Retread

Key takeaways

Retread belongs to science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Retread to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Retread from memory before moving on to harder problems.

Reference excerpt

Retread (also known as recap or remold) is a re-manufacturing process for tires that replace the tread on worn tires. Retreading is applied to casings of spent tires that have been inspected and repaired. It preserves about 90% of the material in spent tires and the material cost is about 20% compared to manufacturing a new one.

Applications

United States Some applications for retreaded tires are airplanes, racing cars, buses and delivery trucks. Use of retreaded tires was common historically, but as of 2008, it was seldom used for passenger vehicles, mainly due to discomfort on the road, safety issues and cheaper tire brands surfacing on the market. About 17.6 million retreaded tires were sold in North America in 2006.

Process

There are two main processes used for retreading tires, called Mold Cure and Pre Cure. Both processes start with the inspection of the tire, followed by non-destructive inspection method such as shearography to locate non-visible damage and embedded debris and nails. Some casings are repaired and some are discarded. Tires can be retreaded multiple times if the casing is in usable condition. Tires used for short delivery vehicles are retreaded more than long haul tires over the life of the tire body. Casings fit for retreading have the old tread buffed away to prepare for retreading.

Material cost for a retreaded tire is about 20% that of making a new tire. About 90% of the original tires by weight is retained in retreaded tires. A 1997 study estimates that then current generation of commercial vehicles tires to last up to 600,000 miles (970,000 km) if they're retreaded two to three times.

Pre cure Previously prepared tread strip is applied to tire casing with cement. This method allows more flexibility in tire sizes and it is the most commonly used method, but results in a seam where the ends of the strip meet.

Mold cure Following a thorough quality inspection, the worn tire tread is removed from the casing by buffing. Raw rubber is then applied to the tire casing and it is then placed in a mold where tread is formed. A dedicated mold is required for each tire size and tread design. This tread application method is very similar to that of the new tire manufacturing process.

Bead to Bead molding In this subtype, retreading is also applied to the side walls. These tires are given entirely new branding and stamps.

Regulations Some jurisdictions have regulations concerning tire retreading.

Europe In Europe all retreads, by law, must be manufactured according to EC Regulation 108 (car tires) or 109 (commercial vehicle tires). As part of this regulation all tires must be tested according to the same load and speed criteria as those undergone by new tires. The Land Fill Directive of 1999 banned tires in landfills in 2003, and banned shredded tires in 2006.

United States The Department of Transportation requires marking of a "DOTR number" which shows the name of the retreader and when it was retreaded.

Safety The United States National Highway Traffic Safety Administration recognizes the public perception that retread tires frequently used by heavy vehicles are less safe than new tires as evidenced by tire debris frequently found on highways. The NHTSA is continuing research to determine the proportion of tire debris from retreads in comparison to new tires. Additionally, the NHTSA is researching the cause of tire failure and the crash safety problem posed by tire failures. Federal Executive Order 13149, signed by President Bill Clinton supports the use of retread tires for economic and environmental efficiency by requiring federal vehicles to use retread tires after original factory equipped tires become non serviceable, but only when "such products are reasonably available and meet applicable performance standards".

Environmental impact Retread tires in service lower the volume of raw materials required for the manufacturing of a new tire. This includes a pronounced reduction in the use of oil. In fact, the US EPA estimated a greater than 75% savings in oil used for a retread as compared to a new tire. This also means significant reductions in greenhouse gas emissions. A car tire has 40% natural rubber and 60% oil based rubber, a retreading of tires will reduce the need for natural rubber significantly. In addition to reducing the amount of raw materials extracted, retread tires also minimize the amount of waste that ends up in landfills. The latest figures by the US EPA indicate that over 11.2 M waste tires were dumped into the U.S. municipal solid waste stream. To understand this figure, it is equivalent to lining up passenger tires tread to tread from roughly Los Angeles to San Diego or Philadelphia to Washington DC. Because a retread tire prevents the need for manufacturing a new tire, significant environmental benefits are achieved.

Illustrations

Worked examples

Example 1 — a first encounter with Retread

Start with the simplest possible case. Write down what Retread claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Retread before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Retread ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Retread

In research: Retread appears in science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Retread in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Retread is common in secondary-school and first-year university syllabi. It links to neighbouring topics Recycling, Tires, so understanding it makes those chapters shorter.
In everyday life: Look for Retread outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

How to study Retread in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Retread means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Retread out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Retread in simple terms?

Retread (also known as recap or remold) is a re-manufacturing process for tires that replace the tread on worn tires. Retreading is applied to casings of spent tires that have been inspected and repaired.

Why does Retread matter?

Because it connects several science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Retread?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Retread.