1Historically, wheels were made of metal or wood.
2With the invention of air-filled car tires in the early part of the 20th Century,
3the ride was revolutionized.
4The inflated rubber tires could better absorb the bumps on the road,
5and the addition of tread gave the invention serious traction.
6Car tires have come a long way in the last century.
7The modern summer tire is made of 10 to 15 different components
8which include natural and synthetic rubber, chemical additives, and carbon black, a pigment.
9Giant blenders mix these ingredients under heat and tremendous pressure.
10There are various formulations for different parts of the tire.
11In each case, the result is gummy rubber dough
12which machinery then rolls into sheets to wait further kneading and processing.
13Polyester fabric unrolls into a machine called a calender.
14The calender's equipped with rollers that apply warm rubber to both sides of the fabric.
15This produces a rubberized fabric that will be used to reinforce the tire.
16This fabric ply is kneaded because rubber alone isn't sturdy enough to make a tire.
17Numerous cotton cords now spin off bobbins simultaneously.
18Machinery pulls them onto the warm rubberized fabric.
19They land on a bit of an angle and adhere.
20This cording creates channels that provide pathways for venting air during the actual tire building.
21Making rubber for tread requires three different rubber formulations.
22Extruders shape the three streams of rubber,
23and then they enter a die that forms them into one.
24Many paint rollers apply different colored stripes.
25It's a coding system for identification of the ingredients during processing.
26To avoid tension, the system creates slack in the feed.
27A blade slices the tread rubber to length.
28Next, many steel cables uncoil at once to make the bead -
29the part of the tire that gives it the strength it needs to stay on the wheel rim.
30Machinery arranges the cables in the desired configuration and encases them in rubber.
31More equipment rolls the bead material into hoops sized to fit the wheel rim.
32They're now ready to build the tire.
33Using a special rotating drum, a worker arranges the two bead hoops on it.
34Next up is an airtight piece of rubber that will act as an inner tube followed by the corded ply.
35Inflated bladders roll the rubber around the bead on both sides and then retract.
36A surfer applies side walls to the beads.
37Little rollers fold the side walls over the beads.
38This completes the inner part or skeleton of the tire.
39They assemble the outer layer separately, beginning with strips of rubber embedded with steel cord.
40The system wraps this rubber around a second tire-building drum.
41Next up are narrow strips of rubber ply.
42The computerized system winds them with just the right amount of tension for a graduated effect.
43They're now ready for the last layer, the tread rubber.
44Machinery applies it to the ply.
45It's time for the two tire fabrications to become one.
46A transfer ring collects the assembly and transfers it to the inner part.
47Compressed air inflates the tire to shape it, and all the sticky layers adhere together.
48The machine rolls the edge of the tread rubber over the side walls.
49They now have what's known in the industry as a green tire,
50an uncured tire without tread pattern.
51Next, it's into a mold to bake and shape the tire.
52The two parts of the mold come together like a waffle iron.
53Inside, hot steamy bladders expand to shape the tire and transfer the tread pattern to it.
54This specific tread pattern is designed for summer tires.
55This cutout of a car tire demonstrates how all the layers have been fused together.
56The time in the hot pressurized mold has caused the rubber to vulcanize,
57a chemical reaction that transforms it from a weak and sticky substance to one that's strong and elastic.
58A worker trims excess rubber.
59After final inspections confirm the tire's shape is uniform and geometrically correct,
60the tire is ready for shipment.
61It's time for the rubber to hit the road.