---
title: "What is a Car tire made of?"
description: "Several different rubber compounds reinforced with steel and textile cord — closer to a composite than to rubber. Every component, the material it uses, and the cons"
url: https://atoneplace.net/made-of/tire/
site: "At One Place"
---

# What is a Car tire made of?

**What is a Car tire made of?: Several different rubber compounds reinforced with steel and textile cord — closer to a composite than to rubber.**

Tires were white or pale grey until carbon black was added around 1910 — first as a cheap filler, then because it multiplied tread life several times over. The modern equivalent story is 6PPD, the antiozonant that stops sidewalls cracking: research published in 2020 identified its oxidation product 6PPD-quinone, washed off roads in runoff, as the cause of long-unexplained mass die-offs of coho salmon in the US Pacific Northwest, and replacements are now being actively sought. Tire rubber also ages chemically whether or not it is driven on, which is why the four-digit DOT week-and-year code on the sidewall matters on a caravan or a spare that has done almost no miles.

## Component by component

*Every material is a choice, and the third column is the constraint that drove it.*

| Part | Material | Why that material |
| --- | --- | --- |
| tread compound | natural rubber blended with styrene-butadiene and polybutadiene, loaded with carbon black and silica | Silica cuts rolling resistance while keeping wet grip, a trade-off that carbon black alone cannot win; carbon black gives abrasion resistance. |
| belts | brass-plated steel cord, in two crossed layers under the tread | Steel keeps the tread flat against the road under cornering load; the brass plating is there so the rubber bonds chemically to the wire. |
| carcass plies | polyester or rayon cord, radial to the direction of travel | The cords carry the inflation pressure while letting the sidewall flex, which is what makes a radial tyre ride better than a cross-ply. |
| bead | bundled high-tensile steel wire wrapped in rubber | It is the part that cannot stretch, so the tyre stays clamped on the rim against several tonnes of force. |
| inner liner | halobutyl rubber | Butyl is far less permeable to air than natural rubber, which is what allows a tubeless tyre to hold pressure for months. |
| antidegradants | waxes and para-phenylenediamine antiozonants such as 6PPD | Ozone cracks stretched rubber within months; these migrate to the surface and are sacrificially attacked instead. |

## Other cars and driving objects

- [Car battery](https://atoneplace.net/made-of/car-battery/) — Lead and lead dioxide plates in dilute sulfuric acid, in a polypropylene case — mostly lead, by weight.
- [Airbag](https://atoneplace.net/made-of/airbag/) — A coated nylon bag inflated by a small solid-propellant gas generator in about thirty milliseconds.
- [Brake pad](https://atoneplace.net/made-of/brake-pad/) — A friction compound of fibres, fillers and resin, moulded and bonded onto a steel backing plate.
- [Windshield (windscreen)](https://atoneplace.net/made-of/windshield/) — Two sheets of ordinary glass laminated to a tough plastic interlayer, which is what stops it falling out.
- [Spark plug](https://atoneplace.net/made-of/spark-plug/) — A ceramic insulator carrying a centre electrode of nickel, platinum or iridium inside a steel shell.
- [Seatbelt](https://atoneplace.net/made-of/seatbelt/) — Woven polyester webbing designed to stretch a controlled amount, plus a locking retractor and a pyrotechnic pretensioner.

## Common questions

### What is a Car tire made of?

Several different rubber compounds reinforced with steel and textile cord — closer to a composite than to rubber.

### What is the tread compound of a Car tire made of?

Natural rubber blended with styrene-butadiene and polybutadiene, loaded with carbon black and silica. Silica cuts rolling resistance while keeping wet grip, a trade-off that carbon black alone cannot win; carbon black gives abrasion resistance.

### What is the belts of a Car tire made of?

Brass-plated steel cord, in two crossed layers under the tread. Steel keeps the tread flat against the road under cornering load; the brass plating is there so the rubber bonds chemically to the wire.

## Related pages

- [Car battery](https://atoneplace.net/made-of/car-battery/)
- [Airbag](https://atoneplace.net/made-of/airbag/)
- [Brake pad](https://atoneplace.net/made-of/brake-pad/)
- [Windshield (windscreen)](https://atoneplace.net/made-of/windshield/)
- [Spark plug](https://atoneplace.net/made-of/spark-plug/)
- [Seatbelt](https://atoneplace.net/made-of/seatbelt/)
- [Pencil](https://atoneplace.net/made-of/pencil/)
- [Tennis ball](https://atoneplace.net/made-of/tennis-ball/)
- [Banknote](https://atoneplace.net/made-of/banknote/)
- [Golf ball](https://atoneplace.net/made-of/golf-ball/)
- [Paper](https://atoneplace.net/made-of/paper/)
- [Glass](https://atoneplace.net/made-of/glass/)

## Sources

- Typical range compiled from manufacturer specifications — At One Place (/about/)