Correct mounting and demounting of motorcycle/ bicycle/ rickshaw/ wheel-barrow tyres and tubes are essential for maximum safety and economy. It is a specialized job that should be done only by fully trained persons with the proper tools and with careful attention to specific instructions and established procedures.
Motorcycle/ bicycle/ rickshaw/ wheel-barrow tyres are designed to be operated up to or at rated inflation pressure. Exceeding these pressures may cause the motorcycle/ bicycle/ rickshaw/ wheel-barrow wheel or tyre to explode, which can result in serious or fatal injury.
Pressure Regulators should always be used to help prevent injury or death caused by over-pressurization of the tyre assembly. Maintenance and use of pressure regulators should be performed in accordance with the manufacturer’s instructions. The safety practices for mounting and demounting motorcycle/ bicycle/ rickshaw/ wheel-barrow tyres referenced in the motorcycle/ bicycle/ rickshaw/ wheel-barrow and wheel manufacturer’s instructions should be followed.
NEWLY ASSEMBLED TYRES AND WHEELS SHOULD BE INFLATED IN SAFETY CAGES.
Motorcycle/ Bicycle/ Rickshaw/ Wheel-barrow Wheels
Motorcycle/ bicycle/ rickshaw/ wheel-barrow wheels made today, for tube-type, are the split wheel or demountable spoke-supported variety. While this makes the job of mounting and demounting physically easier, strict attention to detail is required.
Wheel Manufacturer’s Instructions
Specific instructions on modern wheels are educated to OEMs and after-sales handlers by the motorcycle/ bicycle/ rickshaw/ wheel-barrow manufacturer or directly from the wheel manufacturer. You should not mount or demount motorcycle/ bicycle/ rickshaw/ wheel-barrow tyres without the specific information supplied. In addition, refer to motorcycle/ bicycle/ rickshaw/ wheel-barrow manufacturer’s instructions on use of incline ramps and/or jacks for maintenance purposes.
Safety Precautions with Wheels
An inflated tyre/wheel assembly is potentially explosive. Mounting and demounting of motorcycle/ bicycle/ rickshaw/ wheel-barrow tyres is a specialized job that is best done with the correct equipment and properly trained personnel and with careful attention to specific instructions and established procedures.
Bead lubrication in mounting both tubeless and tube-type tyres is often desirable to facilitate mounting and seating of the beads against the wheel flanges. A light coat of talc can be used. Use the following guidelines for mounting:
• Use a direct reading or dial type pressure gauge with 5 psi increments that is calibrated on a regular basis.
• When inflating a tyre/wheel assembly, regulate the supply line to a pressure no more than 50% higher than the tyre service pressure.
• Do not inflate a tyre above rated pressure to seat beads.
FAILURE TO COMPLY WITH THE FOLLOWING INSTRUCTIONS MAY CAUSE TYRE/TUBE/WHEEL FAILURE AND SERIOUS OR FATAL INJURY.
• For inspection use only enough pressure to round out tube. Excessive inflation strains splices and may cause fabric separation of reinforced tubes. Do not inflate tube larger than tyre.
• Ensure that any manufacturing stickers on the tyre innerliner are removed to prevent damage to the tube.
• Use the correct tyre and tube for the wheel assembly.
• Inspect the tube, looking for cuts or cracks.
• Inspect the inside of the tyre, and remove stickers or any sharp edges.
• Clean the bead base with a cloth dampened with denatured alcohol. Allow bead seat area to dry.
• Clean inside of tyre, then lubricate lightly with talc.
• Inflate tube to slightly round, and insert in tyre.
• Align valve on tube with red balance dot on tyre.
• When mounting tyre and tube on wheel, be sure that wheel bolts are torqued to wheel manufacturer’s instructions before inflating.
• Inflate tyre in a safety cage to rated pressure.
• Deflate assembly to equalize stretch.
• Re-inflate to rated pressure.
• After 12 hour stretch period, re-inflate to rated inflation pressure.
Within the next 24 hours, if the pressure decreases more than 5%, pressure loss could be caused by trapped air between the tyre and tube, valve core leakage, or a damaged tube. The assembly should not be placed into service.
Check inflation pressure daily or before first flight when tyres are cool.
Inflation Pressure Loss in Tube Type Assemblies
There are three reasons for inflation pressure loss in a tube-type tyre:
1. A hole in the tube
2. A damaged valve stem
3. A nonfunctional valve core
Finding an inflation leak is usually simple. The first step is to check the valve and tighten or replace the core if it is defective. If the valve is not leaking, demount the tyre, remove the tube, and locate the leak (by immersion in water if necessary). Replace the tube.
Inflation Pressure Loss in Tubeless Assemblies
Since there are many causes for inflation pressure loss with a tubeless assembly, a systematic troubleshooting approach is advisable. Moreover, when chronic but not excessive inflation pressure loss exists, other factors such as inaccurate gauges, air temperature fluctuations, changes in maintenance personnel, etc., may be the source. If a definite physical fault is indicated, a troubleshooting procedure similar to the one outlined below is recommended.
If pressure drops more than five percent (5%) in the 24 hours:
1. Check with water or soap solution:
• valve core
• valve seal
• pressure release plug
• wheel base and flanges
2. If no leaks are found, rerun 24 hour diffusion check. If pressure still drops more than 5%, disassemble tyre/wheel assembly.
• Check wheel for cracks, porosity, fuse plug or pressure release plug malfunction.
Before deflating and removing tyre, check the valve. Put a drop of water or soap solution on the end of the valve and watch for bubbles indicating escaping pressure. Tighten valve core if loose. Replace valve core if nonfunctional and repeat leak test to check. Check the valve stem and its mounting for leaks with a soap solution. If a leak is detected, deflate the tyre/wheel assembly and replace the valve core and/or valve assembly. Make certain that every valve has a cap to retain inflation and prevent dirt, oil, and moisture from damaging the core.
Gas escaping through a cracked or porous wheel base is usually visible in an immersion test. Consult the wheel manufacturer’s manual for rim maintenance and repair.
Beads and Flanges
Check the bead and flange areas of a tyre for leaks before demounting. This can be done either by immersion or by using a soap solution. Any of the following factors can cause air loss:
• Dirty or corroded wheel bead seating surfaces.
• Damaged or improperly seated tyre bead.
Before demounting, use an immersion test or soap spray to determine if the tyre itself has a puncture. If a puncture is found in the tread or sidewall, the tyre must be scrapped.
Pressure Retention Test
When no leaks can be found on the prior checks, a pressure retention test must be performed. The tyre should be inflated to operating pressure for at least 12 hours before starting the test. This allows sufficient time for the casing to stretch, but can result in apparent inflation pressure loss. The tyre must be re-inflated after the stretch period to operating pressure. Allow the tyre to stand at constant temperature for a 24-hour period and recheck pressure.
Special Procedures – Emergency Tyre Stretch
In an emergency situation, tyres which must be placed in service without being inflated a minimum of 12 hours should be inflated to 105% of the unloaded service pressure. The tyre/wheel/valve assembly should be sprayed with a soap solution and checked for abnormal leakage (abnormal leakage occurs when the soap solution bubbles between the tyre and wheel or if a constant stream of bubbles is produced at the tyre vents). If there is abnormal leakage, the tyre/wheel assembly should be rebuilt according to normal procedures. If there is no abnormal leakage, the tyre can be placed in service, as long as cold tyre pressure is checked before every flight within the next 48 hours and the tyre is re-inflated if necessary.