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Technical Bulletins

Mounting Tires on Deep Drop Center Rims

Mounting of tires on deep drop center rims requires additional care during the mounting and inflation process.

When the tire is mounted on the rim in a vertical position, the tire beads may drop into the rim drop center on the top side and hang beyond the rim flange contour on the bottom side, as illustrated in Figure 1.

To assure proper mounting, tire lubricant should be applied to both tire beads, the rim taper and flange area. The rim should then be positioned so it is concentric with the tire beads as the assembly is inflated, as shown in Figure 2.

In addition, tire demounting and mounting safety precautions should be followed, as in the attached warnings. If there are any questions, call Firestone Sales Engineering at 1-800-847-3364.


Tire changing can be dangerous, and should be done by trained personnel using proper tools and procedures. Before servicing tires, always read and understand any manufacturer's warning contained in the customer's literature or molded into the tire sidewall.

Failure to comply with these procedures may result in faulty positioning of the tire and/or rim parts, and cause the assembly to burst with explosive force, sufficient to cause serious physical injury or death. Never mount or use damaged tires or rims.

For detailed tire demounting and mounting procedures, refer to RMA "Demounting and Mounting Procedures For Agricultural Tires" poster available from:

Rubber Manufacturing Association
1400 K Street NW
Washington, D.C. 20005



NOTE: Under some circumstances, the trajectory may deviate from its expected path.

Always use a safety cage or other restraining device in compliance with OSHA regulations.


Reinflation of any type of tire/rim assembly that has been operated in a run-flat or underinflated condition (80% or less of recommended pressure), can result in serious injury or death. The tire may be damaged on the inside and can explode while you are adding air. The rim parts may be worn, damaged or dislodged and can explosively separate.

Never rework, weld, heat, or braze the tire/wheel/rim. Heating the rim of tire/wheel/rim assembly can cause a tire to explode, causing serious injury or death.

The use of any flammable material during tire servicing is absolutely prohibited. Use of starting fluid, ether, gasoline or any other flammable material to lubricate, seal or seat the beads of a tubeless tire can cause the tire to explode or can cause the explosive separation of the tire/rim assembly resulting in serious injury or death.

Never hammer, strike or pry on any type of tire/rim assembly while the tire contains inflation pressure. Do not attempt to seat any part while the tire contains any inflation pressure. This could result in serious injury or death.


Never inflate beyond 35 pounds pressure to seat beds.
Never stand, lean or reach over the assembly during inflation.

Inspect both sides of the tire to be sure that the beads are evenly seated. If tire is mounted on a machine that does not have a positive lockdown device to hold the wheel, inflation should be done in a safety cage or other restraining device. If both beads are not properly seated when pressure reaches 35 psi, completely deflate the assembly, reposition the tire and/or tube on the rim, relubricate and reinflate. Inflating beyond 35 psi air pressure when trying to seat the beads is a DANGEROUS PRACTICE that may break a tire bead (or even the rim) with explosive force, possibly resulting in serious injury or death. After the beads are fully seated, pressure may be increased above 35 psi to operating pressures, not to exceed the maximum molded on the tire sidewall.


Never reinflate a tire that has been operated in a run-flat or underinflated condition (80% or less of recommended pressure). Demount and inspect all tires and rim parts before reinflating.
Always use specialized tools as recommended by tire suppliers for mounting and demounting of tires.
Before loosening any nuts or clamps that attach a multi-piece rim assembly to a vehicle, always completely deflate the tire (both tires of a dual assembly) by taking out the valve core(s). Never attempt to demount a tire from a rim unless you are sure that the tire is completely deflated. Failure to follow this practice can cause the assembly to burst with force sufficient to cause serious injury or death.
Never use any rim part that is bent, pitted from corrosion, cracked or worn. These are unserviceable parts and must be destroyed so that they cannot be used. Remove rust, dirt or foreign material from rim parts.
Never use a rim part unless you can positively identify it from the manufacturer's stamped markings. If you cannot identify a part, it must be destroyed.
Always inspect inside of tire for loose cords, cuts, penetrating objects or other casing damage. Repairable damage must be repaired before placing tire back into service. Tires with unrepairable damage should be destroyed.
Never substitute an innertube for a permissible or non-permissible repair.
Always replace a tire with one having the same rim diameter designation and suffix letters.
Always inspect inside of the tire and remove dirt, liquids, or other foreign material before mounting.
Never install tubes that have buckled or been creased.
Always use new tubes in new tires.
Always use radial tubes with radial tires.
Never use a tube in a casing larger or smaller than that for which the tube was designed by the manufacturer.
Always check to be sure tube is clean before installing in tire.
Always lubricate with only approved tire mounting lubricant or mild vegetable oil soap solution. Never use antifreeze, silicones or petroleum-base lubricants. This will damage the tire.
Always inspect valve cores for proper air retention. Replace damaged or leaky cores.
Always inflate tire to tire manufacturer's recommended cold inflation pressure for the tire's intended service.
When inflating a tire off a vehicle, use a safety cage or other restraining device, and an extension hose with in-line air gauge and clip-on air chuck, which allows the operator to stand clear of the trajectory.
For tube-type tires, inflate to service pressure without the valve core installed and the completely deflate the tire to prevent wrinkles in the tube. Insert the valve core and reinflate the tires to recommended service pressure as specified for the tire and/or rim.
Always use sealing valve caps to prevent loss of air or fluid.