Wednesday, January 18, 2017 Detailed Auto Topics
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Many folks believe that a long-lasting, trouble free set of tires ends with selecting a quality brand. Actually selecting a quality tire is only the beginning. Shockingly, a new high quality tire can be quickly ruined by improper installation.

Replacing the tire on a wheel is known as mounting. It may also be a source of many problems. While it seems quite straight forward, things can go wrong. An untrained person can quickly destroy a new tire by improper mounting. Just a few of the problems that can occur include:

  • Bending or distorting the bead


  • Not fully seating the bead to the wheel


  • Damaging cords in the tire


  • Tearing the bead

Bending or distorting a tire bead 

Wire is wrapped into a bundle, around the openings of a tire. This is the backbone of the tire and is known as the tire bead. When mounting the tire to the wheel, the bead must pass over the wheel. The outer edge of a wheel is larger in diameter than the bead of the tire. This helps keep the tire on the wheel. For instance, in this illustration, "a" represents the diameter of the wheel and "b" the size of the tire opening. Mounting the tire involves a bit of knowledge and care.

Wheel and tire diameters

Wheels are built with a smaller diameter "drop" in the center. Dimension "c" is smaller than dimension "b" allowing a tire to be mounted.

Mounting diameter of a wheel

Great care must be taken to keep the tire in the dropped area while mounting. The width of the tire tends to push the bead out of the dropped area, toward the mounting surface of the wheel. When this happens the tire will be stretched over the wheel. Using force in an attempt to do so can bend and distort the steel belts and the tire's bead. A tire can be twisted out of round and even permanently distorted by such an error.

A tire bead not fully seated to the wheel

A tire must slide over a well lubricated wheel to mount properlyOnce the tire beads are in the dropped center of the wheel, actual final mounting begins.  The tire bead must "travel" from the dropped opening to the edge of the wheel. This happens as the tire is filled with air. Air expands the sidewalls and forces the tire to seat at the edge of the wheel.

There is a slight bump the tire must pass over, at the edge of the wheel.  This bump helps keep the inflated tire in place.  The lower edge of the tire and the mounting surface of the wheel are also built at matching angles.  Properly mounted, this produces an air-tight seal and is also an area of great concern.

 

Rubber is a naturally high-friction material. The tire will resist sliding on a dry or improperly lubricated wheel. Special lubricant must be carefully applied to the tire and the wheel surface to allow proper mounting. If only the tire is lubricated, as often occurs, the lubricant will be rubbed off as the tire moves across the wheel surface. When this happens the tire binds. The result could be an improperly seated tire and possibly a distorted tire carcass.

The bead area and the wheel surface must be lubriated when mounting a tire 

Damaging tire cords while mounting the tire

An unlubricated tire will not seat properly and adding more air pressure to the tire is NOT the answer. The loud pop as the tire slams against the edge of the wheel may be the sound of a new tire being destroyed. Tires are designed to hold no more than the specified amount of pressure. Over inflating, to compensate for improperly mounting, can cause permanent damage to a new tire.

Tearing a tire bead

Lack of lubrication or skill can also cause a tear in the bead of the tire.  A torn bead may not seat to the wheel.  This can result in loss of air, tire failure and a torn bead is non-repairable.  With so many things that can go wrong, great care should be taken in selecting a shop for tires.  Buying a quality tire may not be enough.  Even great tires can quickly be ruined by improper mounting.  Choose a shop known for quality in everything they do.  For quality Michelin tires, mounted properly choose AGCO, its the place to go.





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