No matter if you’re working on a light truck, high-performance vehicle or commercial truck, centering is the foundation of each wheel balance that is performed on the vehicle. It’s a foundational process that allows the technician to get the best ride quality and achieve customer satisfaction.
However, there’s more that goes into the process than many think; if centering isn’t done properly, a technician’s balance and eccentricity measurements won’t be reliable. If the wheel isn’t centered on the balancer, and then centered on the vehicle at the same center line, the technician’s measurements are thrown off, resulting in a customer comeback down the line with a tire vibration complaint.
To avoid those comebacks and save time at your shop, I’ve outlined a few best practices and tips to help you and your techs make sure you get the correct balance each time.
Centering Best Practices
- When the wheels are removed from the hub, clean the back side of the wheel, the hub bore, the mounting hub of the vehicle around the studs and the hub face of the rotor. In today’s market, there’s a wide variety of tools, such as a power drill brush, that can be helpful when performing this task.
- Select the proper tooling or adapters so that the wheel is mounted as close to the same center line to be perfectly centered and protect the wheel from damage.
- In most cases, the best way to center a wheel is with a centering cone from the backside of the wheel through the hub bore, avoiding contact with the inside of the wheel or other parts such as the trim cap hole. When a technician takes a cone and puts it in the wheel, he/she has to make sure that it doesn’t strike out inside the wheel before centering it. One way to validate that this is being done correctly is to place the cone in the back side of the wheel, twist it and look at the imprint that it puts on the centering cone face. In general, the lower the taper of the cone, the better centering you’ll achieve since the cone has less potential of striking out inside the wheel and not contacting the hub bore.
- To clamp the front of the wheel during the centering process, use flange plates or pin plates with a centering cone to protect the wheel. When a technician uses a flange plate, it encourages him/her to do back-cone mounting, offering the best centering and wheel protection at the same time. Common clad chrome wheels, which have a plastic face and trim cap hole, require back-cone mounting with a flange plate to prevent cracks in the cladding and damage to the wheel by incorrectly centering from the front side. With an alloy wheel that’s painted or clad, push the pin plate against a lug nut hole tapers, not the face of the wheel. Wheels with larger and heavier hub bores, common on larger light trucks, commercial trucks and heavy-duty trucks, may require front-cone mounting because the hub boards are too large for back-cone mounting. Companies such as Haweka, or other wheel balancer tooling companies, sell centering tools for larger light trucks and commercial vehicles that aid in centering heavy wheels with large hub bores using back-side centering and flange plates. It’s the best way to center “bar none.”
- To double-check that the wheel is centered once it is clamped on a balancer, a technician can do a simple check: write down the balance readings as well as the amount and location of the wheel weights. Then, loosen the wheel, reposition it on the tooling and write down those measurements again. They should be the same or the wheel should repeat within the smallest increment of wheel weight used. For example, if a technician is using quarter-ounce wheel weights, the measurement should repeat within a quarter ounce. The mass of the wheel and the increment of the wheel weight size dictate the level of centering that’s necessary because you can’t balance any smaller than the smallest increment of the correction weight. This test also checks the repeatability of the balancer to make sure that it is performing properly and that there are no issues such as worn shafts or bent hubs.
- The correct eccentricity measurement, taken by a capable balancer, is crucial to the centering process. Since eccentricity is permanent, you have eccentricity in the tire and wheel assembly at all times — not only when the rim is bent, and the tire is out of round. If a customer comes in complaining of a vibration issue, first road test the vehicle and warm up the tires before taking an eccentricity measurement since the tire can take a temporary flat spot when sitting. When mounting a tire, also pay attention to how it is seated on the rim. It’s important to seal and seep the bead, then deflate the tire, bring it up to placard pressure and install the valve core. This helps ensure that tire is seated properly on the rim to reduce eccentricity.
- If you have a balancer that can take eccentricity measurements, you can perform an eccentricity reduction process, otherwise known as hub matching. Do this by taking the high point of the tire and wheel and marking it on the balancer before you remove it. Then, place the tire and wheel assembly on the vehicle with that high point at the top center to maintain clearance between the hub and the hub bore. As you let go of the wheel and start tightening the lug nuts, the wheel will drop slightly, and the gap will end up at the bottom. This process allows you to do the best possible job balancing the wheel with centering.
Dave Scribner is a product development manager with deep roots in automotive wheel service equipment, including several patents in iconic wheel balancing equipment. He has held various product development roles at Hunter Engineering, Bosch, Snap-On Equipment and CEMB USA. Contact Dave at [email protected].
Check out the rest of the July digital edition of Tire Review here.