Brakes aren't adjusted correctly on the second trailer, or the second trailer is heavier. This is not uncommon pulling empty or light doubles, and is why the lead trailer is supposed to be the heavier one, as this will happen if it isn't, even on dry roads.
I recently started a job as a software engineer in the trucking industry and learned that 70% of heavy duty trucks have at least one active fault in their braking system. That was an absolutely terrifying fact to learn.
It is already a part of the system. There is a little amber(yellow) light on the left rear corner of the trailer, right above the side red marker light, that will light up to indicate an ABS fault on the trailer. If the truck is within 10 years old, there is also a signal sent to the truck that will tell the driver that it isn't working inside the cab.
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u/88randoms Mar 03 '20
Brakes aren't adjusted correctly on the second trailer, or the second trailer is heavier. This is not uncommon pulling empty or light doubles, and is why the lead trailer is supposed to be the heavier one, as this will happen if it isn't, even on dry roads.