Inspecting Mounted Tyres
Systematic inspection of mounted tyres is strongly recommended for safety and tyre economy. The frequency of the inspection should be determined by the use and normal tyre wear of the particular vehicle involved.
Inspect treads visually and check remaining tread. Tyres should be removed when tread has worn to the base of any groove at any spot, or to a minimum depth as specified in vehicle manuals.
When To Replace
In order to return to a maintenance base,Diamond Tyres Ltd. can remain in service with minutest grove depth just before top ply cord is visible, but only as long as the cord is not worn through or exposed. Tyres within this limit can continue in service no longer than necessary to be replaced.
NOTE: Further use of tyres beyond limits may render a tyre unsafe or fatal.
If tread wear is excessive on one side, the tyre can be demounted and turned around, providing there is no exposed fabric.
DO NOT PROBE CRACKS, CUTS, OR EMBEDDED FOREIGN OBJECTS WHILE TYRE IS INFLATED. THIS COULD CAUSE THE OBJECT TO BECOME A PROJECTILE OR THE TYRE TO EXPLODE, WHICH CAN RESULT IN SERIOUS OR FATAL INJURY.
Remove tyre from service if weather-checking, cracking, cuts and snags extend down to the casing ply in the sidewall and bead areas.
Bulges in any part of tyre tread, sidewall or bead area indicate a separation or damaged tyre. Mark with crayon and remove from service immediately.
Fabric Fraying/Groove Cracking
Tyres should be removed from service if groove cracking exposes fabric or if cracking undercuts tread ribs.
Generally speaking, tyres need not be removed because of flat spots due to sudden impact and braking or hydroplaning skids unless fabric is exposed. If objectionable vibration results, however, rebalance the assembly or remove the tyre from service.
Casing Flat Spotting
Loaded tyres that are left stationary for any length of time can develop temporary flat spots. The degree of this flat spotting depends upon the load, tyre deflection and temperature. Flat spotting is more severe and more difficult to work out during cold weather. Under normal conditions, a flat spot will disappear by the end of the tyre warm up.
Inspect bead areas next to wheel flanges for damage due to excessive heat, especially if brake drag or severe braking has been reported during riding. If damaged, remove tyre from service.
Look for marks on tyres and in wheel wells that might indicate rubbing due to inadequate clearance.
Check wheels for damage. Wheels that are cracked or damaged should be taken out of service for repair or replacement in accordance with manufacturer’s instructions.
Inflation Pressure Loss in Tyre/Wheel Assemblies
Keep the Diamond recommended air pressure for a comfortable ride and proper braking while on road.
Typical Treadwear Patterns
Even treadwear on a tyre indicates that it has been properly maintained and run at correct inflation pressure.
Worn to the breaker/casing plies, the tyre should not be left in service or retreaded.
This is a normal wear pattern on some tyres and can be caused or worsened by under-inflation.
Some vehicle tyres exhibit faster shoulder wear on one shoulder versus the other due to non-tyre influences (unbalanced rim-type wear, etc.). If this condition exists, the tyre’s life can be extended by demounting and reversing (“flipping”) the tyre on the wheel as long as tyre wear limit and the physical condition criteria are satisfied.
Tyres cannot be taken for granted on any motorcycle/ bicycle/ rickshaw/ wheel-barrow. Tyre maintenance costs will be at their lowest and tyre life will be at its longest if proper maintenance practices are observed. Safe tyre operation also depends on proper maintenance. Thus, preventive tyre maintenance leads to safer, more economical operations.
Proper Inflation Procedures
NOTE: Keeping motorcycle/ bicycle/ rickshaw/ wheel-barrow tyres at their correct inflation pressure is the most important factor in any preventive maintenance program. The problems caused by incorrect inflation can be severe. Over-inflation can cause uneven treadwear, reduce traction, make the tread more susceptible to cutting and increase stress on motorcycle/ bicycle/ rickshaw/ wheel-barrow wheels. Under-inflation produces uneven tyre wear and greatly increases stress and flex heating in the tyre, which shortens tyre life and can lead to tyre incidents.
2. Ambient Temperature effects on inflation
3. Increase pressure 4% for tyres under load
4. Allow 12 hour stretch after mounting
5. Never reduce the pressure of hot tyre-remember - 1% pressure change for 5°F (3°C)
6. Equal pressure for front and rear tyres
7. Calibrate inflation gauge regularly
1. Check daily when tyres are cool
Tyre pressures should always be checked with the tyre at ambient temperatures. Tyre temperatures can rise in excess of 200°F (93°C) above ambient during operation. A temperature change of 5°F (3°C) produces approximately one percent (1%) pressure change. It can take up to 3 hours or more after a ride for tyre temperatures to return to ambient.
A tyre/wheel assembly can lose as much as five percent (5%) of the inflation pressure in a 24-hour period and still be considered normal. This means that tyre pressures change on a daily basis. Even a tyre which does not normally lose pressure can become damaged by road factors that can suddenly increase pressure loss. These are all reasons why it is important to check pressure daily or before each ride.
2. Ambient temperature effects on inflation
When tyres are going to be subjected to ambient temperature differences between two locations in excess of 50°F (27°C), inflation pressures should be adjusted to the colder temperature prior to coming onto the road.
3. Increase pressure 4% for tyres under load
It must be determined if “loaded” or “unloaded” pressure has been specified by the motorcycle/ bicycle/ rickshaw/ wheel-barrow manufacturer. When a tyre is under load, the air volume is reduced due to tyre deflection. Therefore, if unloaded pressure has been specified, that number should be increased by four percent (4%) to obtain the equivalent loaded inflation pressure. The opposite is true as well: if loaded pressure has been specified, that number should be reduced by four percent (4%) if the tyre is being inflated while unloaded.
4. Allow 12-hour stretch after mounting
All tyres, particularly bias tyres, will stretch (or grow) after initial mounting. This increased volume of the tyre results in a pressure drop. Consequently, tyres should not be placed in service until they have been inflated a minimum of 12 hours, pressure rechecked, and tyres re-inflated if necessary.
5. Never reduce pressure on a hot tyre
Excess inflation pressure should never be bled off from hot tyres. All adjustments to inflation pressure should be performed on tyres cooled to ambient temperature. Procedures for hot tyre inflation pressure checks are described later in this section.
6. Equal pressure for front and rear tyres
To prevent rear tyre on carrying extra load, both front and rear tyres should be inflated equally. The mate tyre(s) will share the load, allowing individual tyres to run smoothly.
7. Calibrate inflation guage regularly
Use an accurate, calibrated gauge. Inaccurate gauges are a major source of improper inflation pressures. Gauges should be checked periodically and recalibrated as necessary. Diamond recommends the use of a digital or dial gauge with 5 PSI increments and a memory needle.
Mounted Tube-Type Tyres
A tube-type tyre that has been freshly mounted and installed should be closely monitored during the first week of operation, ideally before every ride. Air trapped between the tyre and the tube at the time of mounting will seep out under the beads, through sidewall or around the valve stem, resulting in an underinflated assembly.
Cold pressure settings
The following recommendations apply to cold inflation pressure setting:
1. Minimum service pressure for safe motorcycle/ bicycle/ rickshaw/ wheel-barrow operation is the cold unloaded inflation pressure specified by the manufacturer.
2. The loaded service inflation must be specified four percent (4%) higher than the unloaded inflation.
3. A tolerance of minus zero (-0) to plus five percent (+5%) of the minimum pressure is the recommended operating range.
4. If “in-service” pressure is checked and found to be less than the minimum pressure, the following table should be consulted. An “in-service” tyre is defined as a tyre installed on an operating motorcycle/ bicycle/ rickshaw/ wheel-barrow.
Cold Tyre Service Pressure Recommended Action
100 to 105 percent of loaded service pressure None - normal cold tyre operating range.
95 to less than 100 percent of loaded service pressure Reinflate to specified service pressure.
90 to less than 95 percent of loaded service pressure
Inspect tyre/wheel assembly for cause of pressure loss.
Re-inflate & record in your log book.
Remove tyre/wheel assembly if pressure loss is greater than 5% and reoccurs within 24 hours.
80 to less than 90 percent of loaded service pressure Remove tyre/wheel assembly from motorcycle/ bicycle/ rickshaw/ wheel-barrow.
NOTE: Any tyre removed due to a pressure loss condition should be returned to an authorized repair facility along with a description of the removal reason, to verify that the casing has not sustained internal damage and is acceptable for continued service.
DO NOT APPROACH A TYRE/WHEEL ASSEMBLY THAT SHOWS SIGNS OF PHYSICAL DAMAGE WHICH MIGHT COMPROMISE ITS STRUCTUAL INTEGRITY. THE TYRE COULD EXPLODE, WHICH CAN RESULT IN SERIOUS OR FATAL INJURY. IF SUCH CONDITIONS EXIST, REFER TO OPERATOR SAFETY PROCEDURES FOR DAMAGED TYRE/WHEEL ASSEMBLIES.
This procedure does not reduce or replace the need and importance of 24-hourly “cold” tyre pressure checks. Diamond recommends servicing tyres cold every week, minimum. This procedure is not to be used as a replacement for cold tyre pressure checks.
Do not reduce the pressure of a hot tyre that is to continue in service.
Hot tyres with pressures greater than 200% of the cold rated inflation pressure should be removed.
Casing Flat Spotting
Loaded tyres that are left stationary for any length of time can develop temporary flat spots. The degree of this flat spotting depends upon the load, tyre deflection and temperature. Flat spotting is more severe and more difficult to work out during cold weather. Occasionally moving a stationary motorcycle/ bicycle/ rickshaw/ wheel-barrow can lessen this condition. If possible, a motorcycle/ bicycle/ rickshaw/ wheel-barrow parked for long periods (30 days or more) should be jacked up to remove weight from the tyres. Under normal conditions, a flat spot will disappear by the end of the ride.
Protecting Tyres From Chemicals and Exposure
Tyres should be kept clean and free of contaminants such as oil, hydraulic fluids, grease, tar, and degreasing agents which have a deteriorating effect on rubber. Contaminants should be wiped off with denatured alcohol, then the tyre should be washed immediately with soap and water and inspected for surface damage such as blistering or softening. When motorcycle/ bicycle/ rickshaw/ wheel-barrow are serviced, tyres should be covered with a waterproof barrier. Tyre coatings or dressings: Diamond adds antioxidants and anti-ozonants to the sidewall and tread to help prevent premature cracking from ozone and weather exposure. There are many products on the market that are advertised to clean tyres and to improve appearance and shine. Since many of these may remove the antioxidants and anti-ozonants, we do not endorse any of them unless the tyres are to be used for display purposes only. Motorcycle/ bicycle/ rickshaw/ wheel-barrow tyres, like other rubber products, are affected to some degree by sunlight and extremes of weather. While weather-checking does not impair performance, it can be reduced by protective covers. These covers (ideally with light color or aluminized surface to reflect sunlight) should be placed over tyres when a motorcycle/ bicycle/ rickshaw/ wheel-barrow is tied down outside. Store all tyres away from fluorescent lights, electric motors, battery chargers, electric welding equipment and electric generators, since they create ozone which can have a deteriorating effect on rubber.
Condition of Wheel Assembly Floor Surfaces
Regardless of the excellence of any preventive maintenance program, or the care taken by the mounter and persons handling the motorcycle/ bicycle/ rickshaw/ wheel-barrow, tyre damage will certainly result if roads and other paved areas are in a poor condition or improperly maintained. Foreign object damage (FOD) is the most common cause for early removals. Chuck holes, cracks in pavement or asphalt, or stepoffs from pavement to ground can cause tyre damage. Pavement breaks and debris should be reported to shop personnel for immediate repair or removal. Another hazardous condition is the accumulation of loose material on paved areas and assembly floors. These areas should be kept clean of stones, tools, bolts, rivets and other foreign materials at all times. With care and caution in the assembly area tyre damage can be minimized.
Motorcycle/ bicycle/ rickshaw/ wheel-barrow Tyre Conductivity
Tyres dissipate some static electricity in service but this conductivity will change with the cleanliness of the tyre surface, atmospheric conditions and road surface. Since this discharge rate is variable and not very controllable, the tyre cannot be counted on to dissipate static electricity. If there is any question about static charge build-up, the motorcycle/ bicycle/ rickshaw/ wheel-barrow must be taken care of by mechanical means.
Static electricity can spark, initiating a fire. Do not rely on tyres to dissipate static electricity.
Tyre Balancing and Vibration/ Wobbling
It is important that motorcycle/ bicycle/ rickshaw/ wheel-barrow wheels and tyres be as well balanced as possible. Vibration, shimmy, or out of balance is a major complaint. However, in most cases, tyre balance is not the cause.
Other factors affecting balance and vibration are:
• Out of balance rims
• Installation of wheel assembly before full tyre stretch
• Improperly installed tube
• Use of non motorcycle/ bicycle/ rickshaw/ wheel-barrow tubes
• Poor rim alignment
• Bent wheel
• Incorrect balancing of wheel assembly