Story and Photography by Ryan Lee Price
So, you’ve got a set of four new tires and you want them wrapped around the wheels that are already on your car. It’s a common situation, but the trouble is your old bald tires; they’re still on the vehicle, right? If you happen to own tire irons, a big hammer and some sizeable biceps, you might be able to break the tire bead seals, but you could damage the wheels quite easily. Plus, the odds are good that you don’t have a tire balancing machine… they’re expensive and take up a lot of room. Instead of going DIY, in this case, it is much more fun to watch it being done. Let’s take an inside look at how professionals replace tires.
The first step, of course, is removing the wheels from the car. At a shop, they jack the whole car off the ground to make it easier to balance the tires on the car itself (more on this later). Most of the action takes place around two machines. The first piece of equipment the tire visits is the tire changer, which costs a couple grand. After the air is let out of the tire (by removing the valve stem completely), the tire is lined up with the side-mounted bead loosener, which uses a pneumatic arm to pinch the tire enough to break its seal on the wheel. The shovel-sized head on this mechanism replaces you hitting the tire with a hammer.
Once the bead is broken on both sides and the tire is flopping around the rim, it is hoisted up on the table top of the tire changer, and a pickup truck or SUV wheel/tire combination weighs nearly 100 lbs., so it can be rather cumbersome to wield around. There are four rubber-tipped clamping arms that grab and secure the wheel without scratching it, while the operator slips between the wheel and tire separation head that has a polymer insert to further protect the wheel. With a flick of the foot petal, the wheel begins to turn, while the stationary separation head pulls the tire from the inside of the rim to the outside. Sometimes, the tire needs a little coaxing with the tire irons.
The process is repeated for the inside bead as well, pulling the tire completely off of the rim from the top. A brand new inflation valve is inserted and the new tire is prepped for its place on the rim by bathing the bead with soapy water. This helps the tire slip over the rim easier. With the help of a couple of tire irons, the tire changer's separation head becomes a joining head, pushing the tire's beads over the rim. With a tire this size, it can be a tough job.
The pin in the new valve stem is temporarily removed so 50 lbs. of air can be pumped into the tire quickly. Then it is off to the balancing machine. The process is simple in a shop but virtually impossible to do at home without special equipment. Balanced tires not only ride smoother and safer but last longer and offer an even wear throughout the tire's life. The tire and wheel are clamped onto the spoke via the wheel's lug pattern and the machine verifies electronically that the wheel is perfectly centered.
Once the balancer is started, it only takes about 10 seconds for the machine to measure the tire's balance and not only suggest the amount of weight needed to fix the imperfection in the tire but it also shows exactly where the weights need to be added. Each square of weight equals one-quarter ounce and is glued to the inside of the wheel, out of sight.
Now the new tire/wheel combination is ready to be fitted back on the car, where it will be tightened to the correct specification. Normally, we encourage you to tackle projects yourself with the help of our extensive database at http://www.chiltondiy.com. However, some things — like replacing tires — are best left to the professionals with the big, expensive machines.
Not only is Ryan Lee Price a freelance writer specializing in automotive journalism and a former long-time magazine editor, he is part of the technical editorial team that provides content for most all of the ChiltonPRO and ChiltonDIY products. He currently resides in Corona, California, with his wife Kara and their two children.