Today's Truck Tires: The Inside Story

today's radial truck tires are masterpieces of Applied Technology they have to start stop carry and turn thousands of pounds of truck and cargo at speeds up to 75 miles per hour and yet we also expect them to last for hundreds of thousands of miles and we expect to retread them a form of recycling to make them last even longer how can a tire do this what gives it the extraordinary strength and staying power it needs to find out we'll look at what's inside it then we'll see what goes into the making of a modern truck tire we'll start at the outside the tread of course is a thick layer of rubber with a tread pattern molded into it the rubber is application-specific that means each rubber compound is chosen for a specific combination of qualities like fuel economy wet traction and cut in chip resistance treads are often a blend of natural and synthetic rubber because each has unique desirable performance characteristics different additives polymers and other components provide strength and resiliency along with resistance to wear and heat all are combined then cured in moulds at high temperatures changing the materials bonding them together chemically and forming the tread the tread pattern is designed to optimize traction and where it must grip the road wet or dry because the tire controls the traction forces for the truck but even a tread isn't as simple as it looks when we cut through it we see different shades of color in the rubber why is that well in most Bridgestone tires two different layers of trend rubber are used each has a slightly different color because each has a slightly different composition the top layer called the cap is designed for long slow even wear the layer below the base is designed to shield the casing from heat generated as the tire rolls down the road heat is the enemy of tire casings shortening their life because retread ability is so important for tires heat must be controlled and that's why cap and bass construction is so important as we dig further we find a layer of rubber called the under tread the under tread provides additional protection for the casing and also helps form the bond between the tread and belts different thicknesses of under tread are used depending on the amount of off-highway service or re grooving required from this point on we're looking at what we call the casing this is the part of the tire that gets retreaded once the original tread is worn away below the under tread we find layers of steel cables and rubber there are usually three or four of these belts and a body ply in a Bridgestone truck tire the job of the belts is to hold the tread flat against the road without them the casing would take on an inner tube like shape footprint pressure would be uneven and the result would probably be poor traction for stability Plus rapid and irregular wear steel belts also help tires resist penetration by males and other road hazards the cords in each belt run at different angles that distributes forces evenly and provides great strength like the rubber the steel cord is application-specific different alloys different tensile strengths along with different ways of winding the cords are used to produce exactly the performance characteristics needed in each part of the tire both steel and rubber are specially made to help them bond to each other steel is treated with the metal cobalt and brass formulations to help the steel and rubber bond tightly the rubber that surrounds the steel cords maintains cord spacing and seals out moisture that could cause rust which could break the bond with the rubber and steel adds enormous strength long ago a 14 ply rated tire needed 14 cotton layers today just three or four steel reinforced layers in the belt package plus one layer of body ply cords do the same job beneath the belts we find another combination of rubber and steel we notice that these steel cords run at right angles to the tread and they run radially down the sidewalls of the tire it is this chord direction that gives the radial tire its name if you draw a line from the center of the tread to the bead a radius you see that these radial lines match the steel chords hence the name radial tire as a group these radial chords are called the body ply and run all the way around the tire a typical truck tire has approximately 1200 of these each cord runs from bead to bead as it does it forms part of the sidewall the sidewall does most of the flexing as the tire rolls sidewalls flex about 500 times per mile and hundreds of millions of times over the tires life by flexing and changing shape the steel together with the compressed air inside the tire helps absorb shocks from uneven road surfaces the sidewalls transmit steering driving and braking forces from the wheels to the tread as well as forces from the road to the suspension system although sidewalls don't get the kind of wear treads do they are exposed to the elements so sidewall rubber uses special compounds and special additives to protect it from UV light weather aging and curbing as the body ply cords continue toward the beat of the tire they suddenly turn completely around the bead and start back up the sidewall this is called the ply turn up because the cords actually turn up and head back the opposite direction inside the turn up is a band of many strands of steel wire called the bead bundle the body ply wraps around it the space between body ply and bead contains several different kinds of rubber and fillers each is formulated to add strength while giving the area stress resistance the bead is the edge of the tire you might say the place where the tire makes contact with the wheel the bead creates a tight seal between tire and wheel since the entire inside of a tire is open it is the compressed air that forces the beads against the wheel flanges sealing in the air there's also a small additional component made of wire or wire and fabric called a chafer it covers the bead bundle and ply turn-up it provides protection against damage that might occur when the bead is forced over the edge of the wheel and as the bead moves against the rim flange also protecting the bead area from abrasion is a tough rubber compound that helps make beads more rigid for further damage protection but we have one more component to go air molecules are tiny and can literally diffuse through rubber causing the tire to lose pressure to slow this the inside of the tire is covered with what is called an inner liner this is yet another layer of rubber though it's thin the inner liner actually has two or three separate layers one layer prevents air and moisture from passing through the other helps it bond to the casing ply to more rubber compounds each with a specific job still even with the best inner liner a tire can lose 2 psi per month another reason to check inflation pressures regularly we've seen all the major components of a modern radial tire now how is a tire like this actually produced to find out we'll visit a Bridgestone Firestone truck tire factory as we've learned the basic materials are rubber and steel about 70% of the rubber and a truck tire is natural rubber which comes from the sap of rubber trees about 30% is synthetic made from petroleum and other materials specially made steel wire of a variety of types and thicknesses is used in the belts body ply and beads and there are several specific additives used to help in processing curing and strengthening rubber and in protecting tires against air sunlight and ozone silica which is related to common sand can be added to reduce heat and rolling resistance to improve fuel economy different grades of carbon black can also create different performance characteristics and many secret ingredients can have almost magical effects on how a tire performs koala control begins with the incoming materials every batch of rubber every bit of steel every additive even the water is tested first by the supplier to make sure it meets Bridgestone specifications then it's tested again by Bridgestone Firestone technicians to verify its quality and as materials go through the process they are tested repeatedly to make sure they will perform properly in the finished product both chemical and physical properties are checked we need not only the right materials but the right strength flexibility size and other characteristics nothing can be used to build a tire until it has been tested and approved each of the many different rubber compounds is mixed separately careful weighing assures precise formulations at this stage though rubber is tough stuff to mix a batch you need powerful mixers these Banbury mixers have 4,000 horsepower motors enough to power more than 10 semis and can handle half a tonne of rubber at a time once rubber leaves the Banbury it is squeezed between heated rolls called Mills it comes out of the mills in sheets which may be put back into the Banbury again and again depending on specifications set by the chemical engineers and this has to happen for each of the different compounds used to make a tire Steel is used to make body plies and belts multiple strands of wire already wound into cords must be aligned and bonded to rubber nearly a thousand strands pass through guides before being sandwiched with rubber in a machine called a calendar powerful heated rollers press rubber onto and between the cords the result is a sheet of steel reinforced rubber these sheets are then cut at the precise angles needed to make body plies and belts quality control continues in every part of the process throughout the plant giant poster light charts provide operators with checkpoints for each step in manufacturing every critical step is checked and verified before work can proceed the airliner another sheet like material is also made using a calendar but it contains no steel and the other thicker wire will be coated with rubber and wound into sturdy rings that become the beads many rubber components are made by extrusion the largest of these extrusions is the tread but many smaller ones are used in making parts of sidewalls and fillers up to now we've been making parts that will be assembled to make the actual tire a person called a tire builder assembles these parts using a tire assembly machine this is the heart of the tire manufacturing process every component is identified and tracked using barcodes specifications and computers at each building machine make sure only the right components get used to make what happens as clear as possible we'll use animation to simplify and slow down the process basically the parts are laid out on the surface of a big drum we begin with the wire bands that form the beads the sidewalls go on next then the inner liner is added followed by the chafers and body ply with the exception of beads each of the components has to be matched and forend and spliced together but it still doesn't look much like a tire that's where the magic of the tire assembly machine comes in a bladder inside this new tire is inflated then the belts are put into place and finally the tread is attached bladders on each side inflate pushing components into the characteristic tire shape the sidewalls and body ply ends are folded around the beads and pressed firmly against the sides of the tire a barcode is applied identifying this tire the operator who built it and every component in it so any irregularity can be tracked back to its source special rollers press all the components together a process called stitching because the rubber is still uncared the various parts are soft and stick together easily the result is something that looks remarkably like a tire but it's not cured so we call it a Green tire we still have to create the tread pattern and sidewall design and vulcanize the components that's done by giant heated presses that contain the molds the Green tire is placed inside the mould and pressure is applied from the inside as the mold closes the tread segments slide toward the tire forming the tread pattern and shaping and finishing the outside inside the air cavity of the tire a rubber bladder sort of like a big inner tube inflates to press the inside of the tire against the mold molds are incredibly precise and very expensive fifty to seventy thousand dollars as much as a small house and you need separate molds for every tire size and every tread pattern for popular tire designs you might need dozens even hundreds of molds Green tires are heated at precisely programmed temperatures and pressures for precisely controlled time periods high-pressure steam provides the heat and sometimes is also used to generate electricity reducing both power bills and pollution the process is called curing or vulcanization it bonds the components of the tire together forming chemical links between rubber molecules curing changes rubber from something sticky and soft and summer and stiff and hard and winter into a tough material that provides remarkably predictable performance year round once the tire is cured you might think it's ready to use but there are a few more things to be done quality control which has been continuous throughout manufacturing now looks at the finished product x-ray machines see steel cords inside the rubber to make sure they are properly aligned and properly spaced any tire that doesn't meet specifications is scrapped and may be recycled as clean-burning fuel or may be made into flooring or even asphalt in addition each tire is checked for balance this machine marks the light static balance point of each tire with a yellow dot this makes achieving initial static balance easier when you mount a new tire again if the tire is outside specifications it is scrapped some tires are also marked with a radial force variation mark like the static balance mark this helps reduce ride disturbance by helping you mount the tire for minimum vibration and skilled operators examine each tire by sight and touch for quality they give each tire the final okay to go to you tread patterns and sizes are sorted labels are applied and the tires are sent to warehouse areas for shipment at this plant a robotic warehouse system stacks stores and retrieves finished tires to fill orders without requiring any human labor and quality control still has intended Bridgestone Firestone technicians routinely pol random samples for testing tires are tortured on test drums punctured by hydraulic rams cut up then examined with microscopic precision technicians compare final products to specifications looking for variations that could diminish performance tread life or retread ability it can take weeks to test the tire but it's an important job because it assures consistent quality and tires aren't tested only in the laboratory at the Bridgestone Firestone Texas proving ground tires are tested a variety of ways including running on a 7 and 3/4 mile / track and put through tests designed to simulate the kind of abuse real tires get in the real world if the tire is a new design it will also be given extensive field trials before being released to customers only when a bridge stone or Firestone Tire passes all these tests is it ready for you and even then field engineers and sales representatives monitor the performance of tires on customer vehicles paying special attention to anything out of the ordinary the results are some of the finest truck tires available for virtually every application and every vocation truck tires with incredibly long life extraordinary traction and handling and the provide low cost per mile by maximizing retread ability with good maintenance and careful retreading some of these tire casings have provided their owners with over 1 million miles of service so why do Bridgestone Firestone truck tires deliver such outstanding performance as we've seen it's the way they're made the advanced methods and materials they're made of and the people who make them you

Channel: Bridgestone Commercial

Views: 838,921

Keywords: bridgestone, firestone, truck tire, tread design, retread, bandag, tire casing

Id: wA0dX-phO2Q

Length: 18min 55sec (1135 seconds)

Published: Fri Oct 19 2012