Tires are probably the single most important component of a car, yet also the most overlooked. Many vehicle owners ignore the fact that tires are the only thing in contact with the ground, and the quality and type of tire will determine how well the vehicle grips the road and stops. While some aspects of tires have not changed in a century (they are still air filled round rubber donuts), other tire designs are cutting edge. With that in mind, let’s take a look at how modern tires are made.

First, a technician will seat a metal hoop onto the tire machine. This is called the bead, and is the part of the tire that seals to the wheel, keeping the air inside. Then the tech applies the inner liner to a steel cylinder roughly the shape and size of the tire being made. On top of the liner, the tech adds layers of ply. Ply looks like simple rubber, but just rubber is not strong enough to deal with the demands of modern vehicles. Ply is actually a synthetic fiber coated in rubber, to offer a light weight, yet strong and durable solution. The tech adds at least two plys for modern tires, making sure there are no air bubbles, and the layers are in proper contact. Finally, the metal bead is applied and the liner and plys wrapped over the edge.

Then the technician makes the sidewall. Rubber is laid onto the plys, stitched, and the air removed. This is a critical step. Remember the Ford Explorer/Firestone fiasco about 15 years ago? The tires were blowing out due to improper sidewall stitching techniques, so the tech makes sure to get it right here. Interesting fact: if you select run-flat tires, the sidewall will be much thinker in case of a loss of air pressure. This creates a safety margin for the driver, but also a weight penalty and reduction of gas mileage.

What we have now is called a “tire carcass.” It is obviously the wrong size and lacking tread, so the tech places it on the tread winder. Tread is applied by a robot in long rubber sheets, and essentially completes the assembly of the tire. Then the tech places the tire carcass into a mold. Massive pneumatic pressure expands a bladder that forces the tire against a mold of the tire’s tread and sidewall markings. The tire is then baked for about 10 minutes, and the tread and shape becomes permanent.

Check out the video below to see the process:

5 Responses to Round Rubber Donuts: How Tires Are Made

  1. Hey- thanks for this info! I’m actually looking to get into tire repair and hopefully one day own my own used tire shop, so I found this info to be very helpful!

  2. The tire size really does not play a part in what PSI you need. The vehicle manufacturer has a recommended PSI rating and that would be a good starting point. Depending upon what sort of comfort you are looking for, you can either increase or decrease the pressure but never going under the recommended PSI for the vehicle or going over the max PSI of the tire.

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