In terms of tire mounting, "concentric" simply means that the center of the wheel or rim is in exactly the same place as the center of the tire mounted on it.

Why is this important?

Depending on how non-concentric the assembly is, drivers may or may not feel ride disturbances. If the mounting is bad enough, ride disturbance will be evident immediately.

More subtle mismounting may not be noticeable at first, but can lead to irregular wear initiation. As irregular wear progresses, it can cause ride disturbance. So, even though non-concentric mounting may not cause vibration immediately, the irregular wear it causes may do so later on.

Doesn't the mounting process automatically make tires and wheels concentric?

Unfortunately, no. Both the tire and wheel must be clean and properly lubricated. Otherwise, the tire bead can get stuck in the wrong position on the rim flange before it is fully and concentrically seated.

What causes tires and wheels to be non-concentric?

Improper mounting procedures, including poor cleaning and inadequate lubrication are the most important factors. If the tire's bead isn't seated properly on the rim flange, the tire and wheel will end up being non-concentric.

In some cases, the assembly acts as if it were out-of-round. The result can be bouncing or thumping - like a tire with a flat spot from brake lock. Left untreated - like a flat spot - this condition can worsen, and may lead to severe irregular wear.

If the tire is crooked on the rim, the result can be like a bent axle or wheel. The tire may wobble and vibrate. That can cause rapid wear, irregular wear, or both.

What do I do if a mount isn't concentric?

Break down the assembly and try again. Check tire and wheel for cleanliness. Relubricate both of them. Align the dots appropriately (see pictures to left). Then, reseat the beads.

If that doesn't get it, try rotating the tire 180 degrees with respect to the wheel, remount and check concentricity again. If you still have no luck, try another tire or another wheel. That may help you pinpoint the problem.

Does a non-concentric mount ever "fix" itself?

Never. But there is some good news: Once a tire is properly mounted, if you maintain proper air pressure, the tire and wheel will stay concentrically mounted.

Is there an easy way to remember all this?

Just remember "Clean, Lube, Align, Check."  Or, memorize the nonsense word "CLAC", made from the first letters of each step. And, if you don't already have a copy of our step-by-step video, Truck Tire Mounting for Customer Satisfaction, Click here to order and we'll send you the video and a free mounting procedure wall chart for your shop.

Please direct any technical questions on concentric mounting, or any other tire-related subject for that matter, to our engineering team at 1-800-847-3272.

What can I do to make sure my tires are concentrically mounted?

We recommend a four step process: Step 1: CLEAN Always clean and inspect wheels and tires carefully. On wheels, bent or dented flanges, rust build-up, dirt or damage can make it impossible for the tire's bead to seat properly. If the bead can't seat properly on the flange, the mount will probably be non-concentric. Bead damage or dirt can cause the same problem, so be sure to check the tire as well.

Step 2: LUBE Be sure to lubricate both the wheel and tire bead. Proper lubrication can reduce bead damage, makes mounting easier, and helps the tire's bead fit easily into the proer place on the rim flange. And remember, avoid both water-based and petroleum-based lubricants. Water-based lubricants can cause both wheels and steel tire cord to rust, while petroleum-based lubricants can destroy rubber over time. We recommend using only a high-quality, vegetable oil-based lubricant for truck tire mounting. Your mounting supplies dealer should be able to provide you with an appropriate lubricant.

Step 3: ALIGN In our last Tire Doctor article, we explained how to use the red and yellow dots you find on Bridgestone tires to help minimize radial runout and aid in intial static balance. Be sure to align any dots correctly. Then, making sure that you follow all OSHA, RMA, tire manufacturer and shop procedures, proceed to seat the beads.

Step 4: CHECK Check the assembly for concentricity. Use the tiny ring that's molded into the tire near the bead, and check its distance from the edge of the bead flange. Check it in at least four locations, 90 degrees apart, and do this on both sides of the tire. The molded ring must be the same distance from the flange in all locations. If you can see a difference, the tire is not concentrically mounted.