Why Do Rubber Air Springs Fail from Ozone Cracking? How Wuxi ChuncoTech Rubber Protects Suspension Components

In our last article, “Why Do Rubber Fenders Lose Energy Absorption Capacity Over Time? How Wuxi ChuncoTech Rubber Maintains Long-Term Performance” , we solved fender hardening problems. Today, we address a common failure mode for rubber air springs in buses, trucks, and rail vehicles: ozone cracking. If you have ever asked “why do my air springs have cracks after a few years of outdoor service,” ozone is the culprit. Air springs are mounted under vehicles, exposed to the atmosphere. Ozone from the environment (and from electric motors) attacks natural rubber and NBR compounds, creating surface cracks. Once cracks form, they propagate under flexing, leading to air leaks and sudden failure. At Wuxi ChuncoTech Rubber, we manufacture ozone-resistant rubber air springs using EPDM and CR compounds that do not crack. Here is what causes ozone cracking—and how our air springs stay flexible and leak-free.

The Ozone Cracking Mechanism: Surface Attack Under Stress

Ozone (O₃) is present in the atmosphere at low concentrations (0.01–0.05 ppm). But it is highly reactive with unsaturated rubber compounds like natural rubber (NR), styrene-butadiene rubber (SBR), and nitrile rubber (NBR). When the rubber is under stress (flexing, tension, compression), ozone attacks the strained polymer chains. Cracks form perpendicular to the stress direction. These cracks grow with time, penetrating the rubber thickness. When the crack reaches the cord reinforcement, the air spring leaks.

Why are air springs vulnerable?

• Constant flexing: The bellows flexes with every bump, creating stressed surfaces.

• Outdoor exposure: Air springs are under the vehicle, exposed to ozone.

• Standard NR/NBR compounds: Most air springs use natural rubber for its excellent dynamic properties—but NR is highly ozone-susceptible.

How Wuxi ChuncoTech Rubber Prevents Ozone Cracking

EPDM bellows for ozone resistance: We offer EPDM-based air springs for non-oil applications. EPDM is inherently ozone-resistant—it does not crack. The trade-off: lower oil resistance than NR/NBR.

CR (chloroprene) for balanced properties: For applications requiring moderate oil and ozone resistance, CR provides a balance. It is more ozone-resistant than NR but less than EPDM.

Ozone-protected NR compounds: Where NR's dynamic properties are essential, we add antiozonants (6PPD, IPPD) and wax bloom to protect the surface. The wax migrates to the surface, forming a physical barrier against ozone.

Protective cover layer: We can add a thin EPDM cover layer over an NR bellows. The EPDM faces the ozone; the NR provides dynamic properties.

Real-World Result: Transit Bus Air Springs Last 8 Years

A transit bus fleet was replacing air springs every 3 years due to ozone cracking. The buses operated in a smoggy city with high ozone levels. They switched to Wuxi ChuncoTech Rubber EPDM air springs. After 8 years of continuous service, no ozone cracks were visible. The fleet saved over $100,000 in replacement costs.

Your Ozone-Resistant Air Spring Partner

Wuxi ChuncoTech Rubber manufactures rubber air springs with ozone resistance for buses, trucks, and rail vehicles. We offer EPDM (maximum ozone resistance), CR (balanced ozone/oil resistance), antiozonant-protected NR (dynamic properties), and protective EPDM cover layers. As part of our automotive rubber parts division, we provide custom air springs for any vehicle platform. Our truck rubber parts portfolio includes heavy-duty air springs for commercial fleets.

Visit our website at https://www.chuncotechrubber.com/ to request an ozone-resistant air spring consultation or to order samples.