Radial Tyre Production

Radial tyre manufacturing starts with many kinds of raw materials, pigments, chemicals, some 30 different kinds of rubber, cord fabrics, bead wire, etc. The process begins with the mixing of basic rubbers with process oils, carbon black, pigments, antioxidants, accelerators and other additives, each of which contributes certain properties of the compound. These ingredients are mixed in giant blenders called Banbury machines operating under tremendous heat and pressure. They blend the many ingredients together into a hot, black gummy compound that will be milled again and again.

The cooled rubber takes several forms. Most often it is processed into carefully identified slabs that will be transported to breakdown mills. These mills feed the rubber between massive pairs of rollers, over and over, feeding, mixing and blending to prepare the different compounds for the feed mills, where they are slit into strips and carried by conveyor belts to become sidewalls, treads or other parts of the tyre. Still another kind of rubber coats the fabric that will be used to make up the tyre's body. The fabrics come in huge rolls, and they are as specialized and critical as the rubber blends. Many kinds of fabrics are used: polyester, rayon or nylon. Most of today's passenger tyres have polyester cord bodies.

Another component, shaped like a hoop, is called a bead. It has high-tensile steel wire forming its backbone, which will fit against the vehicle's wheel rim. The strands are aligned into a ribbon coated with rubber for adhesion, then wound into loops that are then wrapped together to secure them until they are assembled with the rest of the tyre. Radial tyres are built on one or two tyre machines. The tyre starts with a double layer of synthetic gum rubber called an inner liner that will seal in air and make the tyre tubeless.

Next come two layers of ply fabric, the cords. Two strips called apexes stiffen the area just above the bead. Next, a pair of chafer strips is added, so called because they resist chafing from the wheel rim when mounted on a car. The tyre building machine pre-shapes radial tyres into a form very close to their final dimension to make sure the many components are in proper position before the tyre goes into the mold.

Now the tyre builder adds the steel belts that resist punctures and hold the tread firmly against the road. The tread is the last part to go on the tyre. After automatic rollers press all the parts firmly together, the radial tyre, now called a green tyre, is ready for inspection and curing.

The curing press is where tyres get their final shape and tread pattern. Hot molds like giant waffle irons shape and vulcanize the tyre. The molds are engraved with the tread pattern, the sidewall markings of the manufacturer and those required by law. Tyres are cured at over 300 degrees for 12 to 25 minutes, depending on their size. As the press swings open, the tyres are popped from their molds onto a long conveyor that carries them to final finish and inspection.

If anything is wrong with the tyre it is rejected. Some flaws are caught by an inspector's trained eyes and hands; others are found by specialized machines. Inspection doesn't stop at the surface. Some tyres are pulled from the production line and X-rayed to detect any hidden weaknesses or internal failures. In addition, quality control engineers regularly cut apart randomly chosen tyres and study every detail of their construction that affects performance, ride or safety.

This is how all the parts come together: the tread and sidewall, supported by the body, and held to the wheel by the rubber-coated steel bead. But whatever the details, the basics are fundamentally the same: steel, fabric, rubber, and lots of work and care, design and engineering.

Basic Ingredients To Make A Tyre

Fabric steel, nylon, aramid fiber, rayon, fiberglass, or polyester (usually a combination, e.g., polyester fabric in the body plies and steel fabric in the belts and beads of most radial passenger tyres)

Rubber natural and synthetic (hundreds of polymer types)

Reinforcing chemicals -- carbon black, silica, resins

Anti-degradants -- antioxidants, ozonants, paraffin waxes

Adhesion promoters -- cobalt salts, brass on wire, resins on fabrics

Curatives -- cure accelerators, activators, sulfur

Processing aids -- oils, tackifiers, peptizers, softeners

A P195/70R14 all-season passenger tyre, the most popular size, weighs about 9.5 kg’s and has approximately:

5 lbs. of 30 different types of synthetic rubber

4 lbs. of 8 types of natural rubber

5 lbs. of 8 types of carbon black

1 lb. of steel cord for belts

1 lb. of polyester and nylon

1 lb. of steel bead wire

3 lbs. of 40 different kinds of chemicals, waxes, oils, pigments, etc.

Typical percentages of the Synthetic Rubber and Natural Rubber rubber mix in various types of tyres:

Passenger Tyre 55% - 45%
Light Truck Tyre 50% - 50%
Race Tyre 65% - 35%
Off-highway Tyre 20% - 80% (giant earth mover)

Procedure To Repair A Tubeless Tyre

The following items are required to repair a tubeless tyre with mushroom patches, which is recommended by most of the tyre manufacturers.

Mushroom patches A3 & A6 size (Schradder or Tip Top)
Solution or cement recommended by the patch manufacturer
Drilling machine of 3200 RPM
Drilling Bit 3mm and 6mm
Buffing tool for buffing the tyre inner liner
Sticher
Marking chock
Probe to check the angle of incertion of the nail
Soap water
Cotton waste
Cutting plier and nose plier
Screw driver medium size minus and plus

First inspect the tyre and mark the area from outside where the nail or object has penetrated. Remember that the tyre can be repaired only on the tread area and not on the side wall. The illustration shown below shows the repairable area on the tyre

Remove the tyre from the rim with out removing the nail or object, which has penetrated the tyre.

Inspect the tyre from inside and check for any internal damages which might have been caused due to the insertion of the nail or object.

Mark the tyre from inside also to identify it later. After inspecting the tyre, if the nail or object has penetrated the repairable area, pull out the nail and put the probe into the hole from where the nail has been removed to check the angle of insertion.

After checking the angle of insertion, check which size of the patch has to used, the 3mm or 6mm. Once that has been identified drill the tyre with the correct drill bit.

Keeping in mind the angle of insertion of the nail, drill the tyre from outside first and then from inside till the steel belts have been shaved off so that they don't cut the stem of the mushroom patch.

Buff the inner liner of the tyre as per the patch size (3mm or 6mm) so that the patch can stick on the tyre properly or in general words just rough the liner so that the patch can have a grip on the tyre when stuck with the solution.

Spread the solution or cement on the area where the patch has to be stuck, and let it dry for a minute. Insert the mushroom patch from inside and pull it out from the plier so that it sticks to the tyre liner.

Stich the patch on to the tyre so that there is no air bubble on the sticking area, which could result in a leakage.

Stich the patch from the center to the side and then from center to top and bottom.

Leave it to dry for 1-2 minutes.

Fit the tyre on the rim and inflate it to the recommended air pressure. Cut the extra stem of the patch to the tread level on the tyre.

Spray the soap solution to check for leakage. Make sure to balance the rim after the repair.

The tyre is now ready for use. A speed rated tyre can be repaired 6 times.

What Customers Should Know About Radial Tyres and Their Maintenance

Many motorists either don’t know how to get the best service out of tyres or don’t take the time and effort to make it happen, it is important that they be educated on how to maintain and care for their tyres. This is true for all tyre constructions whether they are radial or bias tyres. Specific areas where customer education is recommended are as follows:

Radial – feel of the road

Most motorists have either owned radials or are familiar with them through the experience of others. However, first time radial buyers should be told to expect a new feel on the road, a feeling of firmness at slower speeds. This is characteristics of radials because of the stiffer belts. This firmer feel of the road and faster steering response becomes an asset at street and highway speeds, adding to the performance characteristics that make radials so popular.

Inflation

When properly inflated and under load, a radial tyre has a distinctive bulge in the sidewall. This is normal for radials, but makes it very difficult to judge visually whether or not a radial tyre is properly inflated. Customers should be cautioned not to add air to make a radial tyre look as inflated as a bias ply tyre.

However, they should not be misled into accepting almost any degree of bulge as being normal. The only way to be sure a radial tyre is inflated correctly is to check tyre pressure regularly with a reliable gauge, following the vehicles manufacturers specification or after consulting a tyre professional. For futher information on this subject go through the “importance of checking air pressure”.

Rotation

Tyres should be inspected periodically to determine overall wear and any irregular wear pattern development. Rotating tyres as per the recommendations of a tyre professional can often deliver more uniform tyre wear and longer tyre life. For futher information on this subject go through the “tyre rotation” chart.

Balancing

A balanced tyre, while improving riding comfort, also lowers the constant change in the tyre load (due to bounce). The constant bouncing of tyres leads to wear of steering and suspension parts, as would worn shocks, and could lead to misalignment conditions. A majority of vibration complaints are a result of improper balance. For futher information on this subject go through the “balancing & its terminology” chart.

Alignment

Proper alignment is mandatory for even tread wear and precise steering. The moderate cost of a front-end alignment can more than pay for itself in tyre mileage, performance and comfort. The customer should be advised to check front tyres periodically for uneven wear or changes in handling or steering response, which indicate misalignment. For futher information on this subject go through the “alignment & its terminology “ chart.