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The Tire Doctor Responds:
The way a tire is mounted can affect both tire wear and ride disturbance.
Extra care in the shop can prevent problems down the road. |
What does “concentric” mean?
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 right). 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. |
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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, fill
out the business reply card bound into this issue of Real Answers. 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. |
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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 proper 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 initial 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. |
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