How to properly store high-performance tires | Articles

Given our wide-ranging testing program, we inventory a lot of tires, so it takes a long time to burn through any particular set. How do we keep them minty fresh for optimal performance over the long haul–especially as today’s front-running Super 200 tires typically gain performance as the tread wears away?

Before we answer that, let’s talk theory. The rubber compounds in a tire are cooked during manufacturing in a process known as vulcanization, which turns a short-lasting gooey rubber gum into something that holds shape and resists abrasive wear. The process was discovered by Charles Goodyear way back in 1839 when he accidently dropped some raw rubber mixed with sulfur onto a hot stove, causing it to become rigid but still flexible. U.S. patent 1090 describes the process that begat the entire tire industry.

Dubbed vulcanization by Goodyear, the procedure subjects raw rubber to heat, pressure and various activator and accelerator compounds–most notably sulfur–to form a witch’s brew unique to every tire compound. Upward of 100 different ingredients can be present in the formulations of a tread cap compound, which is how manufacturers dial in the inevitable trade-offs between grip, durability and heat tolerance.

Photograph courtesy Wikipedia

Much like baking a cake, every ingredient matters–as does the duration and intensity of the heat and pressure. Unfortunately, the vulcanization process does not completely end when the tire pops out of the mold. Instead, the rubber continues to harden over time. Think of it as a slow-burning fuse, gradually altering the performance characteristics of the tire.

Despite nearly a century of progress–see the black-and-white photo above–vulcanizing rubber is still about heating it up and letting it cure. Photograph courtesy Vitour

This is why freshness of tires matters. The born-on date required of every DOT-marked tire shows the week in which it was made. General industry convention is that tires 6 to 8 years old have aged out regardless of mileage/use and should be replaced.

Photograph by Andy Hollis

The tires used in motorsports rarely last that long simply due to tread life, however. The grippier they are, the more quickly they abrade–yet the more fun they produce.

The real enemy of motorsports tires is heat cycling. Long-term vulcanization is accelerated in spurts through cycles of heat generated during use. Imagine a perfectly cooked steak that you keep putting back in the oven for a few minutes once every hour. Soon enough, it’s way past well done.

So it is with rubber. Every heating and cooling cycle accelerates the burn of that slow fuse, altering the performance characteristics of the tire. How deep and long each cycle is determines how much fuse is burned.

Run a tire for an 8-hour endurance race, and you’ve sucked a lot of the life out of the tire, regardless of remaining tread depth. Conversely, a three-lap time trial session is much easier on a tire. That said, anecdotal evidence supports the notion that frequency of cycles are more important than depth. Cooling down is where the negative effects are produced.

One way to mitigate this process in non-endurance use is to keep the tires on a low simmer using electric tire blankets between sessions during the day. A beneficial side effect is that there’s no need for a warmup lap before putting down a flyer.

Proper storage between uses is also key to longevity. If the tires are subjected to regular street use, they’ll continue to burn their fuse through mild but frequent cycling. Storing them in a shed out in the yard isn’t much better, as temperatures will continue to fluctuate.

The gold standard–and what we do–is to store them off the car in a well-ventilated, climate-controlled shop. That way, continued vulcanization is minimized to a slow burn rate. Further, the tires being loose as they cool minimizes any cold-set flat spots that can develop when a warm tire cools down with load on it. Some tires–notably the Hoosier TrackAttack Pro–exhibit this trait and will take a few miles of use before they loosen up and become fully round again.

Photograph by Andy Hollis

Climate-controlled storage also removes the risk of cold weather damage. Rubber compounds have a chemical characteristic known as the glass transition point. The sticky rubber seen in racing slicks, R-comps and 200tw street tires will change to a more solid state in near-freezing temperatures. Any use in that condition will crack the rubber, destroying the tire.

Manufacturers place warnings on these summer-only tires to inform consumers of the inherent danger. Such tires subjected to freezing temps can sometimes be thawed out and used again, but continued freeze/thaw cycles will hurt performance long-term.

Photograph courtesy Tire Rack

In addition to its heating effects, the sun’s UV rays will also harm a tire by prematurely breaking down the rubber. This is why you see tire covers on vehicles and trailers stored outside for long periods of time.

Another detrimental hazard to tires is ozone, which can be produced by electric motors and furnaces, so your basement or machine shop might not be a good storage choice. The solvents and chemicals you spray in your shop can also attack rubber. If you can smell it, it can affect your tires.

Airtight bagging of your tires can also help slow atmospheric evaporation of oils in the rubber compound. Airing them down to relieve internal pressure will also help keep the oils from being pushed out of a mounted tire.

Photograph by Andy Hollis

Keep in mind that every tire model is different and will respond in different ways to negative effects. But these tips should help you get the most usable life out of each set of tires you mount up.

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