Rockcrawling and wheel damage...
Rockcrawling and wheel damage go hand in hand. Professional rockcrawlers know this. That's why so many competition rigs have protective bead locks like the ones shown here. With this arrangement, very little damage can result from direct wheel-to-rock impact. A super-thick outer bead-lock ring protects the recessed bolt heads and prevents anything from reaching the face of the wheel.
Cause: Improper bolts.
This bead-lock wheel was the type where an off-the-shelf wheel is modified to accept a bead lock. While many enthusiasts run this type of wheel, we don't recommend it. Our reasoning lies in the long list of variables that the end user must deal with to ensure safe operation.
Effect: Injury.
As you can see, this wheel broke apart. The story goes like this: Our good friend (and Editor of 4-Wheel Drive & Sport Utility) Phillip Howell was assembling the outer "lock" ring to the bead receiver ring. As Howell sandwiched the tire bead between the two rings, he inadvertently failed to notice that each of the Grade-8 bolts was too long for the arrangement. Subsequently, as each bolt was tightened, the ones near the spokes bottomed out, acting like little jack screws. When Howell finished torquing the bolts, he made another mistake by filling the tire with a short hand-style air chuck instead of a longer safety lead. Together, with 30 psi inside the tire and the stress caused by the jack screws, the welds securing the bead-lock receiver ring to the wheel simply couldn't handle the pressure and failed. The results left Howell hospitalized with a cracked kneecap, broken fingers, and both hands swollen to the size of softballs.
The most common cause of tire failure is improper inflation pressure. Different wheels require different types of valve stems. Using the improper valve stem can result in slow leaks which, when unchecked, compromise safety and wheel function. The one shown here is the metal type that requires a rubber grommet to be sandwiched between a flange and a hex nut. Over the course of time, the hex nuts can loosen up and/or the grommet can flatten, causing slow leaks. Everybody knows it's important to check air pressure periodically, but many fail to realize the importance of replacing valve stems every time you replace your tires.
This picture shows the traditional type of rubber valve stems found on most wheels. Notice that one is larger than the other one. The two sizes are not interchangeable. One common issue we've seen with this type of valve stem relates to the internal valve core. Sometimes people forget to secure the cap after adding air or airing down. In this scenario, we've seen the valve core actually unthread itself and cause a flat tire while the vehicle is in motion. This can be avoided by simply replacing the cap after servicing the tire. Locking caps are also available to alleviate this problem.
Some of you may have stumbled into one of these little guys on a newer light pickup or SUV. What they are is a pressure-sensitive transmitter developed as part of the federal Transportation Recall Enhancement, Accountability and Documentations Act (TREAD). It was passed back in 2000 in response to a major recall of defective tires. These little sensors alert drivers when tire pressure drops below 25 percent of the manufacturer's recommended inflation pressure. The system is mandatory for all new vehicles with GVW ratings under 10,000 pounds, sold in the United States, beginning with the 2006 model year. On the upside, these little buggers are saving lives; as a drawback, they are rather delicate and feature temperamental seals that can easily be damaged during regular tire servicing. Unfortunately, they aren't cheap to replace, either, so if your rig has them, use caution whenever working around them.
Someday we may see a total shift in the way tires and wheels are manufactured. This photo shows the Tweel by Michelin. Essentially, it's an airless, integrated tire-and-wheel combination designed to take the pneumatic variable out of the equation. Instead of air pressure, the Tweel uses a series of energy-absorbing polyurethane spokes to dampen surface imperfections. It's believed that the first applications for this new technology will likely be used by military, where flat-proof tires would be a huge advantage to troops. At this time, we can only assume that the Tweel will eventually trickle down to everything from trail rigs to toy haulers. However, exactly when is unknown.