed anti-ozonant to oxidize and leave a rusty brownish residue behind. The longer a tire goes between thorough cleanings the more likely it is to begin to display blooming. Compounding the issue is the use of mold releases in modern tire manufacturing processes. These lubricant type chemicals provide a non-stick surface for the inside of a tire production mold. The problem becomes their ability to bond with the tire and hold anti-ozonants onto the surface of the tire. Some detailing experts will point to mold release as the primary and only source of tire blooming, which is incorrect. Even after the removal of mold release a tire will begin to leach anti-ozonant to the surface allowing the brown residue to return. WHEEL CLEANERS AND THEIR ROLE Cleaning compounds used to dissolve metallic contamination (like Active Wheel Cleaner Plus) can have an accelerating effect on the anti-ozonant as they are essentially an oxidizer. The reaction you see when brake dust it turned to a reddish slurry by Active Wheel Cleaner Plus or a similar product is, in a very simplified way, oxidation. The chemical reacts with the metallic particle and begins to dissolve it. Tires that have not been cleaned properly or have been neglected for long periods of time will have substantial amounts of the anti-ozonant on the surface. When an oxidizing wheel cleaner comes into contact with this buildup it will accelerate the browning or blooming. To this end it becomes imperative to regularly scrub tires to remove the buildup of anti-ozonant and 'dead' rubber compound, especially if you are a fan of Active Wheel Cleaner Plus or similar cleaners for their ability to remove stubborn brake dust from wheels. Does this necessarily mean you should discontinue the use of active wheel cleaners? No, but they should be used with the understanding that the tire needs deep cleaning either before or after the wheel to remove any residues or prevent tire blooming acceleration as a result of the oxidation process. THE SILICONE SCAPEGOAT There are those in the detailing business that would have you believe that silicone based tire dressings are the culprit for brown tires. While silicone can be a messy and sticky solution to making your tires shine it isn't always the main culprit. Most browning as a result from silicone will be due to the tendency of silicone to be wet and greasy, thus holding dirt and debris on the tires surface. This type of contamination is generally easy to remove as silicone dressings also remove with scrubbing and a degreaser. This doesn't necessarily mean that you should immediately start to treat your tires with silicone, there are still many reasons its a less than ideal way to dress your tires, but don't let any less qualified individuals lead you to believe that your choice of tire dressing is the ONLY source for the brown residue. REMOVING THE BLOOMING To remove the brown residues a strong degreasing agent, such as APC Concentrate, and abrasive scrubbing of the tires surface is recommended. Stiff bristle brushes along with the degreaser will cut thru the oxidized anti-ozonant typically in 1 to 2 treatments. Be sure after each scrubbing that the tire is rinsed well with clean water to remove the cleaning agents as well as the residues that have been freed from the tire. Once the brown residues are removed regular cleanings with a water based degreasing agent and application of water based tire protectant, like Tire Dressing & Conditioner, is recommended to prevent and/or slow the process. Even perfect care cannot always 100% prevent the return of the brown blooming issue in some tire compounds. Because anti-ozonants actively continue to leach 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.