Air disc brakes are relatively rare in the United States, but are abundant in Europe. But high production volumes across the Atlantic have financed the development of excellent products available in the U.S. market.
There are some hurdles to disc use here, including questions about wheel compatibility, significantly higher initial cost and somewhat higher weight. The most frequent U.S. application is on the front axle with certain fleets hauling hazardous materials.
Earlier discs on the steer axle only, or on the tractor but not the trailer, often were incompatible with the drums elsewhere on the rig; they worked too hard and gave short life. But improvements have made hysteresis – apply and release characteristics – more like drums, so work and wear likely are to be shared equally and life expectancy much longer.
In spite of higher first cost, discs promise fade resistance that makes today’s higher highway speeds much safer, leads to long pad life and yields considerably faster, simpler and cheaper brake jobs.
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