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OT: modern semi-trucks brakes

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  • #46
    Yes when you stop and think about not only the sluggish response inherent to air but also the cushioning effect that air has on the system you can quickly visualize why it would be hard to pulse the system rapidly enough to impart the same reaction that hydraulic ABS does.
    A quick analogy would be the effect a water hammer arrester has on it's ability to quell water pressure spikes, all it takes is a small amount of air to dampen the pressure spikes.

    Truck air brake system incorporate a number of relay valves and quick release valves to speed up the response times of application and release pressure and volume. However as good as they are for their intended purpose they can never approach the speed of a fluid that is essentially non-compressible.

    I do have one older 3/4 ton truck with hydraulic drums at the rear that a rear axle only ABS and it works surprisingly well. It is very nose heavy being a diesel powered truck, this combined with large drums at the back to handle it's rated payload capacity gives me ample opportunity to experience the ABS on wet roads frequently if I'm not careful.

    I'm not surprised that you haven't seen too many of the telltale tire skid marks signs of large trucks that signify it being ABS equipped since the industry has been slow to accept the new technology. Lots of new technologies wanting everybody's attention coming up to the forefront monthly it seems, coupled with an audience that is apprehensive to spend serious money on it unless they can see it being a viable long term choice.
    So everyone sits on the sidelines to see how deep and cold the water is before they jump in. Unlike automobiles trucks and trailers are usually ordered to a buyer's spec to a large extent, hence the slow adoption rate unless the technology has been mandated.
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